Facial and meridional geometrical isomers of tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) with ¦¤- and ¦«-configurations and their enantio-discriminative assembly via imidazole?chloride hydrogen bonding and spin cross-over properties
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- 作者：Daisuke Furushou ; Tomotaka Hashibe ; Takeshi Fujinami ; Koshiro Nishi ; Hiroaki Hagiwara ; Naohide Matsumoto ; Yukinari Sunatsuki ; Masaaki Kojima ; Seiichiro Iijima
- 关键词：Iron(II) complex ; Bidentate ligand ; Geometrical isomer ; Optical isomer ; Hydrogen bond ; Spin crossover
- 刊名：Polyhedron
- 出版年：2012
- 出版时间：31 August, 2012
- 年：2012
- 卷：44
- 期：1
- 页码：194-203
- 全文大小：1072 K
文摘
A bidentate 2-methylimidazol-4-yl-methylideneaminobenzyl ligand (HLMe-Benz) reacts with FeIICl2¡¤4H2O and NaPF6 at a 3:1:1 molar ratio to yield a tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) chloride hexafluorophosphate solvate with the formula of [FeII(HLMe-Benz)3]Cl¡¤PF6¡¤solvent. Meridional and facial geometrical isomers, i.e., mer-[FeII (HLMe-Benz)3]Cl¡¤PF6¡¤1.5H2O (1¡¤PF6¡¤1.5H2O) and fac-[FeII(HLMe-Benz)3]Cl¡¤PF6¡¤EtOH¡¤H2O (2¡¤PF6¡¤EtOH¡¤H2O), were selectively crystallized from methanol and ethanol solutions, respectively. fac-[FeII(HLMe-Benz)3]Cl¡¤SbF6¡¤H2O (2¡¤SbF6¡¤H2O) and fac-[FeII(HLMe-Benz)3]Cl¡¤ClO4¡¤EtOH¡¤H2O (2¡¤ClO4¡¤EtOH¡¤H2O) are synthesized in ethanol, using the corresponding anions. Each FeII ion has an octahedral coordination geometry with N6 donor atoms from three bidentate ligands. All three imidazole groups in both the fac- and mer-[FeII(HLMe-Benz)3]2+ cations are hydrogen-bonded to neighboring three Cl? ions, and each Cl? ion is hydrogen-bonded to three imidazole groups of three neighboring complex cations; this results in the formation of hydrogen-bonded assembly structures. mer-Complex 1¡¤PF6¡¤1.5H2O forms a heterochiral two-dimensional (2D) network structure comprised of cyclic {mer-[FeII(HLMe-Benz)3]2+?Cl?}3 units with an ¦¤¦¤¦« or ¦«¦«¦¤ configuration; the PF6? ions occupy the spaces between the 2D layers. All the fac-complexes have isomorphous cubane-like tetrameric structures, i.e., {fac-[FeII(HLMe-Benz)3]2+?Cl?}4. The tetranuclear structure comprises four homo-chiral fac-¦¤- or fac-¦«-[FeII(HLMe-Benz)3]2+ cations and four Cl? ions interconnected by twelve imidazole-chloride hydrogen bonds to form a chiral cubane supramolecule that encapsulates one counter anion. In the crystal lattice, the cubane-like tetramers with opposite chiralities are alternately arrayed. The temperature dependence of the magnetic susceptibilities and M?ssbauer spectra reveal that the fac-complexes show incomplete spin crossover behavior, while the mer-complex shows a gradual spin crossover between high-spin (HS, S = 2) and low-spin (LS, S = 0) states.