Transition metal complexes of 2,6-bis(imidazol-2-yl)pyridine and its aliphatic derivative

Abstract

Cationic complexes [Mn(ipi)2]Cl2·CH3OH·H2O (1), [Co(ipi)2]Cl2 (2) and [Ni(ipi)2]Cl2 (3) and neutral complex [Co(C18ipi–H)2]0 (4) were synthesized based on tridentate ligand 2,6-bis(imidazol-2-yl)pyridine (ipi) and its deprotonated derivative 2-(1H-imidazol-2-yl)-6-(1-n-octadecyl-1H-imidazol-2-yl)pyridine (C18ipi), respectively. The complexes were characterized by elemental and thermogravimetric analysis, FT-IR and electronic spectroscopy. The molar conductivity of the dilute methanol solutions (C=10−2–10–4M) of cationic complexes was investigated under normal conditions. The X-ray crystallographic studies of the complexes 1–3 show a similarly distorted octahedral geometry around the 3d-metal ions. Interestingly, compound 3 can be obtained in monoclinic (3m) and orthorhombic (3o) crystal modifications. The structures of ionic complexes show complicated networks of hydrogen bonds between the cationic [M(ipi)2]2+ cores and Cl− anions, as well as solvent molecules in the case of MnII. While the CoII-ion in 2 is in high spin state, in the complex 4 it is in the low spin state, as envisaged by the magnetic and spectroscopic studies.