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 (L1‐L5) (L1 = 1,2‐bis(pyridin‐2‐ylmethylene)hydrazine L2 = 1,6‐bis‐(pyridin‐2‐yl)‐2,5‐diaza‐1,5‐heхаdiene, L3 = N,N‐bis(pyridin‐2‐ylmethylene)‐1,4‐benzenediamine, L4 = N,N‐bis(pyridin‐2‐ylmethylene)‐(biphenyl)‐4,4‐diamine, L5 = 2,2’‐azopyridine) is reported. The reaction of germanium bis‐catecholate with bridging ligands L1 – L4, differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36Cat2Ge)2L1‐4 (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 36Cat2Ge with 2,2’‐azopyridine (L5) results in the two‐electron transfer from the donor 36Cat2‐ ligands to the azopyridine bridge forming stable open‐shell complex 5 [(36SQ)(36CatGe)]2(L5)2‐ (36SQ = radical‐anionic semiquinonate ligand). Molecular structures of compounds 3 and 5 were determined by single crystal X‐ray diffraction analysis. Electronic structures of complexes 1‐5 were studied by means of DFT calculations.