Synthesis, structure, spectroscopic and redox properties of copper(II)-N-3,5-Bu2tphenylsalicylaldinine complexes: Crystal and molecular structure of bis(N-3,5-Bu2t-phenylsalicylaldininato)copper(II)

New bulky bis(N-3,5-Bu2tphenyl-R-salicyaldiminato)copper(II) complexes X were synthesized and characterized by analytical, spectroscopic (IR, UV/Vis, EPR), electrochemical methods, and their chemical redox reactivity were studied. X-ray structural analysis of 1 revealed that the CuN2O2 coordination core forms a distorted square-planar geometry with a cis-N2O2 donor set which is not expected for analogous complexes. The UV/Vis and EPR results indicate that X complexes have a tetrahedrally distorted square-planar structure in the solid state and in solution. In the chemical oxidation of X by (NH4)2Ce(NO3)6 along with disappearance of their EPR spectra, the appearance of new Cu(II) patterns at g = 2.169–2.189 for all X and radical signals in the cases of 5 and 6 were detected. The chemical reduction of some X complexes was accompanied by the disappearance of their EPR signals. The separation in peak potentials (ΔEp) for complexes X are in order 4 < 3 < 2 < 1 < 6. The electrochemical results suggested that the complex 4 has the highest electrochemical rate assuming both the Cu(II) and Cu(I) forms appear in a similar geometrical configuration, so the electron transfer does not require larger reorganization of the complex in complex 4.

The synthesis, spectroscopic (NMR, IR, UV/Vis, ESR) and electrochemical properties and redox behaviors of new bis(N-3,5-Bu2t-R-salicylaldiminato)copper(II) complexes are described. Oxidation of some complexes with (NH4)2Ce(NO3)6 results in the generation of Cu(II)-phenoxyl radicals. As confirmed by X-ray crystallography complex 1 (R = H) has a slightly distorted cis-CuN2O2 coordination polyhedron.Figure optionsDownload as PowerPoint slide