Bridge-Dependent Donor-Metal-Acceptor-Metal-Donor (D-M-A-M-D) Systems: From Charge Transfer to Electron Transfer in Dioxolene-Ge-Diimine Complexes.

Synthesis and structural characterization of a family of germanium-dioxolene complexes with ditopic N-donor ligands (L-L) (L=1,2-bis(pyridin-2-ylmethylene)hydrazine L=1,6-bis-(pyridin-2-yl)-2,5-diaza-1,5-hexadiene, L=N,N-bis(pyridin-2-ylmethylene)-1,4-benzenediamine, L=N,N-bis(pyridin-2-ylmethylene)-(biphenyl)-4,4-diamine, L=2,2'-azopyridine) is reported. The reaction of germanium bis-catecholate with bridging ligands L - L, differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36CatGe)L (36Cat=dianion of 3,6-di-tert-butylcatechol) 1-4 of DMAMD type (donor-metal-acceptor-metal-donor) with a charge transfer in the UV-Vis region. In opposite, the interaction of the 36CatGe with 2,2'-azopyridine (L) results in the two-electron transfer from the donor 36Cat ligands to the azopyridine bridge forming stable open-shell complex 5 [(36SQ)(36CatGe)](L) (36SQ=radical-anionic semiquinonate ligand).