Département de chimie moléculaire

We report on a new heterobimetallic manganese-ruthenium complex, in which a MnII bis(terpyridine) center is covalently linked to two RuII tris(bipyridine) units. By electro- or photoinduced oxidn. of this Mn center, high-valent multinuclear oxo-bridged manganese species can be generated. These were unambiguously identified by electrochem. and UV/Vis and ESR (EPR) spectroscopy. In a CH3CN soln. of water (1 M), the dinuclear core, [(H2O)(terpy)MnIII($μ$-O)2MnIV(terpy)(H2O)]3+ (terpy = 2,2':6',2''-terpyridine) is first obtained by dimerization, and can be further oxidized to give rise to the tetranuclear core, [(H2O)(terpy)MnIV($μ$-O)2MnIV(terpy)($μ$-O)(terpy)MnIV($μ$-O)2MnIV(terpy)(H2O)]6+. These cores are connected to two and four [Ru(bpy)3]2+ units, resp. The second dimerization process is prevented when coordinating CF3CO2- anions are present in soln., as oxidn. of the initially generated species, [(CF3CO2)(terpy)MnIII($μ$-O)2MnIV(terpy)(CF3CO2)]+, produces the stable dinuclear [(CF3CO2)(terpy)MnIV($μ$-O)2MnIV(terpy)(CF3CO2)]2+. All these species are generated in high yields either by exhaustive electrolysis or continuous visible-light irradn. A diazonium salt is required as the irreversible electron acceptor for photochem. expts. Mol. mechanics calcns. confirm that the formation of the higher nuclearity complex with a tetranuclear Mn central core linked to four Ru unit is feasible. The Ru-Ru distances are long enough to preclude possible steric hindrance of the Ru units. [on SciFinder(R)]