Correlation of Electrode Behaviour and Spectral Properties of Some Mixed-Ligand Complexes of Copper(ll)

Department of Chemistry, University of Allahabad, Allahabad-211 002

Analyses of the electrode behaviour with regard to half-wave potential 'E_{\(\frac{1}{2}\)}', formalrate constant 'K_\(f\) ', activation energy of rearrangement \(Q\) _\(e\) and activation energy of diffusion, \(Q\)_\(D\) \(vis\)-\(a\)-\(vis\) spectral behaviour of mixed-ligand complexes of Cu(Il) with 2,2'-bipyridyl and 1,10-phenanthroline as primary ligands and some aliphatic, aromatic, amino acids and phenols as secondary ligands have been made. In aqueous potassium nitrate solution, the complexes containing bipyridyl as primary ligand give two-electron, single-step reduction wave while the complexes containing phenanthroline as primary ligand give two step electro-reduction wave at dme. All the systems are observed to be diffusion controlled and irreversible. A correlation of electrode behaviour with the spectral parameters has been attempted. It has been observed that the half-wave potential shifts towards more negative side as the ligand field shifts towards higher energy side. The rate constant shows a decreasing trend in conformity with this. A possible mecha­nism of electron transfer has been suggested on the basis of orientation of orbitals towards the electrode. The activation energy of diffusion shows a direct relationship with the energy difference between binary and ternary complexes in a particular series.