Cobalt and nickel complexes of a hypodentate ligand, 2-[3-(pyridylamino)phenylazo]pyridine: Synthesis, structure and properties

Abstract

Reactions of the salts MCl₂∙nH₂O (M = Co, Ni), with the extended azoaromatic ligand, 2-[3-(pyridylamino)- phenylazo]pyridine (HL¹) afford the mononuclear complexes, [M(L¹)₂]m⁺ ( M=Co, m=1 and M=Ni, m=0) in high yields. X-ray structure of the nickel complex is reported. The structural analysis has revealed that two monoanionic ligands [L¹]⁻ bind the metal centre in a N₆-fashion using pairs of pyridyl-N, azo-N and deprotonated arylamido-N atoms. The two N(py) atoms (of the 3-amino pyridyl function) remain as pendents and unused. Positive ion ESI mass spectra of the complexes provide evidence for the integrity of the complexes in solution. Their UV-visible spectra consist of intense transitions in the low energy area of the visible region. Cyclic voltammetry of these complexes displays multiple reversible waves. The Co(III)/Co(II) reduction and Ni(II)/Ni(III) oxidation in their respective complexes appear at - 0.24 and 0.57V, respectively.