Mononuclear, Tetra-, Penta-3d Molecular Clusters Based on the Variability of SS-1,2-Bis(1H-benzimidazole-2-yl)-1,2-ethanediol Ligand Arising from Hydroponic and Hydrothermal Conditions: Structure, Crystal Growth, and Magnetic Properties

Four compounds Co(SS-H(2)bzirmd-H)(2)center dot CH3OH center dot 2H(2)O (1), Zn-4(SS-H(2)bzimed-H)(4)(NO3)(4)center dot 5H(2)O (2), Co-5(Hbzimed-H)(6)Cl-4 center dot 2.5H(2)O (3), Ni-5(Hbzimed-H)(6)Cl-4 center dot 4H(2)O (4) (SS-H(2)bzimed = SS-1,2-bis(1H-benzimidazole-2-yl)-1,2-ethanediol; Hbzimed = 1,2-bis(1H-benzimidazol-2-yl)-1,2-ethenol) have been synthesized by methods of alternative hydroponic and hydrothermal reactions, and their crystal structures were determined. Room temperature reaction of SS-H2bzimed with Co(NO3)(2)center dot 6H(2)O yielded compound 1 which crystallizes in the chiral orthorhombic space group C222(1), where SS-H2bzimed ligands act as facially tridentate ligands through both bis-benzimidazole nitrogen atoms and one deprotonated hydroxyl group. By using Zn(NO3)(2)center dot 6H(2)O instead of Co(NO3)(2) center dot 6H(2)O, under refluxed stirring at 80 degrees C, compound 2 was obtained similarly to 1 which crystallizes in the chiral monoclinic space group C2, showing a Zn-4(mu(3)-O](4) cubic core constructed by four monodeprotonated, mu(3)-kappa N,O:kappa O,O':kappa N',O'-SS-H(2)bzimed ligands. Under 140 degrees C at hydrothermal. conditions, the SS-H2bzimed ligand unexpectedly changes to Hbzimed by an in situ intramolecular dehydration coupling reaction, and the neonatal ligands bridge metal systems into two kinds of rare single crystal microtubes constructed by a trigonal bipyramid M-5[mu-O](6) (M = COII : 3, Ni-II : 4) core where each apical Oh metal atom is linked to equatorial T-d metal atoms through Six mu(2)-kappa N,O:kappa N',O-Hbzimed-H ligands. Magnetic studies show that 3 exhibits spin-canting behavior below 10 K, whereas 4 shows only simple antiferromagnetic coupling. Such magnetic behavior of 3 mainly arises from O-h-T-d mixed geometries of pentameric Co(II) ions, which can result in relatively noncompensated moments, according to different efficient spins of Co(II) at very low temperature and the Dzyaloshinski-Moriya interaction. A discussion of the coordination properties of H(2)bzimed ligands upon different geometries of the central ions, and a probable mechanism for in situ reaction of ligand and the formation of single crystal microtubes is provided.