A highly stable porphyrin-based porous organic polymer PPOP-1(Fe) with a three-dimensional diamond structure was synthesized via imine condensation of a tetrahedral aldehyde and a linear porphyrin diamine. PPOP-1(Fe) exhibits excellent catalytic activity as a biomimetic catalyst, because the heme-like porphyrin active centers in PPOP-1(Fe) are exposed toward the open channels, thus accelerating the catalytic oxidation reactions.

AgNWs@SCO nanocomposites were constructed by in situ growing spin-crossover (SCO) nanoparticles on silver nanowires (AgNWs). The obtained AgNWs@[Fe(Htrz)2(trz)](BF4) (AgNWs@SCO-1) and AgNWs@Fe(pz)[Pt(CN)4] (AgNWs@SCO-2) nanomaterials were characterized by FT-IR, PXRD, Raman spectroscopy, SEM and TEM. SEM images show that SCO NPs grow on the surface of the AgNWs, and their size and shape can be tuned by controlling the amount of added iron(II) salt. The magnetic measurements exhibit hysteresis loops with 45 K (Tc↑ = 385 K, Tc↓ = 340 K) for SCO-1 and 31 K (Tc↑ = 290 K, Tc↓ = 259 K) for SCO-2. It is interesting that both AgNWs@SCO nanocomposites retain spin-crossover behaviour with hysteresis loops with 50 K (Tc↑ = 395 K and Tc↓ = 345 K) for AgNWs@SCO-1 and 34 K (Tc↑ = 289 K and Tc↓ = 255 K) for AgNWs@SCO-2. The hot pressing method is used to transfer AgNWs@SCO nanocomposites to flexible PET substrates for a four-probe conductivity test. The conductivities of AgNWs@SCO-1 and AgNWs@SCO-2 are consistent with that of the individual AgNWs over the 100–350 K range, indicating that AgNWs@SCO nanocomposites exhibit good conductivity. The combination of both spin-crossover properties and conductive properties in AgNWs@SCO materials provides a great prospect for their application in devices.

Two iron(II) molecular isomers, namely face-Λ-[Fe(L1)3](ClO4)2 (1a) (L1 = R-1-phenyl-N-((1-hexyl-5-methyl-1H-imidazol-2-ylmethylene)ethanamine)) and face-Λ-[Fe(L2)3](ClO4)2 (1b) (L2 = R-1-phenyl-N-(1-hexyl-4-methyl-1H-imidazol-2-ylmethylene)ethanamine), are obtained via a well-designed strategy based on the tautomerization of the 4(5)-methylimidazole group. Structural investigations reveal that the two isomers are extremely similar with only differences in the methyl group position of the ligands. The iron(II) center is surrounded by three bidentate imidazole Schiff-base ligands in the face-Λ conformation, which affords a distorted [FeN6] octahedral coordination sphere. The average Fe–N bond length of 1a (1.971 Å) is shorter than that of 1b (2.185 Å). Spectroscopy analyses, X-ray crystal structures and magnetic investigations show that 1a is in the low-spin state at room temperature due to the strong ligand field imparted by the electron-donating methyl groups at the 5-position on the imidazole moieties and undergoes a partial spin transition with an estimated T1/2 = 390 K. In contrast, 1b is stabilized in the high-spin state because of the strong steric hindrance when the three methyl “legs” are changed from the 5-position to the 4-position on the imidazole moieties. In addition, a new complex, 2, without methyl groups attached to the imidazole rings is introduced and characterized to further corroborate the steric influence on the spin state. Complex 2 exhibits a gradual spin-crossover behaviour with T1/2 = 258 K. Moreover, the diverse spin states of these complexes are computationally studied using the DFT method. The results of the calculations are consistent with the experiments, which prove that the competition of the electronic effect and steric crowding influence the spin states.

Two solvent-free polymorphs of a chiral iron(II) complex have been obtained, and their polymorphism dependent spin-crossover and ferroelectric properties have been demonstrated. Polymorph I shows a gradual spin-crossover behavior, whereas polymorph II remains in a high-spin state but shows a typical ferroelectric feature.

A metalloporphyrin-based porous organic polymer, Mn-PPOP-1, was constructed in high yield via the ketoenamine condensation of robust porphyrin tetraamines (TBPP) with 1,3,5-triformylphloroglucinol. The stable keto-enamine form in the synthesized polymer was unambiguously confirmed by 13C CP-MAS solid state NMR. Noticeably, besides the high thermal and chemical stability, this material contains both micropores and mesopores, which are favorable for mass transfer in the catalytic application. Mn-PPOP-1 exhibits significantly high catalytic oxidation of olefins and arylalkanes at room temperature. The catalytic activity and stability of Mn-PPOP-1 are apparently superior to those of the homogeneous manganese porphyrins. These results indicate that the metalloporphyrin-based porous organic polymer is a promising candidate for efficient heterogeneous catalysts.

The first SCO@SCO core–shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core–shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials.

Four pairs of enantiomers of water-stable tetrahedral metal–organic cages [Ni4L6]8+ were facilely synthesized. They efficiently stabilized antiparallel G-quadruplex DNA with moderate enantioselectivity, and displayed promising cytotoxicity against the human cancer cell lines HCT116, HepG2 and MCF-7. These results provide a new insight into the rational design of chiral G-quadruplex-based anticancer agents.

An effective single crystal to single crystal transformation from a tetrahedral Ni cage to an FeNi cage was demonstrated. The iron(II) centers of the FeNi cage can be induced to display spin crossover behaviors with an increasing amount of Fe(II) ions. The SCSC metal-center exchange provides a powerful approach to modify solid magnetic properties.

Through multi-component self-assembly of chiral phenylethylamine, 1-alkyl-2-imidazolecarboxaldehyde and iron(II) ions, two couples of enantiomeric iron(II) complexes 4R, 4S, 5R and 5S with the formula of fac-Λ or Δ-[Fe(L)3]2+(L = R or S-1-phenyl-N-(1-alkyl-1H-imidazol-2-ylmethylene)ethanamine) have been designed and synthesized as building blocks. Further binary cocrystallization of the prefabricated enantiomers enabled us to construct spin crossover co-enantiomers 4R5R and 4S5S, racemates 4RS and 5RS, and co-racemate 4RS5RS. Compared with 4R in a high spin state and 5R with spin crossover at 291 K, the co-enantiomers 4R5R exhibited gradual spin crossover at a higher temperature of 301 K, and the racemic alloys showed hysteresis loops induced by desolvation above room temperature. It was demonstrated that molecular chirality could be used effectively for stereochemical engineering of spin crossover materials. In addition, crystal packing, intramolecular π–π stacking, intermolecular C–H⋯π interactions and solvent effects were elucidated to be responsible for the distinct spin crossover properties. This collective structural and magnetic study not only enriched the spin crossover library, but also provided a full comparison of optically pure, homochiral, and racemic materials with similar molecular structures.

Inorganic ion exchangers in hydrogen forms, H0.36La0.55TiO3 (HLTO), H4Ti5O12 (HTO12) and H2Ti3O7 (HTO7) have been prepared by acid treatment of Li0.36La0.55TiO3, Li4Ti5O12 and Li2Ti3O7, respectively, which were synthesized by the solid-state reaction method. The selectivity of metal ions, Li+ ion exchange property and lithium isotopes separation property were investigated. The three ion exchangers were isotopically 6Li-specific, and the maximum single-stage separation factors of 6Li/7Li, were 1.042, 1.037 and 1.035 for HLTO, HTO12, and HTO7, respectively. The structures of HLTO, HTO12 and HTO7 were stable and they can be regenerated and recyclable in three cycles.

A new class of chiral tetrahedral iron(II) cages were prepared from subcomponent self-assembly with high diastereoselectivity. The cages can be interconverted through imine exchange. The chiral cages displayed a spin transition close to room temperature, and the transition temperatures were affected by the substituent and uncoordinated solvents.

A homochiral complex 1·MeCN was synthesized by the multicomponent self-assembly of (R)-phenylethylamine, 1-methyl-2-imidazolecarboxaldehyde and iron(II) ions in acetonitrile solution. X-ray crystallography analysis revealed that complex 1·MeCN crystallized in the chiral space group P21. The octahedral coordination mononuclear [FeL3]2+ cations are stacked into a left-handed double helix supramolecular structure along the a axis with uncoordinated acetonitrile molecules filling the helical channel. Interestingly, when 1·MeCN redissolved in racemic lactonitrile (LN) or methylglutaronitrile (MGN), the [FeL3]2+ cations can recognize one enantiomeric alkyl nitrile by forming 1·1/3(R)-LN or 1·1/3(S)-MGN crystals. 1·1/3(R)-LN and 1·1/3(S)-MGN crystallized in the P212121 space group, and the [FeL3]2+ cations are stacked in a triple helix mode with the enantiomeric alkyl nitrile captured in the helical channel. Magnetic measurement indicated that 1·MeCN displayed spin-crossover at 355 K, while the transition temperature became 220 K after desolvation. However, 1·1/3(R)-LN and 1·1/3(S)-MGN exhibited incomplete and reversible spin-crossover behaviors at about 363 K. The results demonstrated that the mononuclear iron(II) complex could be used as a host for racemic alkyl nitrile separation, and the spin-crossover property was influenced by the process of chiral recognition.

•Spin-crossover iron(II) enantiomeric complexes 1-4 were synthesized.•Chiral polymers 5-8 were synthesized by grafting 1-4 to the merrifield’s peptide resin.•The spin-crossover behavior presented in monomer complexes 1-4 was vanished in polymers 5-8.Using chiral imidazole Schiff-base as ligands, two couples of mononuclear iron(II) enantiomeric complexes fac-Λ-[Fe(R-L)3](ClO4)2·H2O (1), fac-Δ-[Fe(S-L)3](ClO4)2·H2O (2), fac-Λ-[Fe(R-L)3](BF4)2·H2O (3), fac-Δ-[Fe(S-L)3](BF4)2·H2O (4) (L = 1-(2-naphthyl)-N-((1-methyl-imidazol-2-yl)methylene)ethanamine) have been successfully synthesized and characterized. The CD spectra of 1 and 2, 3 and 4, were basically mirror images confirming their enantiomers. X-ray crystallography revealed that complexes 1–4 all crystallized in the chiral space group P213 with the iron(II) center surrounded by three bidentate ligands. Magnetic measurements revealed incomplete spin transition for 1, and gradual spin crossover (T1/2 = 150 K) for 3. However, the spin-crossover behaviors were vanished after grafting 1–4 to the Merrifield's peptide resin, and the iron(II) centers in the resin remained in a high-spin state in the temperature range of 2–300 K.Two couples of mononuclear spin-crossover iron(II) enantiomeric complexes 1–4 and their Merrifield's peptide resin-supported chiral compounds 5–8 have been successfully synthesized. Magnetic measurements revealed that monomer complexes 1–4 displayed obvious spin-crossover properties, while the spin-crossover behavior presented in monomer complexes 1–4 was vanished after it was grafted to the resin.

•Four homochiral spin-crossover iron(II) imidazole Schiff-base complexes have been successfully synthesized.•1–4 displayed obviously spin-crossover behavior at 257, 375, 137 and 282 K, respectively.•The different SCO behaviors may result from substitution effect, packing mode, and intermolecular interactions.Four novel homochiral mononuclear spin-crossover iron(II) complexes 1–4 have been successfully synthesized by subcomponent self-assembly of Fe(ClO4)2, 1-substituted imidazole-2-carboxaldehyde and optical phenylethylamine derivatives. X-ray crystallography revealed that the iron(II) center in 1–4 assumed an octahedral coordination environment with 6 N donor atoms from three unsymmetrical bidentate chiral Schiff-base ligands. [Fe(Ln)3]2 + components were chiral with either Λ or Δ configuration due to the screw coordination arrangement of the chiral ligands around Fe(II) center. Circular dichromism spectra confirmed the presence of non-racemic chiral metal centers in solution for 1–4. Magnetic measurements revealed that 1–4 displayed obviously spin-crossover behavior at 257, 375, 137 and 282 K, respectively. The different SCO behaviors of 1–4 may result from substitution effect, packing mode, and intermolecular interactions.Four novel homochiral mononuclear spin-crossover iron(II) complexes 1–4 have been successfully synthesized by subcomponent self-assembly. [Fe(Ln)3]2 + components in 1–4 were chiral with either Λ or Δ configuration due to the screw coordination arrangement of the chiral ligands around Fe(II) center. 1–4 displayed obviously spin-crossover behavior at 257, 375, 137 and 282 K, respectively.

A facile way to fabricate spin crossover-graphene nanocomposites has been developed, and [Fe(Htrz)2(trz)](BF4)–graphene (SCO-G) nanocomposites have been successfully synthesized and characterized. SEM and TEM demonstrated that [Fe(Htrz)2(trz)](BF4) nanoparticles (ca. 50 nm) were distributed uniformly onto the surface of the graphene. Interestingly, graphene as a substrate produced an effect on the spin crossover properties of [Fe(Htrz)2(trz)](BF4) nanoparticles.

We report here an effective synthetic route to gold coated spin-crossover core–shell nanocomposites (SCO@SiO2@Au) in which [Fe(Htrz)2(trz)](BF4)@SiO2 (SCO@SiO2) served as a support to the Au nanoparticles. The obtained core–shell nanocomposites were studied using numerous characterization techniques to define the structure, morphology, composition and especially the spin-crossover properties. The transmission electron micrographs illustrated that Au nanoparticles with an average diameter around 2.5 nm were decorated uniformly on the surface of SCO@SiO2. X-ray photoelectron spectroscopy measurements further confirmed the successful incorporation of gold nanoparticles on spin-crossover core. The Raman spectrum indicated that the plasmonic Au nanoparticles caused an efficient photo-thermal heating in the SCO@SiO2@Au nanocomposites, leading to a ∼100 times reduction of laser energy needed for spin state switching compared with SCO@SiO2. The magnetic study demonstrated that the embedded Au nanoparticles not only influenced the spin transition temperatures but also changed the widths of hysteresis loops. SCO@SiO2@Au nanocomposites may be applied to various areas where the fascinating spin-crossover core and the functional gold shell can be beneficial.

DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7] · 2CH3OH · 5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2] · 2CH3OH · 4H2O (M-La and P-La, L = 2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery.Effective DNA condensation was induced by a pair of heptameric lanthanum helical supramolecular enantiomers M-La and P-La. The enantiomers showed discrimination in DNA condensing with apparent retardation of DNA gel electrophoresis band. The DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state.

•Homochiral iron(II) complexes based on imidazole Schiff-base ligands were reported.•R-L ligand induces the fac-Λ isomer, while S-L ligand induces the fac-Δ isomer.•Iron(II) enantiomeric complexes display obviously spin-crossover behavior.A pair of mononuclear iron(II) enantiomeric complexes: fac-Λ-[Fe(R-L)3](BF4)2·MeCN (1) and fac-Δ-[Fe(S-L)3](BF4)2·MeCN (2) [L = 1-phenyl-N-(1-methyl-imidazol-2-ylmethylene)ethanamine] have been synthesized and characterized. X-ray crystallography reveals that iron(II) center is surrounded by three bidentate ligands defining a pseudooctahedral [FeN6] coordination environment. R-L ligand induces the fac-Λ isomer, while S-L ligand induces the fac-Δ isomer. Magnetic measurements reveal that both of them display obviously spin-crossover behavior at 365 K. After desolvation, they exhibit a reversible spin transition with a small hysteresis loop of ca. 3 K appearing at about T1/2↑ = 222 K and T1/2↓ = 219 K.Two new homochiral iron(II) enantiomeric complexes have been synthesized and characterized. Magnetic measurements reveal that both of them display obviously spin-crossover behavior at 365 K. After desolvation, they exhibit a reversible spin transition with a small hysteresis loop appearing at about T1/2↑ = 222 K and T1/2↓ = 219 K.

A fascinating polythreaded coordination network formed by 1D crankshaft shaped chains threading into a 2D undulated sheet in a one-over/one-under interweaving fashion was reported, in which the 2D layer exhibits an unusual polyknotted entanglement containing triple-stranded molecular braids.

A new three-dimensional heterometallic MnIICuII azide-bridged coordination polymer, [Mn2Cu(N3)6(en)2]n (1), was synthesized by assembling MnII, CuII, azide, and ethylenediamine in solution condition. The 3D structure of 1 can be described as end-on (EO) azide-bridged Mn2Cu trinuclear units linked by end-to-end (EE) azide bridges. Magnetic analysis of 1 indicates that the EO- and EE-azide bridges mediate the ferromagnetic and antiferromagnetic exchange interactions, respectively, with the antiferromagnetic coupling dominating the magnetic properties.A new three-dimensional heterometallic MnIICuII azide-bridged coordination polymer, [Mn2Cu(N3)6(en)2]n (1) has been synthesized and structurally characterized. Magnetic measurements indicate antiferromagnetic coupling dominating the magnetic properties of 1.Highlights► Three-dimensional heterometallic MnIICuII azide-bridged coordination polymer. ► Mn2Cu trinuclear units linked by end-to-end azide bridges. ► Antiferromagnetic coupling dominating the magnetic properties.

The reactions of copper(II) ions with azido ligands in the presence of different chelating amine ligands gave three one dimensional copper-azido molecular tapes, [Cu2(N-Pren)(N3)4]n (1), [Cu2(N-Buen)(N3)4]n (2) and [Cu3(tren)(N3)6]n (3) [N-Pren = N-propylethylenediamine; N-Buen = N-butylethylenediamine; tren = tris(2-aminoethyl)amine]. Complexes 1 and 2 are composed of 1D coordination chains based on the step-like tetranuclear copper(II) clusters which feature three types of azido bridging modes (μ-1,1, μ-1,3 and μ-1,1,1). Complex 3 is a novel 1D molecular tape featuring zigzag hexanuclear copper-azido subunits with only end-on azido bridges. Magnetic studies show ferromagnetic coupling in 1 and 2, and antiferromagnetic coupling in 3. The magnetic data for 1 and 2 were fitted with a tetranuclear copper theoretical model.

A new polyiron complex [Fe17(OH)7O11(O2CPh)20(N3)2]·4H2O·10MeCN (1), with compact [Fe17(OH)7O11] core encapsulated by twenty benzoate anions and two end-on (EO) azido ligands has been synthesized and structurally characterized. Intramolecular antiferromagnetic couplings are observed for 1 and it has S = 35/2 ground state which was confirmed by magnetic measurements and Mössbauer spectra.A novel polyiron cluster [Fe17(OH)7O11(O2CPh)20(N3)2]·4H2O·10MeCN (1) has been synthesized and structurally characterized. Magnetic measurements and Mössbauer spectra studies indicate that cluster 1 has S = 35/2 ground state.Research highlights► Fe17 cluster contains both oxo and end-on azido bridges. ► Seventeen iron(III) ions are encapsulated by twenty benzoate and two azido ligands. ► Fe17 cluster has large ground spin state of S = 35/2.

Two solvent-free polymorphs of a chiral iron(II) complex have been obtained, and their polymorphism dependent spin-crossover and ferroelectric properties have been demonstrated. Polymorph I shows a gradual spin-crossover behavior, whereas polymorph II remains in a high-spin state but shows a typical ferroelectric feature.

Two iron(II) molecular isomers, namely face-Λ-[Fe(L1)3](ClO4)2 (1a) (L1 = R-1-phenyl-N-((1-hexyl-5-methyl-1H-imidazol-2-ylmethylene)ethanamine)) and face-Λ-[Fe(L2)3](ClO4)2 (1b) (L2 = R-1-phenyl-N-(1-hexyl-4-methyl-1H-imidazol-2-ylmethylene)ethanamine), are obtained via a well-designed strategy based on the tautomerization of the 4(5)-methylimidazole group. Structural investigations reveal that the two isomers are extremely similar with only differences in the methyl group position of the ligands. The iron(II) center is surrounded by three bidentate imidazole Schiff-base ligands in the face-Λ conformation, which affords a distorted [FeN6] octahedral coordination sphere. The average Fe–N bond length of 1a (1.971 Å) is shorter than that of 1b (2.185 Å). Spectroscopy analyses, X-ray crystal structures and magnetic investigations show that 1a is in the low-spin state at room temperature due to the strong ligand field imparted by the electron-donating methyl groups at the 5-position on the imidazole moieties and undergoes a partial spin transition with an estimated T1/2 = 390 K. In contrast, 1b is stabilized in the high-spin state because of the strong steric hindrance when the three methyl “legs” are changed from the 5-position to the 4-position on the imidazole moieties. In addition, a new complex, 2, without methyl groups attached to the imidazole rings is introduced and characterized to further corroborate the steric influence on the spin state. Complex 2 exhibits a gradual spin-crossover behaviour with T1/2 = 258 K. Moreover, the diverse spin states of these complexes are computationally studied using the DFT method. The results of the calculations are consistent with the experiments, which prove that the competition of the electronic effect and steric crowding influence the spin states.

The first SCO@SCO core–shell nanomaterials have been synthesized by the step-by-step microemulsion method. The observed gyroscopic core–shell nanocomposites exhibit three-step spin crossover behaviour with thermal hysteresis at around room temperature. This offers an efficient and novel strategy for the development of multistable SCO materials.

A new class of chiral tetrahedral iron(II) cages were prepared from subcomponent self-assembly with high diastereoselectivity. The cages can be interconverted through imine exchange. The chiral cages displayed a spin transition close to room temperature, and the transition temperatures were affected by the substituent and uncoordinated solvents.

Four pairs of enantiomers of water-stable tetrahedral metal–organic cages [Ni4L6]8+ were facilely synthesized. They efficiently stabilized antiparallel G-quadruplex DNA with moderate enantioselectivity, and displayed promising cytotoxicity against the human cancer cell lines HCT116, HepG2 and MCF-7. These results provide a new insight into the rational design of chiral G-quadruplex-based anticancer agents.

An effective single crystal to single crystal transformation from a tetrahedral Ni cage to an FeNi cage was demonstrated. The iron(II) centers of the FeNi cage can be induced to display spin crossover behaviors with an increasing amount of Fe(II) ions. The SCSC metal-center exchange provides a powerful approach to modify solid magnetic properties.

A fascinating polythreaded coordination network formed by 1D crankshaft shaped chains threading into a 2D undulated sheet in a one-over/one-under interweaving fashion was reported, in which the 2D layer exhibits an unusual polyknotted entanglement containing triple-stranded molecular braids.

Through multi-component self-assembly of chiral phenylethylamine, 1-alkyl-2-imidazolecarboxaldehyde and iron(II) ions, two couples of enantiomeric iron(II) complexes 4R, 4S, 5R and 5S with the formula of fac-Λ or Δ-[Fe(L)3]2+(L = R or S-1-phenyl-N-(1-alkyl-1H-imidazol-2-ylmethylene)ethanamine) have been designed and synthesized as building blocks. Further binary cocrystallization of the prefabricated enantiomers enabled us to construct spin crossover co-enantiomers 4R5R and 4S5S, racemates 4RS and 5RS, and co-racemate 4RS5RS. Compared with 4R in a high spin state and 5R with spin crossover at 291 K, the co-enantiomers 4R5R exhibited gradual spin crossover at a higher temperature of 301 K, and the racemic alloys showed hysteresis loops induced by desolvation above room temperature. It was demonstrated that molecular chirality could be used effectively for stereochemical engineering of spin crossover materials. In addition, crystal packing, intramolecular π–π stacking, intermolecular C–H⋯π interactions and solvent effects were elucidated to be responsible for the distinct spin crossover properties. This collective structural and magnetic study not only enriched the spin crossover library, but also provided a full comparison of optically pure, homochiral, and racemic materials with similar molecular structures.