ELECTROCHEMICAL REDUCTION OF BIS(BETA-DIKETONES) - 1,10-DI(ALPHA-CYCLOHEXANONE)DECANE-1,10-DIONE AND 3,14-DIACETYLHEXADECANE-2,15-DIONE - CHARACTERIZATION AND ELECTRON-PARAMAGNETIC-RESONANCE PROPERTIES OF THEIR ELECTROGENERATED MONONUCLEAR COPPER(II) COMPLEXES

The preparation and characterization of the bis(beta-diketone) 1,10-di (alpha-cyclohexanone)decane-1,10-dione (H2L1 = 1) and 3,14-diacetylhex adecane-2,15-dione (H2L 2= 2) ligands, are reported. A direct electroc hemical generation of Cu(ll)L complexes is achieved. The electrochemic al reductions of 1 and 2 have been investigated in tetra-hydrofuran at a dropping mercury electrode. Voltammetric, coulometric and UV-visibl e results indicate that their two-electron reduced form ultimately gen erates the corresponding anions (L1)2- and (L2)2-. The reaction of (L1 )2- and (L2)2 -with Cu(ll) trifluoromethanesulfonate gives the corresp onding 1 : 1 complexes (Cu(ll)L1 = 1') and (Cu(ll)L2 = 2'). In frozen- chloroform solutions, the latter complexes show well resolved electron paramagnetic resonance (EPR) spectra. The observed hyperfine splittin gs due to the nuclear spin I = 3/2 of the copper ion allow the determi nation of the following magnetic parameters: g(parallel-to) = 2.304, g (perpendicular-to) = 2.062, a(parallel-to) = 142 x 10(-4) cm-1, a(perp endicular-to) = 25.2 x 10(-4) cm-1 for 1', and g(parallel-to) = 2.277. g(perpendicular-to) = 2.048, a(parallel-to) = 160 x 10(-4) cm-1, a(pe rpendicular-to) = 22.4 x 10(-4) cm-1 for 2'. The UV-VIS absorption spe ctra and the results obtained from the experimental and simulated EPR spectra indicate that the complex 1' has a square-planar geometry wher eas 2' is a square-planar distorted complex.