Copper(I) alkynyl complexes have attracted tremendous attention in structural studies, as luminescent materials, and in catalysis, and homoleptic complexes have been reported to form polymers or large clusters. Herein, six unprecedented structures of Cu^I alkynyl complexes and a procedure to measure the cone angles of alkynyl ligands based on the crystal structures of these complexes are reported. An increase of the alkynyl cone angle in the complexes leads to a modulation of the structures from polymeric [((PhC≡CC≡C)Cu)₂(NH₃)]_∞, to a large cluster [(TripC≡CC≡C)Cu]₂₀(MeCN)₄, to a relatively small cluster [(TripC≡C)Cu]₈ (Trip=2,4,6-iPr₃-C₆H₂). The complexes exhibit yellow-to-red phosphorescence at ambient temperature in the solid state and the luminescence behavior of the Cu₂₀ cluster is sensitive to acetonitrile.

The development of environmentally benign catalysts for highly enantioselective asymmetric cis-dihydroxylation (AD) of alkenes with broad substrate scope remains a challenge. By employing [Fe^II(L)(OTf)₂] (L=N,N′-dimethyl-N,N′-bis(2-methyl-8-quinolyl)-cyclohexane-1,2-diamine) as a catalyst, cis-diols in up to 99.8 % ee with 85 % isolated yield have been achieved in AD of alkenes with H₂O₂ as an oxidant and alkenes in a limiting amount. This “[Fe^II(L)(OTf)₂]+H₂O₂” method is applicable to both (E)-alkenes and terminal alkenes (24 examples >80 % ee, up to 1 g scale). Mechanistic studies, including ¹⁸O-labeling, UV/Vis, EPR, ESI-MS analyses, and DFT calculations lend evidence for the involvement of chiral Fe^III-OOH active species in enantioselective formation of the two C−O bonds.

Copper(I) alkynyl complexes have attracted tremendous attention in structural studies, as luminescent materials, and in catalysis, and homoleptic complexes have been reported to form polymers or large clusters. Herein, six unprecedented structures of Cu^I alkynyl complexes and a procedure to measure the cone angles of alkynyl ligands based on the crystal structures of these complexes are reported. An increase of the alkynyl cone angle in the complexes leads to a modulation of the structures from polymeric [((PhC≡CC≡C)Cu)₂(NH₃)]_∞, to a large cluster [(TripC≡CC≡C)Cu]₂₀(MeCN)₄, to a relatively small cluster [(TripC≡C)Cu]₈ (Trip=2,4,6-iPr₃-C₆H₂). The complexes exhibit yellow-to-red phosphorescence at ambient temperature in the solid state and the luminescence behavior of the Cu₂₀ cluster is sensitive to acetonitrile.

The development of environmentally benign catalysts for highly enantioselective asymmetric cis-dihydroxylation (AD) of alkenes with broad substrate scope remains a challenge. By employing [Fe^II(L)(OTf)₂] (L=N,N′-dimethyl-N,N′-bis(2-methyl-8-quinolyl)-cyclohexane-1,2-diamine) as a catalyst, cis-diols in up to 99.8 % ee with 85 % isolated yield have been achieved in AD of alkenes with H₂O₂ as an oxidant and alkenes in a limiting amount. This “[Fe^II(L)(OTf)₂]+H₂O₂” method is applicable to both (E)-alkenes and terminal alkenes (24 examples >80 % ee, up to 1 g scale). Mechanistic studies, including ¹⁸O-labeling, UV/Vis, EPR, ESI-MS analyses, and DFT calculations lend evidence for the involvement of chiral Fe^III-OOH active species in enantioselective formation of the two C−O bonds.

Identification of the molecular target(s) of anticancer metal complexes is a formidable challenge since most of them are unstable toward ligand exchange reaction(s) or biological reduction under physiological conditions. Gold(III) meso-tetraphenylporphyrin (gold-1 a) is notable for its high stability in biological milieux and potent in vitro and in vivo anticancer activities. Herein, extensive chemical biology approaches employing photo-affinity labeling, click chemistry, chemical proteomics, cellular thermal shift, saturation-transfer difference NMR, protein fluorescence quenching, and protein chaperone assays were used to provide compelling evidence that heat-shock protein 60 (Hsp60), a mitochondrial chaperone and potential anticancer target, is a direct target of gold-1 a in vitro and in cells. Structure–activity studies with a panel of non-porphyrin gold(III) complexes and other metalloporphyrins revealed that Hsp60 inhibition is specifically dependent on both the gold(III) ion and the porphyrin ligand.

Identification of the molecular target(s) of anticancer metal complexes is a formidable challenge since most of them are unstable toward ligand exchange reaction(s) or biological reduction under physiological conditions. Gold(III) meso-tetraphenylporphyrin (gold-1 a) is notable for its high stability in biological milieux and potent in vitro and in vivo anticancer activities. Herein, extensive chemical biology approaches employing photo-affinity labeling, click chemistry, chemical proteomics, cellular thermal shift, saturation-transfer difference NMR, protein fluorescence quenching, and protein chaperone assays were used to provide compelling evidence that heat-shock protein 60 (Hsp60), a mitochondrial chaperone and potential anticancer target, is a direct target of gold-1 a in vitro and in cells. Structure–activity studies with a panel of non-porphyrin gold(III) complexes and other metalloporphyrins revealed that Hsp60 inhibition is specifically dependent on both the gold(III) ion and the porphyrin ligand.

Two classes of pincer-type Pt^II complexes containing tridentate N-donor ligands (1–8) or C-deprotonated N^C^N ligands derived from 1,3-di(2-pyridyl)benzene (10–13) and auxiliary N-heterocyclic carbene (NHC) ligand were synthesized. [Pt(trpy)(NHC)]²⁺ complexes 1–5 display green phosphorescence in CH₂Cl₂ (Φ: 1.1–5.3 %; τ: 0.3–1.0 μs) at room temperature. Moderate-to-intense emissions are observed for 1–7 in glassy solutions at 77 K and for 1–6 in the solid state. The [Pt(N^C^N)(NHC)]⁺ complexes 10–13 display strong green phosphorescence with quantum yields up to 65 % in CHCl₃. The reactions of 1 with a wide variety of anions were examined in various solvents. The tridentate N-donor ligand of 1 undergoes displacement reaction with CN⁻ in protic solvents. Similar displacement of the N^C^N ligand by CN⁻ has been observed for 10, leading to a luminescence “switch-off” response. The water-soluble 7 containing anthracenyl-functionalized NHC ligand acts as a light “switch-on” sensor for the detection of CN⁻ ion with high selectivity. The in vitro cytotoxicity of the Pt^II complexes towards HeLa cells has been evaluated. Complex 12 showed high cytotoxicity with IC₅₀ value of 0.46 μM, whereas 1–4 and 6–8 are less cytotoxic. The cellular localization of the strongly luminescent complex 12 traced by using emission microscopy revealed that it mainly localizes in the cytoplasmic structures rather than in the nucleus. This complex can induce mitochondria dysfunction and subsequent cell death.

Two cytotoxic iron(II) complexes [Fe(L)(CH₃CN)_n](ClO₄)₂ (L=qpy for Fe-1 a, Py₅-OH for Fe-2 a) were synthesized. Both complexes are stable against spontaneous demetalation and oxidation in buffer solutions. Cyclic voltammetry measurements revealed the higher stability of Fe-2 a (+0.82 V vs Fc) against Fe^II to Fe^III oxidation than Fe-1 a (+0.57 V vs Fc). These two complexes display potent cytotoxicity at micromolar level against a panel of cancer cell lines (Fe-1 a=0.8–3.1 μM; Fe-2 a=0.6–3.4 μM), and induce apoptosis that involves caspase activation. Transcriptomic and Connectivity Map analyses revealed that the changes of gene expression induced by Fe-1 a and Fe-2 a are similar to that induced by ciclopirox, an antifungal compound whose mode of action involves formation of intracellular cytotoxic iron chelates. Both Fe-1 a and Fe-2 a caused cellular nuclear DNA damage, as revealed by Comet assay and H2 AX immunofluorescence experiments. The cytotoxicity is associated with production of reactive oxygen species (for Fe-1 a), cell cycle regulation, and stress kinase pathways. The relative contributions of these to the overall cytotoxic mechanism is significantly affected by the structure of penta-N-donor ligand.

Luminescent pincer-type Pt^II complexes supported by C-deprotonated π-extended tridentate RC^N^NR′ ligands and pentafluorophenylacetylide ligands show emission quantum yields up to almost unity. Femtosecond time-resolved fluorescence measurements and time-dependent DFT calculations together reveal the dependence of excited-state structural distortions of [Pt(RC^N^NR′)(CC-C₆F₅)] on the positional isomers of the tridentate ligand. Pt complexes [Pt(R-C^N^NR′)(CC-Ar)] are efficient photocatalysts for visible-light-induced reductive CC bond formation. The [Pt(R-C^N^NR′)(CC-C₆F₅)] complexes perform strongly as phosphorescent dopants for green- and red-emitting organic light-emitting diodes (OLEDs) with external quantum efficiency values over 22.1 %. These complexes are also applied in two-photon cellular imaging when incorporated into mesoporous silica nanoparticles (MSNs).

Luminescent pincer-type Pt^II complexes supported by C-deprotonated π-extended tridentate RC^N^NR′ ligands and pentafluorophenylacetylide ligands show emission quantum yields up to almost unity. Femtosecond time-resolved fluorescence measurements and time-dependent DFT calculations together reveal the dependence of excited-state structural distortions of [Pt(RC^N^NR′)(CC-C₆F₅)] on the positional isomers of the tridentate ligand. Pt complexes [Pt(R-C^N^NR′)(CC-Ar)] are efficient photocatalysts for visible-light-induced reductive CC bond formation. The [Pt(R-C^N^NR′)(CC-C₆F₅)] complexes perform strongly as phosphorescent dopants for green- and red-emitting organic light-emitting diodes (OLEDs) with external quantum efficiency values over 22.1 %. These complexes are also applied in two-photon cellular imaging when incorporated into mesoporous silica nanoparticles (MSNs).

Amination of CH bonds catalyzed by transition metal complexes via nitrene/imide insertion is an appealing strategy for CN bond formation, and the use of iminoiodinanes, or their in situ generated forms from ‘PhI(OAc)₂+primary amides (such as sulfonamides, sulfamates, and carbamates)’, as nitrogen sources for the amination reaction has been well documented. In this work, a ‘metal catalyst+PhI(OAc)₂+primary arylamines’ amination protocol has been developed using [Fe(F₂₀TPP)Cl] (H₂F₂₀TPP=meso-tetrakis(pentafluorophenyl)porphyrin) as a catalyst. This catalytic method is applicable for both intra- and intermolecular amination of sp² and sp³ CH bonds (>27 examples), affording the amination products, including natural products such as rutaecarpine, in moderate-to-good yields. ESI-MS analysis and DFT calculations lend support for the involvement of {[Fe(F₂₀TPP)(NC₆H₄-p-NO₂)](PhI=NC₆H₄-p-NO₂)} intermediate in the catalysis.

The therapeutic applications of many anticancer or antimicrobial metal complexes often suffer from low solubility and low stability in physiological conditions or from drug resistance. To circumvent these problems, nanoparticle systems that allow controlled release and specific accumulation in the targeted disease tissue are of advantage for efficient treatment with minimal toxicity. The focus of this Research News is metal-based nanomaterials comprising anticancer gold(III)/platinum(II) complexes or antimicrobial silver, highlighting the controlled-release properties of self-assembled metal systems.

While the use of molecular materials having long-lived triplet excited state(s) for harvesting solar energy could be an effective approach to boost up the power conversion efficiency (PCE) of organic solar cells (OSCs), the performances of this kind of OSCs as reported in the literature are low (< 2.9% PCE attained for the vacuum-deposited OSCs). Herein is described the realization of high performance OSCs by using gold(III) 5,10,15-triphenylcorrole (Au-C1), gold(III) 10-(p-trifluoromethylphenyl)-5,15-diphenylcorrole (Au-C2), and gold(III) 10-(pentafluorophenyl)-5,15-diphenyl-corrole (Au-C3), as electron-donors. These gold(III) corroles display excited state lifetimes of ≥ 25 μs and low emission quantum yields of < 0.15%. With the complexes Au-C1, Au-C2, and Au-C3, vacuum-deposited OSCs, which give PCEs of 2.7%, 3.0%, and 1.8%, respectively, are fabricated. The PCE can be further boosted up to 4.0% after thermal treatment of the OSC devices. Meanwhile, a solution-processed OSC based on Au-C2 with a high PCE of 6.0% is fabricated. These PCE values are among the best reported for both types of vacuum-deposited and solution-processed OSCs fabricated with metal-organic complexes having long-lived excited states as electron-donor material. The underlying mechanism for the inferior performance of the reported OSCs is discussed.

DFT calculations are performed on [Ru^II(bpy)₂(tmen)]²⁺ (M1, tmen=2,3-dimethyl-2,3-butanediamine) and [Ru^II(bpy)₂(heda)]²⁺ (M2, heda=2,5-dimethyl-2,5-hexanediamine), and on the oxidation reactions of M1 to give the CC bond cleavage product [Ru^II(bpy)₂(NH=CMe₂)₂]²⁺ (M3) and the NO bond formation product [Ru^II(bpy)₂(ONCMe₂CMe₂NO)]²⁺ (M4). The calculated geometrical parameters and oxidation potentials are in good agreement with the experimental data. As revealed by the DFT calculations, [Ru^II(bpy)₂(tmen)]²⁺ (M1) can undergo oxidative deprotonation to generate Ru-bis(imide) [Ru(bpy)₂(tmen-4 H)]⁺ (A) or Ru-imide/amide [Ru(bpy)₂(tmen-3 H)]²⁺ (A′) intermediates. Both A and A′ are prone to CC bond cleavage, with low reaction barriers (ΔG^≠) of 6.8 and 2.9 kcal mol⁻¹ for their doublet spin states ²A and ²A′, respectively. The calculated reaction barrier for the nucleophilic attack of water molecules on ²A′ is relatively high (14.2 kcal mol⁻¹). These calculation results are in agreement with the formation of the Ru^II-bis(imine) complex M3 from the electrochemical oxidation of M1 in aqueous solution. The oxidation of M1 with Ce^IV in aqueous solution to afford the Ru^II-dinitrosoalkane complex M4 is proposed to proceed by attack of the cerium oxidant on the ruthenium imide intermediate. The findings of ESI-MS experiments are consistent with the generation of a ruthenium imide intermediate in the course of the oxidation.

A theoretical investigation on the luminescence efficiency of a series of d⁸ transition-metal Schiff base complexes was undertaken. The aim was to understand the different photophysics of [M-salen]ⁿ complexes (salen=N,N′-bis(salicylidene)ethylenediamine; M=Pt, Pd (n=0); Au (n=+1)) in acetonitrile solutions at room temperature: [Pt-salen] is phosphorescent and [Au-salen]⁺ is fluorescent, but [Pd-salen] is nonemissive. Based on the calculation results, it was proposed that incorporation of electron-withdrawing groups at the 4-position of the Schiff base ligand should widen the ³MLCT–³MC gap (MLCT=metal-to-ligand charge transfer and MC=metal centered, that is, the dd excited state); thus permitting phosphorescence of the corresponding Pd^II Schiff base complex. Although it is experimentally proven that [Pd-salph-4E] (salph=N,N′-bis(salicylidene)-1,2-phenylenediamine; 4E means an electron-withdrawing substituent at the 4-position of the salicylidene) displays triplet emission, its quantum yield is low at room temperature. The corresponding Pt^II Schiff base complex, [Pt-salph-4E], is also much less emissive than the unsubstituted analogue, [Pt-salph]. Thus, a detailed theoretical analysis of how the substituent and central metal affected the photophysics of [M-salph-X] (X is a substituent on the salph ligand, M=Pt or Pd) was performed. Temperature effects were also investigated. The simple energy gap law underestimated the nonradiative decay rates and was insufficient to account for the temperature dependence of the nonradiative decay rates of the complexes studied herein. On the other hand, the present analysis demonstrates that inclusions of low-frequency modes and the associated frequency shifts are decisive in providing better quantitative estimates of the nonradiative decay rates and the experimentally observed temperature effects. Moreover, spin–orbit coupling, which is often considered only in the context of radiative decay rate, has a significant role in determining the nonradiative rate as well.

A new class of cyclometalated Au^III complexes containing various bidentate C-deprotonated C^N and cis-chelating bis(N-heterocyclic carbene) (bis-NHC) ligands has been synthesized and characterized. These are the first examples of Au^III complexes supported by cis-chelating bis-NHC ligands. [Au(C^N)(bis-NHC)] complexes display emission in solutions under degassed condition at room temperature with emission maxima (λ_max) at 498–633 nm and emission quantum yields of up to 10.1 %. The emissions are assigned to triplet intraligand (IL) ππ* transitions of C^N ligands. The Au^III complex containing a C^N (C-deprotonated naphthalene-substituted quinoline) ligand with extended π-conjugation exhibits prompt fluorescence and phosphorescence of comparable intensity with λ_max at 454 and 611 nm respectively. With sulfonate-functionalized bis-NHC ligand, four water-soluble luminescent Au^III complexes, including those displaying both fluorescence and phosphorescence, were prepared. They show similar photophysical properties in water when compared with their counterparts in acetonitrile. The long phosphorescence lifetime of the water-soluble AuIII complex with C-deprotonated naphthalene-substituted quinoline ligand renders it to function as ratiometric sensor for oxygen. Inhibitory activity of one of these water-soluble Au^III complexes towards deubiquitinase (DUB) UCHL3 has been investigated; this complex also displayed a significant inhibitory activity with IC₅₀ value of 0.15 μM.

A series of ruthenium porphyrins [Ru^IV(por)(NHY)₂] and [Ru^VI(por)(NY)₂] bearing axially coordinated π-conjugated arylamide and arylimide ligands, respectively, have been synthesized. The crystal structures of [Ru^IV(tmp)(NHY)₂] (tmp=5,10,15,20-tetramesitylporphyrinato(2−)) with Y=4′-methoxy-biphenyl-4-yl (ArAr-p-OMe), 4′-chloro-biphenyl-4-yl (ArAr-p-Cl), and 9,9-dibutyl-fluoren-2-yl (Ar^Ar) show axial RuN(arylamide) distances of 1.978(4), 1.971(6), and 1.985(13) Å, respectively. [Ru^IV(tmp)(NH{Ar^Ar})₂] is an example of metalloporphyrins that bind an arylamide ligand featuring a co-planar biphenyl unit. The [Ru^IV(por)(NHY)₂] complexes show a quasi-reversible reduction couple or irreversible reduction wave attributed to Ru^IVRu^III with E_pc from −1.06 to −1.40 V versus Cp₂Fe^+/0 and an irreversible oxidation wave with E_pa from −0.04 to 0.19 V versus Cp₂Fe^+/0. Reaction of the [Ru^IV(por)(NHY)₂] with bromine afforded [Ru^IV(por)(NHY)Br]. PhI(OAc)₂ oxidation of the [Ru^IV(por)(NHY)₂] gave [Ru^VI(por)(NY)₂]; the latter can be prepared from reaction of [Ru^II(por)(CO)] with aryl azides N₃Y. The crystal structure of [Ru^VI(tmp)(N{ArAr-p-OMe})₂] features RuN(arylimide) distances of 1.824(5) and 1.829(5) Å. Alkene aziridination and CH amination catalyzed by “[Ru^II(tmp)(CO)]+π-conjugated aryl azides”, or mediated by [Ru^VI(por)(NY)₂] with Y=biphenyl-4-yl (ArAr) and ArAr-p-Cl, gave aziridines and amines in moderate yields. The electronic structure of [Ru^VI(por)(NY)₂] was examined by DFT calculations.

Bis(NHC)ruthenium(II)–porphyrin complexes were designed, synthesized, and characterized. Owing to the strong donor strength of axial NHC ligands in stabilizing the trans MCRR′/MNR moiety, these complexes showed unprecedently high catalytic activity towards alkene cyclopropanation, carbene CH, NH, SH, and OH insertion, alkene aziridination, and nitrene CH insertion with turnover frequencies up to 1950 min⁻¹. The use of chiral [Ru(D₄-Por)(BIMe)₂] (1 g) as a catalyst led to highly enantioselective carbene/nitrene transfer and insertion reactions with up to 98 % ee. Carbene modification of the N terminus of peptides at 37 °C was possible. DFT calculations revealed that the trans axial NHC ligand facilitates the decomposition of diazo compounds by stabilizing the metal–carbene reaction intermediate.

In the design of anticancer gold(I) complexes with high in vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1-PF₆) utilizing a bridging bis(N-heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1-PF₆ displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In vivo studies reveal that 1-PF₆ significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16-F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in vitro. Toxicology studies indicate that 1-PF₆ does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits.

With a ruthenium–porphyrin catalyst, alkyl diazomethanes generated in situ from N-tosylhydrazones efficiently underwent intramolecular C(sp³)H insertion of an alkyl carbene to give substituted tetrahydrofurans and pyrrolidines in up to 99 % yield and with up to 99:1 cis selectivity. The reaction displays good tolerance of many functionalities, and the procedure is simple without the need for slow addition with a syringe pump. From a synthetic point of view, the CH insertion of N-tosylhydrazones can be viewed as reductive coupling between a CO bond and a CH bond to form a new CC bond, since N-tosylhydrazones can be readily prepared from carbonyl compounds. This reaction was successfully applied in a concise synthesis of (±)-pseudoheliotridane.

Luminescent metallo-intercalators are potent biosensors of nucleic acid structure and anticancer agents targeting DNAs. There are few examples of luminescent metallo-intercalators which can simultaneously act as emission probes of nucleic acid structure and display promising anticancer activities. Herein, we describe a luminescent platinum(II) complex, [Pt(C^N^N)(C≡NtBu)]ClO₄ (1 a, HC^N^N= 6-phenyl-2,2′-bipyridyl), that intercalates between the nucleobases of nucleic acids, accompanied by an increase in emission intensity and/or a significant change in the maximum emission wavelength. The changes in emission properties measured with double-stranded RNA (dsRNA) are different from those with dsDNA used in the binding reactions. Complex 1 a exhibited potent anticancer activity towards cancer cells in vitro and inhibited tumor growth in a mouse model. The stabilization of the topoisomerase I–DNA complex with resulting DNA damage by 1 a is suggested to contribute to its anticancer activity.

Construction of delivery systems for anticancer gold complexes to decrease their toxicity while maintaining efficacy is a key strategy to optimize and develop anticancer gold medicines. Herein, we describe cancer-targeted mesoporous silica nanoparticles (MSN) for delivery of a gold(III) porphyrin complex (Au-1 a@MSN(R)) to enhance its anticancer efficacy and selectivity between cancer and normal cells. Encapsulation of Au-1 a within mesoporous silica nanoparticles amplifies its inhibitory effects on thioredoxin reductase (TrxR), resulting in a loss of redox balance and overproduction of reactive oxygen species (ROS). Elevated cellular oxidative stress activates diversified downstream ROS-mediated signaling pathways, leading to enhanced apoptosis-inducing efficacy.

A series of cyclometalated Pd^II complexes that contain π-extended RC^N^NR′ (RC^N^NR′=3-(6′-aryl-2′-pyridinyl)isoquinoline) and chloride/pentafluorophenylacetylide ligands have been synthesized and their photophysical and photochemical properties examined. The complexes with the chloride ligand are emissive only in the solid state and in glassy solutions at 77 K, whereas the ones with the pentafluorophenylacetylide ligand show phosphorescence in the solid state (λ_max=584–632 nm) and in solution (λ_max=533–602 nm) at room temperature. Some of the complexes with the pentafluorophenylacetylide ligand show emission with λ_max at 585–602 nm upon an increase in the complex concentration in solutions. These Pd^II complexes can act as photosensitizers for the light-induced aerobic oxidation of amines. In the presence of 0.1 mol % Pd^II complex, secondary amines can be oxidized to the corresponding imines with substrate conversions and product yields up to 100 and 99 %, respectively. In the presence of 0.15 mol % Pd^II complex, the oxidative cyanation of tertiary amines could be performed with product yields up to 91 %. The Pd^II complexes have also been used to sensitize photochemical hydrogen production with a three-component system that comprises the Pd^II complex, [Co(dmgH)₂(py)Cl] (dmgH=dimethylglyoxime; py=pyridine), and triethanolamine, and a maximum turnover of hydrogen production of 175 in 4 h was achieved. The excited-state electron-transfer properties of the Pd^II complexes have been examined.

Sterically hindered platinum(II) Schiff base complexes were prepared. Complex 4, which displays red emission with a quantum yield of 0.29 in a thin film and a self-quenching rate constant of 1×10⁻⁷ dm³ mol⁻¹ s⁻¹, was used to fabricate organic light-emitting diodes with single or double emissive layers (EMLs). An iridium(III) complex with a wide band gap was codoped into the electron-dominant EML to act as a deep electron trapper, and red-light-emitting devices with the highest current, power, and external quantum efficiencies of 20.43 cd A⁻¹ 18.33 Lm W⁻¹, and 11.7 %, respectively, were fabricated. A high current efficiency and EQE of up to 14.69 cd A⁻¹ and 8.3 %, respectively, were achieved at a high brightness of 1000 cd m⁻². The significant delay of efficiency roll-off is attributed to the bulky 3D structure of the norbornene moiety at the periphery of the Schiff base ligand of 4 and to the new device design strategy. The fabricated device had a projected lifetime (LT50) of 18 000 h.

With a ruthenium–porphyrin catalyst, alkyl diazomethanes generated in situ from N-tosylhydrazones efficiently underwent intramolecular C(sp³)H insertion of an alkyl carbene to give substituted tetrahydrofurans and pyrrolidines in up to 99 % yield and with up to 99:1 cis selectivity. The reaction displays good tolerance of many functionalities, and the procedure is simple without the need for slow addition with a syringe pump. From a synthetic point of view, the CH insertion of N-tosylhydrazones can be viewed as reductive coupling between a CO bond and a CH bond to form a new CC bond, since N-tosylhydrazones can be readily prepared from carbonyl compounds. This reaction was successfully applied in a concise synthesis of (±)-pseudoheliotridane.

The oxidation of light alkanes that is catalyzed by heme and nonheme iron enzymes is widely proposed to involve highly reactive {Fe^VO} species or {Fe^IVO} ligand cation radicals. The identification of these high-valent iron species and the development of an iron-catalyzed oxidation of light alkanes under mild conditions are of vital importance. Herein, a combination of tridentate and bidentate ligands was used for the generation of highly reactive nonheme {FeO} species. A method that employs [Fe^III(Me₃tacn)(Cl-acac)Cl]⁺ as a catalyst in the presence of oxone was developed for the oxidation of hydrocarbons, including cyclohexane, propane, and ethane (Me₃tacn=1,4,7-trimethyl-1,4,7-triazacyclononane; Cl-acac=3-chloro-acetylacetonate). The complex [Fe^III(Tp)₂]⁺ and oxone enabled stoichiometric oxidation of propane and ethane. ESI-MS, EPR and UV/Vis spectroscopy, ¹⁸O labeling experiments, and DFT studies point to [Fe^IV(Me₃tacn)({Cl-acac}^.+)(O)]²⁺ as the catalytically active species.

Luminescent metallo-intercalators are potent biosensors of nucleic acid structure and anticancer agents targeting DNAs. There are few examples of luminescent metallo-intercalators which can simultaneously act as emission probes of nucleic acid structure and display promising anticancer activities. Herein, we describe a luminescent platinum(II) complex, [Pt(C^N^N)(C≡NtBu)]ClO₄ (1 a, HC^N^N= 6-phenyl-2,2′-bipyridyl), that intercalates between the nucleobases of nucleic acids, accompanied by an increase in emission intensity and/or a significant change in the maximum emission wavelength. The changes in emission properties measured with double-stranded RNA (dsRNA) are different from those with dsDNA used in the binding reactions. Complex 1 a exhibited potent anticancer activity towards cancer cells in vitro and inhibited tumor growth in a mouse model. The stabilization of the topoisomerase I–DNA complex with resulting DNA damage by 1 a is suggested to contribute to its anticancer activity.

In the design of anticancer gold(I) complexes with high in vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1-PF₆) utilizing a bridging bis(N-heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1-PF₆ displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In vivo studies reveal that 1-PF₆ significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16-F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in vitro. Toxicology studies indicate that 1-PF₆ does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits.

The oxidation of light alkanes that is catalyzed by heme and nonheme iron enzymes is widely proposed to involve highly reactive {Fe^VO} species or {Fe^IVO} ligand cation radicals. The identification of these high-valent iron species and the development of an iron-catalyzed oxidation of light alkanes under mild conditions are of vital importance. Herein, a combination of tridentate and bidentate ligands was used for the generation of highly reactive nonheme {FeO} species. A method that employs [Fe^III(Me₃tacn)(Cl-acac)Cl]⁺ as a catalyst in the presence of oxone was developed for the oxidation of hydrocarbons, including cyclohexane, propane, and ethane (Me₃tacn=1,4,7-trimethyl-1,4,7-triazacyclononane; Cl-acac=3-chloro-acetylacetonate). The complex [Fe^III(Tp)₂]⁺ and oxone enabled stoichiometric oxidation of propane and ethane. ESI-MS, EPR and UV/Vis spectroscopy, ¹⁸O labeling experiments, and DFT studies point to [Fe^IV(Me₃tacn)({Cl-acac}^.+)(O)]²⁺ as the catalytically active species.

A new class of charge neutral, strongly luminescent cyclometalated platinum(II) complexes supported by dianionic tetradentate ligand are synthesized. One of these platinum(II) complexes, Y-Pt, displays a high photoluminescence quantum yield of 86% and electroluminescence efficacy (η_power) of up to 52 lm W⁻¹, and is utilized as a yellow phosphorescent dopant in the fabrication of white organic light-emitting devices (WOLEDs). WOLEDs based on conventional structures with yellow emission from Y-Pt in combination with blue emission from bis(4,6-difluorophenyl-pyridinato-N,C²′) (picolinate) iridium(III) (FIrpic) show a total η_power of up to 31 lm W⁻¹. A two-fold increase in η_power by utilizing a modified WOLED structure comprising of a composite blue host is realized. With this modified device structure, the total η_power and driving voltage at a luminance of 1000 cd m⁻² can be improved to 61 lm W⁻¹ and 7.5 V (i.e., 10 V for control devices). The performance improvement is attributed to an effectively broaden exciton formation-recombination zone and alleviation of localized exciton accumulation within the FIrpic-doped composite host for reduced triplet-triplet annihilation, yielding blue light-emission with enhanced intensity. The modified device structure can also adopt a higher concentration of Y-Pt towards its optimal value, leading to WOLEDs with high efficiency.

A series of palladium(II)–porphyrin complexes that display dual emissions with lifetimes up to 437 μs have been synthesized. Among the four complexes, PdF₂₀TPP is an efficient and robust catalyst for photoinduced oxidative CH functionalization by using oxygen as terminal oxidant. α-Functionalized tertiary amines were obtained in good to excellent yields by light irradiation (λ>400 nm) of a mixture of PdF₂₀TPP, tertiary amine, and nucleophile (cyanide, nitromethane, dimethyl malonate, diethyl phosphite, and acetone) under aerobic conditions. Four examples of intramolecular cyclized amine compounds could be similarly prepared. Comparison of the UV-visible absorption spectra before and after the photochemical reaction revealed that PdF₂₀TPP was highly robust (>95 % recovery). The practical application of PdF₂₀TPP has been revealed by the photochemical reactions performed by using a low catalyst loading (0.01 mol %) and on a 10 mmol scale. The PdF₂₀TPP catalyst could sensitize photoinduced oxidation of sulfides to sulfoxides in excellent yields. Mechanistic studies revealed that the photocatalysis proceeded by singlet-oxygen oxidation.

The X-ray crystal structure of [Ru^VI(NMs)₂(tmp)] (Ms=SO₂- p-MeOC₆H₄; tmp=5,10,15,20-tetramesitylporphyrinato(2−)), a metal sulfonylimide complex that can undergo alkene aziridination and CH bond amination reactions, shows a RuN distance of 1.79(3) Å and Ru-N-S angle of 162.5(3)°. Density functional theory (DFT) calculations on the electronic structures of [Ru^VI(NMs)₂(tmp)] and model complex [Ru^VI(NMs)₂(por⁰)] (por⁰=unsubstituted porphyrinato(2−)) using the M06L functional gave results in agreement with experimental observations. For the amination of ethylbenzene by the singlet ground state of [Ru^VI(NMs)₂(por⁰)], DFT calculations using the M06L functional revealed an effectively concerted pathway involving rate-limiting hydrogen atom abstraction without a distinct radical rebound step. The substituent effect on the amination reactivity of ethylbenzene by [Ru^VI(NX)₂(por⁰)] (X=SO₂-p-YC₆H₄ with Y=MeO, Me, H, Cl, NO₂) was examined. Electron-withdrawing Y groups lower the energy of the LUMOs of [Ru^VI(NX)₂(por⁰)], thus facilitating their interaction with the low-lying HOMO of the ethylbenzene CH bond and hence increasing the reactivity of [Ru^VI(NX)₂(por⁰)]. DFT calculations on the amination/aziridination reactions of [Ru^VI(NSO₂C₆H₅)₂(por⁰)] with pent-4-enal, an aldehyde substrate bearing acyl, homoallylic, and allylic CH bonds and a CC bond, revealed a lower reaction barrier for the amination of the acyl CH bond than for both the amination of the other CH bonds and aziridination of the CC bond in this substrate.

The electronic structure and redox properties of the highly oxidizing, isolable Ru^VO complex [Ru^V(N₄O)(O)]²⁺, its oxidation reactions with saturated alkanes (cyclohexane and methane) and inorganic substrates (hydrochloric acid and water), and its intermolecular coupling reaction have been examined by DFT calculations. The oxidation reactions with cyclohexane and methane proceed through hydrogen atom transfer in a transition state with a calculated free energy barrier of 10.8 and 23.8 kcal mol⁻¹, respectively. The overall free energy activation barrier (ΔG^≠=25.5 kcal mol⁻¹) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of [Ru^III(N₄O)(HOCl)]²⁺ (ΔG=15.0 kcal mol⁻¹) and the substitution of HOCl by a water molecule (ΔG^≠=10.5 kcal mol⁻¹). For water oxidation, nucleophilic attack on Ru^VO by water, leading to OO bond formation, has a free energy barrier of 24.0 kcal mol⁻¹, the major component of which comes from the cleavage of the HOH bond of water. Intermolecular self-coupling of two molecules of [Ru^V(N₄O)(O)]²⁺ leads to the [(N₄O)Ru^IVO₂Ru^III(N₄O)]⁴⁺ complex with a calculated free energy barrier of 12.0 kcal mol⁻¹.

The bis(azido)ruthenium(III) complexes, trans-[Ru(L)(N₃)₂]⁺ [L = 14-TMC (1) and 16-TMC (4)] have been prepared. These complexes undergo facile thermal or photo-decomposition in RCN (R = Me, Bu, Ph, 4-MePh, 2-MeOPh) solutions to produce the corresponding azidoruthenium(II) complexes trans-[Ru(L)(N₃)(RCN)]⁺ [L = 14-TMC, R = Me (2a), Bu (2b), Ph (2c), 4-MePh (2d), 2-MeOPh (2e); L = 16-TMC, R = Me (5a), = Ph (5b)] and cis-[Ru(Tet-Me₆)(N₃)(MeCN)]⁺ (6). Complex 1 reacted with PPh₃, by a nitrogen atom transfer reaction, to give trans-[Ru(14-TMC)(N₃)(NPPh₃)]⁺ (3) in 80 % yield. The crystal structures of 2e(PF₆), 3(PF₆) and 5b(ClO₄) have been determined by X-ray diffraction analysis. Complex 3 is the first structurally characterized (phosphoraniminato)ruthenium(III) complex with Ru–N distances of 1.991(7)–2.014(6) Å and a nearly linear Ru–N–P moiety [[ang]Ru–N–P = 168.2(5)–171.5(6)°]. Density functional theory (DFT) calculations on 3 and the proposed [Ru^V(14-TMC)(N)(N₃)]⁺ intermediate have been performed.

A series of [(R′-C^N^C-R′′)Pt(L)] complexes with doubly deprotonated cyclometalated R′-C^N^C-R′′ ligands (R′-C^N^C-R′′=2,6-diphenylpyridine derivatives) functionalized with carbazole, fluorene, or thiophene unit(s) have been synthesized and their photophysical properties studied. The X-ray crystal structures reveal extensive intermolecular π⋅⋅⋅π and CH⋅⋅⋅π interactions between the cyclometalated C^N^C ligands. Compared to previously reported cyclometalated platinum(II) complexes [(C^N^C)Pt(L)], which are non-emissive in solution at room temperature, the carbazole-, fluorene- and thiophene-functionalized [(R′-C^N^C-R′′)Pt(L)] (L=DMSO 1–9, CNAr, 1 a–9 a) complexes are emissive in solution at room temperature with λ_max at 564–619 nm and Φ=0.02–0.26. The emissions of the [(R′-C^N^C-R′′)Pt(L)] complexes are attributed to electronic excited states with mixed ³MLCT and ³IL character. The carbazole/fluorene/thiophene unit(s) allow the tuning of the electronic properties of the [(R′-C^N^C-R′′)Pt] moiety, with the emission maxima in a range of 564–619 nm. These are the first examples of organoplatinum(II) complexes bearing doubly deprotonated cyclometalated C^N^C ligands that are emissive in solution at room temperature. In non-degassed DMSO, the emission intensities of 6 a–9 a are enhanced upon exposure to ambient light. This phenomenon is caused by reacting photogenerated ¹O₂ with a DMSO molecule to form dimethyl sulfone, leading to the removal of dissolved oxygen in solution. Self-assembled nanowires and nanorods are obtained from precipitation of 3 a in THF/H₂O and 8 a in DMSO/Et₂O, respectively. The [(R′-C^N^C-R′′)Pt(L)] complexes are soluble in common organic solvents with a high thermal stability (>300 °C), rendering them as phosphorescent dopants for organic light-emitting diode (OLEDs) applications. Red OLEDs with CIE coordinates of (0.65±0.01, 0.35±0.01) were fabricated from 7 a or 8 a. A maximum external efficiency (η_Ext) of 12.6 % was obtained for the device using 8 a as emitter.

Ru₃(TSA)₆ (1; H₂TSA=2-thiosalicylic acid), which bears six peripheral carboxylate groups and was isolated in the form [NEt₄]_1.5[Ru₃(HTSA)₂(TSA)₄](OAc)_0.5⋅3.5 H₂O, serves as a building block for assembly of heterometallic coordination polymers. Treatment of 1 with [Fe(acac)₃] (acac=acetylacetonate) in EG/H₂O (EG=ethylene glycol) afforded 1D Ru₃–Fe coordination polymer 2 by means of the connection of the building block 1 through iron centers. Treatment of 1 with MnCl₂ in EG resulted in the formation of 1D Ru₃–Mn₃ coordination polymer 3, which features self-assembled polynuclear linking units Mn₃(OCH₂CH₂O)₃, each of which contains a planar Mn₃O₃ ring. By treating 1 with Gd(NO₃)₃ and NaHCO₃ in EG, a 3D Ru₃–Gd₆ coordination polymer 4 was obtained; this 3D coordination polymer features unprecedented Gd₆(μ₃-CO₃)₄ units. The magnetic properties of 1–4, along with DFT calculations on the electronic structure of 1, are also described.

An efficient method for the synthesis of tertiary amines through a gold(I)-catalyzed tandem reaction of alkynes with secondary amines has been developed. In the presence of ethyl Hantzsch ester and [{(tBu)₂(o-biphenyl)P}AuCl]/AgBF₄ (2 mol %), a variety of secondary amines bearing electron-deficient and electron-rich substituents and a wide range of alkynes, including terminal and internal aryl alkynes, aliphatic alkynes, and electron-deficient alkynes, underwent a tandem reaction to afford the corresponding tertiary amines in up to 99 % yield. For indolines bearing a preexisting chiral center, their reactions with alkynes in the presence of ethyl Hantzsch ester catalyzed by [{(tBu)₂(o-biphenyl)P}AuCl]/AgBF₄ (2 mol %) afforded tertiary amines in excellent yields and with good to excellent diastereoselectivity. All of these organic transformations can be conducted as a one-pot reaction from simple and readily available starting materials without the need of isolation of air/moisture-sensitive enamine intermediates, and under mild reaction conditions (mostly room temperature and mild reducing agents). Mechanistic studies by NMR spectroscopy, ESI-MS, isotope labeling studies, and DFT calculations on this gold(I)-catalyzed tandem reaction reveal that the first step involving a monomeric cationic gold(I)–alkyne intermediate is more likely than a gold(I)–amine intermediate, a three-coordinate gold(I) intermediate, or a dinuclear gold(I)–alkyne intermediate. These studies also support the proposed reaction pathway, which involves a gold(I)-coordinated enamine complex as a key intermediate for the subsequent transfer hydrogenation with a hydride source, and reveal the intrinsic stereospecific nature of these transformations observed in the experiments.

Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8-hydroxyquinoline (Hq) or 5,7-dimethyl-8-hydroxy-quinoline (HMe₂q) as an electron donor were fabricated by vacuum deposition. The bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) [Pt(Me₂q)₂]-based OPVs showed the best performance with an open voltage (V_OC) of 0.42 V, a short circuit current density (J_SC) of 14.8 mA cm⁻², and a maximum power conversion efficiency (η_P) of 2.4 %. The X-ray single-crystal structures together with the grazing incidence X-ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as-fabricated field-effect transistors (FETs) and OPV cells.

Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90 %) and with moderate enantioselectivities (up to 63 % ee). Among the gold(I) complexes examined, better ee values were obtained with binuclear gold(I) complexes, which displayed intramolecular Au^IAu^I interactions. The binuclear gold(I) complex 4c [(AuCl)₂(L3)] with chiral biaryl phosphine ligand (S)-(−)-MeO-biphep (L3) is the most efficient catalyst and gives the best ee value of up to 63 %. Substituents on the allene reactants have a slight effect on the enantioselectivity of the reaction. Electron-withdrawing groups on the indole substrates decrease the enantioselectivity of the reaction. The relative reaction rates of the hydroarylation of 4-X-substituted 1,3-diarylallenes with N-methylindole in the presence of catalyst 4c [(AuCl)₂(L3)]/AgOTf [L3=(S)-(−)-MeO-biphep], determined through competition experiments, correlate (r²=0.996) with the substituent constants σ. The slope value is −2.30, revealing both the build-up of positive charge at the allene and electrophilic nature of the reactive Au^I species. Two plausible reaction pathways were investigated by density functional theory calculations, one pathway involving intermolecular nucleophilic addition of free indole to aurated allene intermediate and another pathway involving intramolecular nucleophilic addition of aurated indole to allene via diaurated intermediate E2. Calculated results revealed that the reaction likely proceeds via the first pathway with a lower activation energy. The role of Au^IAu^I interactions in affecting the enantioselectivity is discussed.

A silica-supported gold nanoparticle catalyst AuNPs/SiO₂ (A) has been prepared by deposition of in situ synthesized gold nanoparticles (AuNPs) onto the surface of silica. A simple method that uses A as the catalyst and oxygen as the oxidant is effective for oxidative cyclization of anilines with aldehydes to form quinolines in a one-pot reaction (20 examples; product yields up to 95 %). The “AuNPs/SiO₂+O₂” protocol is applicable to the synthesis of nitrogen-containing polyheterocyclic compounds in good to excellent product yields by using bulky polycyclic anilines as the starting materials (10 examples; product yields up to 96 %). The A catalyst can be easily recovered by centrifugation and reused for seven consecutive runs without significant loss of catalytic activity.

A new method was developed to transform alkenes into three types of functional molecules, including epoxides, aldehydes and 1,2-diols by using dichlororuthenium(IV) meso-tetrakis(2,6-dichlorophenyl)porphyrin [Ru(IV)(TDCPP)Cl₂] as catalyst and 2,6-dichloropyridine N-oxide (Cl₂pyNO) as the oxidant, in which the 1,2-diols were afforded via “one-pot” reactions in moderate yields.

Density functional theory (DFT) studies were carried out on [Fe(O)₂(L)]ⁿ⁺ [L = qpy (1), simple amines (2), and tpy (3); qpy = 2,2′:6′,2″:6″,2″′:6″′,2″″-quinquepyridine and tpy = terpyridine; n = 1 or 2] to study how the coordination number of the spectator ligand L affects the geometries and electronic structures of the complexes. It was found that qpy can act as both a tridentate and pentadentate ligand resulting in [Fe(O)₂(qpy)]²⁺ (1²⁺) having a trigonal bipyramidal (TBP) geometry in the former case, and a pentagonal bipyramidal (PBP) geometry in the latter case. The difference in coordination geometries has a significant impact on the electronic structures of 1²⁺. With a TBP geometry, 1²⁺ adopts a [Fe^V(O)₂(qpy)^+·]²⁺ formalism where a d³ quartet Fe^V ion ferromagnetically and antiferromagnetically couples to the qpy cation radical to give close-lying triplet and quintet states (within ca. 0.2 eV). With a PBP geometry, the Fe^V ion in 1²⁺ also formally has three unpaired electrons (a d³ quartet) with the fourth unpaired electron localized on a single oxido ligand to give a quintet state. The unoccupied orbital of 1²⁺ in PBP geometry is lower lying in energy and has higher oxido character than when the complex has TBP geometry. Thus, based on the MO energies and oxido character of the unoccupied orbital, 1²⁺ with PBP geometry is proposed to be a more reactive oxidant than 1²⁺ with TBP geometry. On the other hand, 1²⁺ with TBP geometry has a similar electronic structure to heme Cpd I, and it is possible that these two compounds have similar oxygen atom transfer reaction mechanisms. By varying the ligand coordination number using different spectator ligands L, the dioxido-iron complex [Fe(O)₂(L)]²⁺ can change from a high-spin triplet when L = tpy, to a low-spin singlet when L = simple amines, to a quasi-degenerate triplet and quintet state when L = qpy.

[Fe^III(F₂₀-tpp)Cl] (F₂₀-tpp=meso-tetrakis(pentafluorophenyl)porphyrinato dianion) is an effective catalyst for imido/nitrene insertion reactions using sulfonyl and aryl azides as nitrogen source. Under thermal conditions, aziridination of aryl and alkyl alkenes (16 examples, 60–95 % yields), sulfimidation of sulfides (11 examples, 76–96 % yields), allylic amidation/amination of α-methylstyrenes (15 examples, 68–83 % yields), and amination of saturated CH bonds including that of cycloalkanes and adamantane (eight examples, 64–80 % yields) can be accomplished by using 2 mol % [Fe^III(F₂₀-tpp)Cl] as catalyst. Under microwave irradiation conditions, the reaction time of aziridination (four examples), allylic amination (five examples), sulfimidation (two examples), and amination of saturated CH bonds (three examples) can be reduced by up to 16-fold (24–48 versus 1.5–6 h) without significantly affecting the product yield and substrate conversion.

A series of platinum(II) complexes bearing tridentate cyclometalated C^N^N (C^N^N=6-phenyl-2,2'-bipyridine and π-extended R-C^N^N=3-[6'-(naphthalen-2''-yl)pyridin-2'-yl]isoquinoline) ligands with fluorene units have been synthesised and their photophysical properties have been studied. The fluorene units are incorporated into the cyclometalated ligands by a Suzuki coupling reaction. An increase in the π-conjugation of the cyclometalated ligands confers favourable photophysical properties compared to the 6-phenyl-2,2'-bipyridine analogues. The fluorene-based platinum(II) complexes display vibronic-structured emission bands with λ_max=558–601 nm, and high emission quantum yields up to 0.76 in degassed dichloromethane. Their emissions are tentatively assigned to excited states with mixed ³IL/³MLCT parentage (IL=intraligand, MLCT=metal-to-ligand charge transfer). The crystal structures of these platinum(II) complexes reveal extensive Pt^II⋅⋅⋅π and/or π–π interactions. The fluorene-based platinum(II) complexes are soluble in organic solvents, have high thermal stability with decomposition temperature >350 °C, and can be thermally vacuum-sublimed or solution-processed as phosphorescent dopants for the fabrication of organic light-emitting diodes (OLEDs). A monochromic OLED with 3 d as dopant (2 wt %) fabricated by vacuum deposition gave a current efficiency of 14.7 cd A⁻¹ and maximum brightness of 27000 cd m⁻². A high current efficiency (9.2 cd A⁻¹) has been achieved in a solution-processed OLED using complex 3 f (5 wt %) doped in a PVK (poly(9-vinylcarbazole)) host.

In the design of physiologically stable anticancer gold(III) complexes, we have employed strongly chelating porphyrinato ligands to stabilize a gold(III) ion [Chem. Commun. 2003, 1718; Coord. Chem. Rev.2009, 253, 1682]. In this work, a family of gold(III) tetraarylporphyrins with porphyrinato ligands containing different peripheral substituents on the meso-aryl rings were prepared, and these complexes were used to study the structure–bioactivity relationship. The cytotoxic IC₅₀ values of [Au(Por)]⁺ (Por=porphyrinato ligand), which range from 0.033 to >100 μM, correlate with their lipophilicity and cellular uptake. Some of them induce apoptosis and display preferential cytotoxicity toward cancer cells than to normal noncancerous cells. A new gold(III)–porphyrin with saccharide conjugation [Au(4-glucosyl-TPP)]Cl (2 a; H₂(4-glucosyl-TPP)=meso-tetrakis(4-β-D-glucosylphenyl)porphyrin) exhibits significant cytostatic activity to cancer cells (IC₅₀=1.2–9.0 μM) without causing cell death and is much less toxic to lung fibroblast cells (IC₅₀>100 μM). The gold(III)–porphyrin complexes induce S-phase cell-cycle arrest of cancer cells as indicated by flow cytometric analysis, suggesting that the anticancer activity may be, in part, due to termination of DNA replication. The gold(III)–porphyrin complexes can bind to DNA in vitro with binding constants in the range of 4.9×10⁵ to 4.1×10⁶ dm³ mol⁻¹ as determined by absorption titration. Complexes 2 a and [Au(TMPyP)]Cl₅ (4 a; [H₂TMPyP]⁴⁺=meso-tetrakis(N-methylpyridinium-4-yl)porphyrin) interact with DNA in a manner similar to the DNA intercalator ethidium bromide as revealed by gel mobility shift assays and viscosity measurements. Both of them also inhibited the topoisomerase I induced relaxation of supercoiled DNA. Complex 4 a, a gold(III) derivative of the known G-quadruplex-interactive porphyrin [H₂TMPyP]⁴⁺, can similarly inhibit the amplification of a DNA substrate containing G-quadruplex structures in a polymerase chain reaction stop assay. In contrast to these reported complexes, complex 2 a and the parental gold(III)–porphyrin 1 a do not display a significant inhibitory effect (<10 %) on telomerase. Based on the results of protein expression analysis and computational docking experiments, the anti-apoptotic bcl-2 protein is a potential target for those gold(III)–porphyrin complexes with apoptosis-inducing properties. Complex 2 a also displays prominent anti-angiogenic properties in vitro. Taken together, the enhanced stabilization of the gold(III) ion and the ease of structural modification render porphyrins an attractive ligand system in the development of physiologically stable gold(III) complexes with anticancer and anti-angiogenic activities.

Platinum(II) complexes bearing acetylide ligands containing nucleobase motifs are prepared and their impact on human topoisomerase II (TopoII) is evaluated. Both platinum(II) complexes [Pt^II(C^N^N)(C≡CCH₂R)] (1a, 1b, 1c) and [Pt^II(tBu₃terpy)(C≡CCH₂R)]⁺ (2a, 2b, 2c) (C^N^N=6-phenyl-2,2′-bipyridyl, tBu₃terpy=4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridyl, and R=(a) adenine, (b) thymine, and (c) 2-amino-6-chloropurine) are stable in aqueous solutions for 48 hours at room temperature. The binding constants (K) for the platinum(II) complexes towards calf thymus DNA are in the order of 10⁵ dm³ mol⁻¹ as estimated by using UV/Vis absorption spectroscopy. Of the complexes examined, only complexes 1a, 1b, 1c are found to behave as intercalators. Both complexes 1a, 1b, 1c and 2a, 2b, 2c inhibit TopoII-induced relaxation of supercoiled DNA, while 2c is the most potent TopoII inhibitors among the tested compounds. Inhibition of DNA relaxation is detected at nanomolar concentrations of 2c. All of the platinum(II) complexes are cytotoxic to human cancer cells with IC₅₀ values of 0.5–13.7 μM, while they are less toxic against normal cells CCD-19 Lu.

Homoleptic d⁸-metal organothiolates and phenylselenolates [M(EC₆H₅)₂]_∞ (E=S, M=Pt 1, M=Pd 2, M=Ni 5; E=Se, M=Pt 3, M=Pd 4) were prepared as crystalline solids under solvothermal conditions. Their structures were solved using powder X-ray diffraction data. In each case, the EC₆H₅ (E=S, Se) ligand binds to two metal ions (M=Pt, Pd, and Ni) to form chain-like structures with planar (in 1) or zig-zag (in 2, 3, 4, 5) conformations. The [M(SR)₂]_∞ complexes (M=Pt, R=4-tert-butylphenyl 6; R=2-naphthyl 8; R=4-nitrophenyl 10 and M=Pd, R=4-tert-butylphenyl 7; R=2-naphthyl 9; R=4-nitrophenyl 11) were prepared under similar solvothermal conditions. Based on the XPS binding energies and elemental analyses, complexes 6, 7, 8, 9, 10, 11 have the same [M(SR)₂]_∞ formulation as 1 and 2. The cyclic complex [Pd₆(SCH₃)₁₂] 12 was prepared as a crystalline solid by solvothermal annealing treatment of the amorphous precipitate. A chain-like polymer structure is proposed for both [Pd(SC₁₂H₂₅)₂]_∞ 13 and [Pd(SC₁₆H₃₃)₂]_∞ 14; these polymeric chains self-assemble to give layer-like structures. Solid-state diffuse reflectance spectra reveal that the optical band gap E_g (eV) of complexes 1, 6, 8, 10 and of 2, 7, 9, 11 are in the range of 2.10–3.00 eV and 2.10–2.63 eV, respectively, and 5 has the lowest E_g value (1.72 eV). Heating solid samples of 4 and 13 under solvothermal conditions afforded phase-pure Pd₁₇Se₁₅ and PdS nanocrystals, respectively. Field-effect transistors fabricated with a drop-cast thin film made from Pd₁₇Se₁₅ nanocrystals prior treated with an ethanolic solution of 1-hexadecanethiol displayed ambipolar charge transporting properties with hole and electron mobility being 7×10⁻² cm² V⁻¹ s⁻¹ and 6×10⁻² cm² V⁻¹ s⁻¹, respectively.

Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 °C). Monodispersed (monodispersity: 11–15 %) metal nanoparticles were obtained with an average particle size of less than 5 nm (Ru: 1.8±0.2, Os: 1.6±0.2, Rh: 4.5±0.5, Ir: 2.0±0.3, Pd: 3.8±0.4, Pt: 1.9±0.2 nm). The size, monodispersity, and stability of the as-obtained metal nanoparticles were affected by the HEPES concentration, pH of the HEPES buffer solution, and reaction temperature. HEPES with two tertiary amines (piperazine groups) and terminal hydroxyl groups can act as a reductant and stabilizer. The HEPES molecules can bind to the surface of metal nanoparticles to prevent metal nanoparticles from aggregation. These platinum-group-metal nanoparticles could be deposited onto the surface of graphite, which catalyzed the aerobic oxidation of alcohols to aldehydes.

A series of platinum(II) complexes with tridentate ligands was synthesized and their interactions with G-quadruplex DNA within the c-myc gene promoter were evaluated. Complex 1, which has a flat planar 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy) scaffold, was found to stabilize the c-myc G-quadruplex structure in a cell-free system. An in silico G-quadruplex DNA model has been constructed for structure-based virtual screening to develop new Pt^II-based complexes with superior inhibitory activities. By using complex 1 as the initial structure for hit-to-lead optimization, bzimpy and related 2,6-bis(pyrazol-3-yl)pyridine (dPzPy) scaffolds containing amine side-chains emerge as the top candidates. Six of the top-scoring complexes were synthesized and their interactions with c-myc G-quadruplex DNA have been investigated. The results revealed that all of the complexes have the ability to stabilize the c-myc G-quadruplex. Complex 3 a ([Pt^IIL2R]⁺; L2=2,6-bis[1-(3-piperidinepropyl)-1H-enzo[d]imidazol-2-yl]pyridine, R=Cl) displayed the strongest inhibition in a cell-free system (IC₅₀=2.2 μM) and was 3.3-fold more potent than that of 1. Complexes 3 a and 4 a ([Pt^IIL3R]⁺; L3=2,6-bis[1-(3-morpholinopropyl)-1H-pyrazol-3-yl]pyridine, R=Cl) were found to effectively inhibit c-myc gene expression in human hepatocarcinoma cells with IC₅₀ values of ≈17 μM, whereas initial hit 1 displayed no significant effect on gene expression at concentrations up to 50 μM. Complexes 3 a and 4 a have a strong preference for G-quadruplex DNA over duplex DNA, as revealed by competition dialysis experiments and absorption titration; 3 a and 4 a bind G-quadruplex DNA with binding constants (K) of approximately 10⁶–10⁷ dm³ mol⁻¹, which are at least an order of magnitude higher than the K values for duplex DNA. NMR spectroscopic titration experiments and molecular modeling showed that 4 a binds c-myc G-quadruplex DNA through an external end-stacking mode at the 3′-terminal face of the G-quadruplex. Intriguingly, binding of c-myc G-quadruplex DNA by 3 b is accompanied by an increase of up to 38-fold in photoluminescence intensity at λ_max=622 nm.

Ruthenium porphyrins (particularly [Ru(2,6-Cl₂tpp)CO]; tpp=tetraphenylporphinato) and RuCl₃ can act as oxidation and/or Lewis acid catalysts for direct C-3 alkylation of indoles, giving the desired products in high yields (up to 82 % based on 60–95 % substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron-withdrawing or electron-donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N-arylindoles to 3-{[(N-aryl-N-alkyl)amino]methyl}indoles (yield: up to 82 %, conversion: up to 95 %) and the alkylation of N-alkyl or N-H indoles to 3-[p-(dialkylamino)benzyl]indoles (yield: up to 73 %, conversion: up to 92 %). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp³ CH bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N-arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three-component coupling reaction of the in situ generated formaldehyde with an N-alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium-labeling experiments are consistent with the alkylation of N-alkylindoles via pathway B. The relative reaction rates of [Ru(2,6-Cl₂tpp)CO]-catalyzed oxidative coupling reactions of 4-X-substituted N,N-dimethylanilines with N-phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants σ (R²=0.989), giving a ρ value of −1.09. This ρ value and the magnitudes of the intra- and intermolecular deuterium isotope effects (k_H/k_D) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4-X-substituted N,N-dimethylanilines. Ruthenium-catalyzed three-component reaction of N-alkyl/N-H indoles, paraformaldehyde, and anilines gave 3-[p-(dialkylamino)benzyl]indoles in up to 82 % yield (conversion: up to 95 %).

The syntheses, crystal structures, and detailed investigations of the photophysical properties of phosphorescent platinum(II) Schiff base complexes are presented. All of these complexes exhibit intense absorption bands with λ_max in the range 417–546 nm, which are assigned to states of metal-to-ligand charge-transfer (¹MLCT) ¹[Pt(5d)π*(Schiff base)] character mixed with ¹[lone pair(phenoxide)π*(imine)] charge-transfer character. The platinum(II) Schiff base complexes are thermally stable, with decomposition temperatures up to 495 °C, and show emission λ_max at 541–649 nm in acetonitrile, with emission quantum yields up to 0.27. Measurements of the emission decay times in the temperature range from 130 to 1.5 K give total zero-field splitting parameters of the emitting triplet state of 14–28 cm⁻¹. High-performance yellow to red organic light-emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A⁻¹ and a device lifetime up to 77 000 h at 500 cd m⁻².

The complexes [Pt(tBu₃tpy){CC(C₆H₄CC)_n−1R}]⁺ (n=1: R=alkyl and aryl (Ar); n=1–3: R=phenyl (Ph) or Ph-N(CH₃)₂-4; n=1 and 2, R=Ph-NH₂-4; tBu₃tpy=4,4’,4’’-tri-tert-butyl-2,2’:6’,2’’-terpyridine) and [Pt(Cl₃tpy)(CCR)]⁺ (R=tert-butyl (tBu), Ph, 9,9’-dibutylfluorene, 9,9’-dibutyl-7-dimethyl-amine-fluorene; Cl₃tpy=4,4’,4’’-trichloro-2,2’:6’,2’’-terpyridine) were prepared. The effects of substituent(s) on the terpyridine (tpy) and acetylide ligands and chain length of arylacetylide ligands on the absorption and emission spectra were examined. Resonance Raman (RR) spectra of [Pt(tBu₃tpy)(CCR)]⁺ (R=n-butyl, Ph, and C₆H₄-OCH₃-4) obtained in acetonitrile at 298 K reveal that the structural distortion of the CC bond in the electronic excited state obtained by 502.9 nm excitation is substantially larger than that obtained by 416 nm excitation. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations on [Pt(H₃tpy)(CCR)]⁺ (R= n-propyl (nPr), 2-pyridyl (Py)), [Pt(H₃tpy){CC(C₆H₄CC)_n−1Ph}]⁺ (n=1–3), and [Pt(H₃tpy){CC(C₆H₄CC)_n−1C₆H₄-N(CH₃)₂-4}]⁺/+H⁺ (n=1–3; H₃tpy=nonsubstituted terpyridine) at two different conformations were performed, namely, with the phenyl rings of the arylacetylide ligands coplanar (“cop”) with and perpendicular (“per”) to the H₃tpy ligand. Combining the experimental data and calculated results, the two lowest energy absorption peak maxima, λ₁ and λ₂, of [Pt(Y₃tpy)(CCR)]⁺ (Y=tBu or Cl, R=aryl) are attributed to ¹[π(CCR)π*(Y₃tpy)] in the “cop” conformation and mixed ¹[d_π(Pt)π*(Y₃tpy)]/¹[π(CCR)π*(Y₃tpy)] transitions in the “per” conformation. The lowest energy absorption peak λ₁ for [Pt(tBu₃tpy){CC(C₆H₄CC)_n−1C₆H₄-H-4}]⁺ (n=1–3) shows a redshift with increasing chain length. However, for [Pt(tBu₃tpy){CC(C6H4CC)_n−1C₆H₄-N(CH₃)₂-4}]⁺ (n=1–3), λ₁ shows a blueshift with increasing chain length n, but shows a redshift after the addition of acid. The emissions of [Pt(Y₃tpy)(CCR)]⁺ (Y=tBu or Cl) at 524–642 nm measured in dichloromethane at 298 K are assigned to the ³[π(CCAr)π*(Y₃tpy)] excited states and mixed ³[d_π(Pt)π*(Y₃tpy)]/³[π(CC)π*(Y₃tpy)] excited states for R=aryl and alkyl groups, respectively. [Pt(tBu₃tpy){CC(C₆H₄CC)_n−1C₆H₄-N(CH₃)₂-4}]⁺ (n=1 and 2) are nonemissive, and this is attributed to the small energy gap between the singlet ground state (S₀) and the lowest triplet excited state (T₁).

Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43–100 %) and product yields (66–99 %) (19 examples). Oxidation of N-substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO₃ solution gave the corresponding amides in good yields (83–93 %) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol “AuNPs/C+O₂” can be scaled to the gram scale, and 8.9 g (84 % isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed.

We herein report a theoretical analysis based on a density functional theory/time-dependent density functional theory (DFT/TDDFT) approach to understand the different phosphorescence efficiencies of a family of cyclometalated platinum(II) complexes: [Pt(NCN)Cl] (1; NCN=1,3-bis(2-pyridyl)phenyl⁻), [Pt(CNN)Cl] (2; CNN=6-phenyl-2,2′-bipyridyl⁻), [Pt(CNC)(CNPh)] (3; CNC=2,6-diphenylpyridyl²⁻), [Pt(R-CNN)Cl] (4; R-CNN=3-(6′-(2′′-naphthyl)-2′-pyridyl)isoquinolinyl⁻), and [Pt(R-CNC)(CNPh)] (5; R-CNC=2,6-bis(2′-naphthyl)pyridyl²⁻). By considering both the spin–orbit coupling (SOC) and the electronic structures of these complexes at their respective optimized singlet ground (S₀) and first triplet () excited states, we were able to rationalize the experimental findings that 1) 1 is a strong emitter while its isomer 2 is only weakly emissive in CH₂Cl₂ solution at room temperature; 2) although the cyclometalated ligand of 3 has a higher ligand-field strength than that of 1, 3 is nonemissive in CH₂Cl₂ solution at 298 K; and 3) extension of π conjugation at the lateral aryl rings of the cyclometalated ligands of 2 and 3 to give 4 and 5, respectively, leads to increased emission quantum yields under the same conditions. We found that Jahn–Teller and pseudo-Jahn–Teller effects are operative in complexes 2 and 3, respectively, on going from the optimized S₀ ground state to the optimized excited state, and thus lead to large excited-state structural distortions and hence fast nonradiative decay. Furthermore, a strong-field ligand may push the two different occupied d orbitals so far apart that the SOC effect is small and the radiative decay rate is slow. This work is an example of electronic-structure-driven tuning of the phosphorescence efficiency, and the DFT/TDDFT approach is demonstrated to be a versatile tool for the design of phosphorescent materials with target characteristics.

The complexes [Au₃(dcmp)₂][X]₃ {dcmp=bis(dicyclohexylphosphinomethyl)cyclohexylphosphine; X=Cl⁻ (1), ClO₄⁻ (2), OTf⁻ (3), PF₆⁻ (4), SCN⁻(5)}, [Ag₃(dcmp)₂][ClO₄]₃ (6), and [Ag₃(dcmp)₂Cl₂][ClO₄] (7) were prepared and their structures were determined by X-ray crystallography. Complexes 2–4 display a high-energy emission band with λ_max at 442–452 nm, whereas 1 and 5 display a low-energy emission with λ_max at 558–634 nm in both solid state and in dichloromethane at 298 K. The former is assigned to the ³[5dσ*6pσ] excited state of [Au₃(dcmp)₂]³⁺, whereas the latter is attributed to an exciplex formed between the ³[5dσ*6pσ] excited state of [Au₃(dcmp)₂]³⁺ and the counterions. In solid state, complex [Ag₃(dcmp)₂][ClO₄]₃ (6) displays an intense emission band at 375 nm with a Stokes shift of ≈7200 cm⁻¹ from the ¹[4dσ*5pσ] absorption band at 295 nm. The 375 nm emission band is assigned to the emission directly from the ³[4dσ^*5pσ] excited state of 6. Density functional theory (DFT) calculations revealed that the absorption and emission energies are inversely proportional to the number of metal ions (n) in polynuclear Au^I and Ag^I linear chain complexes without close metal⋅⋅⋅anion contacts. The emission energies are extrapolated to be 715 and 446 nm for the infinite linear Au^I and Ag^I chains, respectively, at metal⋅⋅⋅metal distances of about 2.93–3.02 Å. A QM/MM calculation on the model [Au₃(dcmp)₂Cl₂]⁺ system, with Au⋅⋅⋅Cl contacts of 2.90–3.10 Å, gave optimized Au⋅⋅⋅Au distances of 2.99–3.11 Å in its lowest triplet excited state and the emission energies were calculated to be at approximately 600–690 nm, which are assigned to a three-coordinate Au^I site with its spectroscopic properties affected by Au^I⋅⋅⋅Au^I interactions.

The interactions of a series of platinum(II) Schiff base complexes with c-myc G-quadruplex DNA were studied. Complex [PtL^1a] (1 a; H₂L^1a=N,N′-bis(salicylidene)-4,5-methoxy-1,2-phenylenediamine) can moderately inhibit c-myc gene promoter activity in a cell-free system through stabilizing the G-quadruplex structure and can inhibit c-myc oncogene expression in cultured cells. The interaction between 1 a and G-quadruplex DNA has been examined by ¹H NMR spectroscopy. By using computer-aided structure-based drug design for hit-to-lead optimization, an in silico G-quadruplex DNA model has been constructed for docking-based virtual screening to develop new platinum(II) Schiff base complexes with improved inhibitory activities. Complex [PtL³] (3; H₂L³=N,N′-bis{4-[1-(2-propylpiperidine)oxy]salicylidene}-4,5-methoxy-1,2-phenylenediamine) has been identified with a top score in the virtual screening. This complex was subsequently prepared and experimentally tested in vitro for its ability to stabilize or induce the formation of the c-myc G-quadruplex. The inhibitory activity of 3 (IC₅₀=4.4 μM) is tenfold more than that of 1 a. The interaction between 1 a or 3 with c-myc G-quadruplex DNA has been examined by absorption titration, emission titration, molecular modeling, and NMR titration experiments, thus revealing that both 1 a and 3 bind c-myc G-quadruplex DNA through an external end-stacking mode at the 3’ terminal face of the G-quadruplex. Such binding of G-quadruplex DNA with 3 is accompanied by up to an eightfold increase in the intensity of photoluminescence at λ_max=652 nm. Complex 3 also effectively down-regulated the expression of c-myc in human hepatocarcinoma cells.

Gold(I) and copper(I) phosphane complexes containing the 4-nitrophenylthiolate ligand, namely [(PCy₃)Au(SC₆H₄NO₂-4)] (1) (PCy₃ = tricyclohexylphosphane), [Au₂(μ-dcpm)(SC₆H₄NO₂-4)₂] (2) [dcpm = bis(dicyclohexylphosphanyl)methane], [Au₂(μ-dppm)(SC₆H₄NO₂-4)₂] (3) [dppm = bis(diphenylphosphanyl)methane], and [(μ₂-SC₆H₄NO₂-4)₂(μ₃-SC₆H₄NO₂-4)₂(CuPPh₃)₄] (4), were prepared and characterized by X-ray crystal analysis. All of these complexes show an intense absorption band with λ_max at 396–409 nm attributed to the intraligand (IL) π(S)π*(C₆H₄NO₂-4) charge-transfer transition. The assignment is supported by the results of DFT and TDDFT calculations on the model complexes [PH₃Au(SC₆H₄NO₂-4)] and [(μ₂-SC₆H₄NO₂-4)₂(μ₃-SC₆H₄NO₂-4)₂(CuPH₃)₄]. The emissions of solid samples and glassy solutions (methanol/ethanol, 1:4, v/v) of 1–4 at 77 K are assigned to the [π(S)π*(C₆H₄NO₂-4)] charge-transfer excited state. Metallophilic interactions are not observed in both solid state and solutions of complexes 1–3. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A series of binuclear organoplatinum(II) complexes, [(tBu₃tpy)Pt(CC1,2-C₆H₄)_nCCPt(tBu₃tpy)][ClO₄]₂ (1–7, n=1, 2, 3, 4, 5, 6, 8; tBu₃tpy=4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine) with foldable oligo(ortho-phenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 3⋅2.5 CH₃OH, 5⋅CH₃CN, and 6⋅4 CH₃CN, each of the bridging ortho-phenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40 %, the emission of complexes 3–7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho-phenyleneethynylene linkers in acetonitrile/water mixtures is postulated.

Density functional theory (DFT) calculations on trans-dioxo metal complexes containing saturated amine ligands, trans-[M(O)₂(NH₃)₂(NMeH₂)₂]²⁺ (M=Fe, Ru, Os), were performed with different types of density functionals (DFs): 1) pure generalized gradient approximations (pure GGAs): PW91, BP86, and OLYP; 2) meta-GGAs: VSXC and HCTH407; and 3) hybrid DFs: B3LYP and PBE1PBE. With pure GGAs and meta-GGAs, a singlet d² ground state for trans-[Fe(O)₂(NH₃)₂(NMeH₂)₂]²⁺ was obtained, but a quintet ground state was predicted by the hybrid DFs B3LYP and PBE1PBE. The lowest transition energies in water were calculated to be at λ≈509 and 515 nm in the respective ground-state geometries from PW91 and B3LYP calculations. The nature of this transition is dependent on the DFs used: a ligand-to-metal charge-transfer (LMCT) transition with PW91, but a π(FeO)π*(FeO) transition with B3LYP, in which π and π* are the bonding and antibonding combinations between the d_π(Fe) and p_π(O²⁻) orbitals. The Fe^VI/V reduction potential of trans-[Fe(O)₂(NH₃)₂(NMeH₂)₂]²⁺ was estimated to be +1.30 V versus NHE based on PW91 results. The [Fe(qpy)(O)₂]ⁿ⁺ (qpy=2,2′:6′,2′′:6′′,2′′′:6′′′,2′′′′-quinquepyridine; n=1 and 2) ions, tentatively assigned to dioxo iron(V) and dioxo iron(VI), respectively, were detected in the gas phase by high-resolution ESI-MS spectroscopy.

Polymeric homoleptic copper(I) arylthiolates [Cu(p-SC₆H₄-X)]_∞ (X=CH₃ (1), H (2), CH₃O (3), tBu (4), CF₃ (5), NO₂ (6), and COOH (7)) have been prepared as insoluble crystalline solids in good yields (75–95 %). Structure determinations by powder X-ray diffraction analysis have revealed that 1–3 and 6 form polymers of infinite chain length, with the copper atoms bridged by arylthiolate ligands. Weak intra-chain π⋅⋅⋅π stacking interactions are present in 1–3, as evidenced by the distances (3.210 Å in 1, 3.016 Å in 2, 3.401 Å in 3) between the mean planes of neighboring phenyl rings. In the structure of 6, the intra-chain π⋅⋅⋅π interactions (d=3.711 Å) are insignificant and the chain polymers are associated through weak, non-covalent CH⋅⋅⋅O hydrogen-bonding interactions (d=2.586 Å). Samples of 1–7 in their polycrystalline forms proved to be thermally stable at 200–300 °C; their respective decomposition temperatures are around 100 °C higher than that of the aliphatic analogue [Cu(SCH₃)]_∞. Data from in situ variable-temperature X-ray diffractometry measurements indicated that the structures of both 1 and 7 are thermally more robust than that of [Cu(SCH₃)]_∞. TEM analysis revealed that the solid samples of 1–5 and [Cu(SCH₃)]_∞ contained homogeneously dispersed crystalline nanorods with widths of 20–250 nm, whereas smaller plate-like nanocrystals were found for 6 and 7. SAED data showed that the chain polymers of 1–3 and [Cu(SCH₃)]_∞ similarly extend along the long axes of their nanorods. The nanorods of 1–5 and [Cu(SCH₃)]_∞ have been found to exhibit p-type field-effect transistor behavior, with charge mobility (μ) values of 10⁻²–10⁻⁵ cm² V⁻¹ s⁻¹. Polycrystalline solid samples of 6 and 7 each showed a low charge mobility (<10⁻⁶ cm² V⁻¹ s⁻¹). The charge mobility values of field-effect transistors made from crystalline nanorods of 1–3 and [Cu(SCH₃)]_∞ could be correlated with their unique chain-like copper–sulfur networks, with the para-substituent of the arylthiolate ligand influencing the charge-transport properties.

Metal octaethylporphyrin M(OEP) (M=Ni, Cu, Zn, Pd, Ag, and Pt) nanowires are fabricated by a simple solution-phase precipitative method. By controlling the composition of solvent mixtures, the diameters and lengths of the nanowires can be varied from 20 to 70 nm and 0.4 to 10 μm, respectively. The Ag(OEP) nanowires have lengths up to 10 μm and diameters of 20–70 nm. For the M(OEP) nanowires, the growth orientation and packing of M(OEP) molecules are examined by powder XRD and SAED measurements, revealing that these M(OEP) nanowires are formed by the self-assembly of M(OEP) molecules through intermolecular π⋅⋅⋅π interactions along the π⋅⋅⋅π stacking axis, and the M²⁺ ion plays a key role in the nanowire formation. Using the bottom contact field effect transistor structure and a simple drop-cast method, a single-crystal M(OEP) nanowires-based field effect transistor can be readily prepared with prominent hole transporting behaviour and charge-carrier mobility up to 10⁻³–10⁻² cm² V⁻¹ s⁻¹ for holes, which are 10 times higher than that of vacuum-deposited M(OEP) organic thin-film transistors (OTFTs).

Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl₂(C₆H₅CO₂Et)]₂ with polystyrene in open air. They effectively catalyze intra- and intermolecular carbenoid insertion into CH and NH bonds, alkene cyclopropanation, and ammonium ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl₂(p-cymene)]₂ and [Ru(Por)CO] for catalytic intermolecular carbenoid CH bond insertion into saturated alkanes. By using α-diazoacetamide as a substrate for intramolecular carbenoid CH insertion, the supported ruthenium catalyst can be recovered and reused for ten successive iterations without significant loss of activity.

Organic field-effect transistors incorporating planar π-conjugated metal-free macrocycles and their metal derivatives are fabricated by vacuum deposition. The crystal structures of [H₂(OX)] (H₂OX=etioporphyrin-I), [Cu(OX)], [Pt(OX)], and [Pt(TBP)] (H₂TBP=tetra-(n-butyl)porphyrin) as determined by single crystal X-ray diffraction (XRD), reveal the absence of occluded solvent molecules. The field-effect transistors (FETs) made from thin films of all these metal-free macrocycles and their metal derivatives show a p-type semiconductor behavior with a charge mobility (μ) ranging from 10⁻⁶ to 10⁻¹ cm² V⁻¹ s⁻¹. Annealing the as-deposited Pt(OX) film leads to the formation of a polycrystalline film that exhibits excellent overall charge transport properties with a charge mobility of up to 3.2×10⁻¹ cm² V⁻¹ s⁻¹, which is the best value reported for a metalloporphyrin. Compared with their metal derivatives, the field-effect transistors made from thin films of metal-free macrocycles (except tetra-(n-propyl)porphycene) have significantly lower μ values (3.0×10⁻⁶–3.7×10⁻⁵ cm² V⁻¹ s⁻¹).

A dicationic platinum(II) terpyridyl complex, [(tBu₃tpy)Pt(OXD)Pt(tBu₃tpy)](PF₆)₂ (tBu₃tpy=4,4′,4“-tri-tert-butyl-2,2′:6′,2”-terpyridyl, OXD=2,5-bis(4-ethynylphenyl)[1,3,4]oxadiazole) formed phosphorescent organogels in acetonitrile or in a mixture of acetonitrile and alcohol. The structure and properties of these emissive gels were analyzed by polarizing optical and confocal laser scanning microscopy, and by variable-temperature ¹H NMR, UV/Vis, and emission spectroscopy. Dry gels were studied by scanning electron microscopy, powder X-ray diffraction (PXRD), and small-angle X-ray scattering (SAXS). SEM images of the dry gel revealed a network of interwoven nanofibers (diameter 12–60 nm, length>5 μm). Intermolecular π–π interactions between the [(tBu₃tpy)PtC≡C] moieties could be deduced from the variable ¹H NMR spectra. The PXRD and SAXS data showed that the assembly of the gelator could be represented by a rectangular 2D lattice of 68 Å × 14 Å. The ability of the complex to gelate a number of organic solvents is most likely due to intermolecular π–π interactions between the [(tBu₃tpy)PtC≡C] moieties.

A simple and green method that uses [Ru(Me₃tacn)Cl₃] (1; Me₃tacn=N,N′,N′′-trimethyl-1,4,7-triazacyclononane) as catalyst, aqueous H₂O₂ as the terminal oxidant, and Al₂O₃ and NaCl as additives is effective in the cis-dihydroxylation of alkenes in aqueous tert-butanol. Unfunctionalized alkenes, including cycloalkenes, aliphatic alkenes, and styrenes (14 examples) were selectively oxidized to their corresponding cis-diols in good to excellent yield (70–96 %) based on substrate conversions of up to 100 %. The preparation of cis-1,2-cycloheptanediol (119 g, 91 % yield) and cis-1,2-cyclooctanediol (128 g, 92 % yield) from cycloheptene and cyclooctene, respectively, on the 1-mol scale can be achieved by scaling up the reaction without modification. Results from Hammett correlation studies on the competitive oxidation of para-substituted styrenes (ρ=−0.97, R=0.988) and the detection of the cycloadduct [(Me₃tacn)ClRuHO₂(C₈H₁₄)]⁺ by ESI-MS for the 1-catalyzed oxidation of cyclooctene to cis-1,2-cyclooctanediol are similar to those of the stoichiometric oxidation of alkenes by cis-[(Me₃tacn)(CF₃CO₂)Ru^VIO₂]⁺ through [3+2] cycloaddition (W.-P. Yip, W.-Y. Yu, N. Zhu, C.-M. Che, J. Am. Chem. Soc.2005, 127, 14239).