Facial and meridional geometrical isomers of tris(2-methylimidazol-4-yl-methylideneaminobenzyl)iron(II) with Δ- and Λ-con figurations and their enantio-discriminative assembly via imidazole ... chloride hydrogen bonding and spin cross-over properties (Reprinted from Polyhedron, vol 44, pg 194, 2012)

A bidentate 2-methylimidazol-4-yl-methylideneaminobenzyl ligand (HLMe-Renz) reacts with (FeCl2)-Cl-II center dot 4H(2)O 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 [Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot solvent. Meridional and facial geometrical isomers, i.e., mer-[Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot 1.5H(2)O (1 center dot PF6.1.5H(2)O) and fac[Fell( [Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot EtOH.H2O (2-PF6 center dot EtOH center dot H2O), were selectively crystallized from methanol and ethanol solutions, respectively. fac-[Fe-II (HLMe-Benz)(3)]C1 center dot PF6 center dot H2O (2.SbF6 center dot 1.H2O) and fac-[Fe-II (HLMe-Benz)(3)]C1 center dot EtOH center dot H2O(2.ClO4 center dot EtOH2O) are synthesized in ethanol, using the corresponding anions. Each Fell ion has an octahedral coordination geometry with N6 donor atoms from three bidentate ligands. All three imidazole groups in both thefac- and mer-[Fe-II (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.PF6.1.5H(2)O forms a heterochiral two-dimensional (2D) network structure comprised of cyclic [Fe-II (HLMe-Benz)(3)](2+) ... Cl-}(4) units with an Delta Delta Delta or Lambda Lambda Delta configuration; the PF6- ions occupy the spaces between the 2D layers. All the fac-complexes have isomorphous cubane-like tetrameric structures, i.e.,.Cl},. C114. The tetranuclear structure comprises four homo-chiral {fac-[Fe-II (HLMe-Benz)(3)](2+) ... Cl-3(-)} 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 Mossbauer 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. (C) 2013 Published by Elsevier Ltd.