STRUCTURE AND PROPERTIES OF COPPER-(II) AND COPPER-(I) COMPLEXES WITH 2,6-BIS[2-(THIOPHENE-2-YLMETHYLIMINO)ETHY] PYRIDINE

Positive-ion FAB mass spectroscopy. elemental analysis. EPR spectroscopy and X-ray diffraction analysis have revealed the structure oi the copper(ll) complex of 1:2 (Cu:L) stoichiometry obtained by mixing in methanol 1 equivalent of Cu(ClO4)(2) . 6H(2)O and 1 equivalent of 2,6-bis[2-(thiophen-2-ylmethylimino)ethyl]pyridine ylmethylimino)ethyl]pyridine (L). The copper(II) ion is co-ordinated to six nitrogen atoms in an octahedral arrangement not involving the thiophene S atoms. The planes of the two trans pyridine subunits are perpendicular (94 degrees); the Cu-N bond distances are 1.924 and 1.983 Angstrom for the pyridine. 2.098. 2.118 and 2.284, 2.330 Angstrom for the imine indicating slight distortion in the structure. Cyclic voltammetry;in acetonitrile showed reversible behaviour for the [Cu(II)L(2)](2+)-[Cu(I)L(2)]+ couple, and the redox potential E was -0.61 V vs. 10 mmol dm(-3) Ag-Ag+ in MeCN. Spectroscopic investigation of acetonitrile solutions having a 1:1 Cu:L molar ratio indicated the formation of species with 1:1 overall stoichiometry. The electrochemical measurements revealed that these complexes decompose during the electron transfer leading to the [Cu(II)L(2)](2+)-[Cu(I)L(2)](+) redox process.