Sedigheh Hashemnia

A new Co (II) complex of 6,13-disubstituted 1,4,8,11-tetraaza[14]annulene derivative has been syn-thesized by template condensation reaction of 2-(1-quinolinium-1-yl) trimethinium salt (B) with1,2-diaminopyridine in the presence of Co (II) acetate in DMF. The electrochemical behavior of the metalcomplex showed a CoII/CoIredox couple at about ?0.99 V vs. Ag/Ag in DMF solvent. Axial ligation of N-donor ligands such as pyridine and imidazole was found to shift the reduction potential of CoII/CoIto morenegative potential. The binding of N-donor axial ligands to the metal complex was monitored by measur-ing changes at about 458 nm (maximun absorption of the metal complex) and shifts in the CoII/CoIredoxcouple potential upon addition of various concentrations of the N-donor axial ligand. Results showedthat the number of axial ligand molecules bound to the metal complex is ?1 and the oxidized state ofcobalt (CoII) is more stabilized than the reduced state (CoI) in the presence of the axial ligand. The metalcomplex also showed catalytic activity toward hydrogen peroxide decomposition in the presence of theN-donor axial ligand.