Bi- and tetranuclear ligational deeds of a polyaza macrocycle having four diazine (N2) bridging components headed for CoII, NiII, CuII and ZnII ions: An emphasis on electrochemistry of non-innocent ligand system

Novel bi- and tetranuclear Co^II, Ni^II, Cu^II and Zn^II complexes having diazine bridging units have been prepared and characterised on the basis of analytical and spectroscopic techniques. With the help of electronic spectra and magnetic moment measurements, it is predicted that the Co^II and Ni^II complexes have octahedral geometry while Cu^II and Zn^II complexes found to be square pyramidal. Present Zn^II and Cu^II complexes are binuclear in nature, where as Co^II and Ni^II complexes are tetranuclear with feeble antiferromagnetic exchange interactions. UV–visible spectral studies, in the range 275–425 nm, evidence the significant blue shift in π → π* transition which provide the ease of stabilization of bonding molecular orbitals in the complexes. All complexes are monomeric in nature. Ligand and all complexes were found to be electrochemically active compounds. One electron transfer process is observed in ligand similarly, there is no significant change in the cyclic voltammograms of Co^II and Zn^II complexes, while Cu^II and Ni^II complexes show one and two electron transfer redox behaviours, respectively in the present macrocyclic ligand field.