Département de chimie moléculaire

To complete the elucidation of the electrochem. properties of MnII-bis(terpyridine) complexes in MeCN and evaluate the influence of the bulkiness of the terpy substituents, the oxidn. processes of [MnII(L)2]2+ (L = terpy for 2,2':6',2''-terpyridine, pTol-terpy for 4'-(4-methylphenyl)-2,2':6',2''-terpyridine and tBu3-terpy for 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine) were studied in aq. (1 M) MeCN soln. In this medium, exhaustive oxidns. at 1.10-1.20 V vs. Ag/Ag+ release two electrons per mol. of initial complex and lead to clean dimerization processes with the quant. formation of the oxo-bridged binuclear [Mn2 IVO2(L)2(H2O)2]4+ complex for L = tBu3-terpy and of the tetranuclear [Mn4 IVO5(L)4(H2O)2]6+ complexes for L = terpy and pTol-terpy. The formation of the tetranuclear complex with the tBu3-terpy deriv. is prevented by the steric hindrance induced by the bulkiness of the tert-Bu groups, as confirmed by mol. mechanics calcns., as well as by their strong electron-donating properties. All these electrogenerated multinuclear complexes were fully characterized in soln. by UV-visible and EPR spectroscopy. A markedly improved chem. synthesis of [Mn4 IVO5(terpy)4(H2O)2]6+ is also reported. [on SciFinder(R)]