SYNTHESES, CHARACTERIZATION AND OXYGENATI ON PROPERTIES OF 4 BENZIMIDAZOLYL-CONTAINING DICOPPER(I) COMPLEXES

This paper reports the syntheses of four benzimidazolyl-containing lig ands: ortho-bis [N, N'-bis(2'-benzimidazolyl-methyl) amino]-trans-cycl ohexane (OCTB) and its three alkyl-substituted derivatives. Dicopper(I ) complexes 1 similar to 4 were respectively prepared through the reac tions of the ligands with [Cu(CH3CN)(4)]ClO4. Elemental analyses, IR s pectra and H-1 NMR show that the compositions of the ligands and the c omplexes are the same as desired. UV-vis spectra indicate that complex es 1 similar to 4 can combine with dioxygen. The colorless solutions o f the complexes in DMF show an uptake of oxygen and give green solutio ns with a wide absorption peak about at 700 nm. Addition of ascorbic a cid (AA) results in decolorization of the solutions and the cycle can be repeated three or four times. Equilibrium constants, Delta H degree s and Delta S degrees of oxygenation reactions of the complexes in DMF are obtained by manometric oxygen-uptake measurements. We consider th at the steric hindrance on N atom of benzimidazole is unfavourable to oxygenation. The electron-donating substituents on N atom would increa se the electron density of coordination atom and further the central i on Cu(I) and make the oxygenation more easier. The oxygenation rates i n different solvents are in the order of DMF > DMSO > Py.