Use of acid-base and redox chemistry to synthesize cobalt(III) and iron(III) complexes of a partially deprotonated triprotic imidazole-containing Schiff base ligand: Hydrogen bound 1D linear homochiral and zig-zag heterochiral supramolecular complexes

Aerial reaction of cobalt(II) perchlorate with H₃(1) [H₃(1) is the tripodal ligand derived from the condensation of tris(2-aminoethyl)amine with three equivalents of imidazole-2-carboxaldehyde] in methanol and [FeH₃(1)(ClO₄)₂] with Fe(1) in acetonitrile results in the formation of [CoH₂L](ClO₄)₂·H₂O and [FeHL]ClO₄·CH₃CN, respectively. Mössbauer spectroscopy and variable temperature magnetic susceptibility indicate that [FeHL]ClO₄·CH₃CN is a low spin iron(III) species. Both complexes were characterized by EA, IR, and single crystal structure determinations. Both complexes crystallize in the centrosymmetric monoclinic space group, P2₁/c, so both enantiomers of the chiral complex are present. The supramolecular features of these complexes, caused by the partial deprotonation of the ligand and the resultant formation of imidazole-H···imidazolate hydrogen bonds, are different. [FeHL]⁺ forms hydrogen bonds with molecules from adjacent cells of like chirality. This results in a linear homochiral array of iron complexes. In contrast, [CoH₂L]²⁺ forms hydrogen bonds with a molecule from the same cell and one from another cell resulting in an 1D alternating heterochiral zig-zag chain.