Synthesis, Electrochemical Properties and Spectroscopic Studies of Mono and Dinuclear Zn(II) Polypyridyl Complexes with Phenylcyanamide Ligands

Several novel mononuclear Zn(II) complexes, [Zn(bpy)L2], where bpy=2,2’-bipyridine and L=monoanions of phenylcyanamide (pcyd), 4-methylphenylcyanamide (4-Mepcyd), 3,5-dimethylphenylcyanamide(3,5-Me2pcyd),4-methoxyphenylcyanamide(4-MeOpcyd), 3,5-dimeth-oxyphenylcyanamide (3,5-MeO2pcyd), 3-chlorophenylcyanamide (3-Clpcyd), 2,3-dichlorophenyl-cyanamide (2,3-Cl2pcyd), 4-bromophenylcyanamide (4-Brpcyd), 1-naphthylcyanamide (1-ncyd), azophenylcyanamide (apcyd) and a dinuclear Zn(II) complex, [{Zn(terpy)}2(μ-adicyd)](PF6)2, where terpy = 2,2´:6´,2´´-terpyridine and adicyd = azodi (phenylcyanamide) dianion have been synthesized and characterized by elemental analysis, UV-vis, IR, 1H-NMR spectroscopic techniques and cyclicvoltammetry.The presence of only one sharp and intense absorption band for υ(N=C=N) around 2100-2180 cm-1 for all the monomer complexes provide evidence that both cyanamide legend are equivalent in the solid state and coordinated end-on by nitride nitrogen to Zn(II). This is also indicated by 1H-NMR spectra of the complexes. UV-vis spectra show one MLCT band that are associated with Zn(II)-pyridyl chromophores(t2g6 →π*). Blue shift of this band with increasing the polarity of solvent from CH3OH to DMSO is the reason for this assignment. The Zn(II) ion is redox innocent therefore, two irreversible oxidation peaks at positive potential and one reduction couple at the negative potential are assigned to sequential oxidation of two phenylcyanamide ligands and reduction of bipyridine, respectively.