Three Bis-BODIPY Analogous Diruthenium Redox Series: Characterization and Electronic Structure Analysis.

The dianion derived from (2Z,6Z)-3,7-diphenyl-N2,N6-di(pyridin-2-yl)pyrrolo[2,3-f]indole-2,6(1H,5H)-diimine (H2BL), a modified BODIPY ligand precursor, is shown to be capable of bridging two metal complex fragments RuL2, L=2,4-pentanedionato (acac(-)), 2,2'-bipyridine (bpy) or 2-phenylazopyridine (pap) in [Ru(acac)(2)Ru(mu-BL)Ru(acac)(2)] (1/2), [Ru(bpy)(2)Ru(mu-BL)Ru(bpy)(2)](ClO4)(2)([3](ClO4)(2)) and [Ru(pap)(2)Ru(mu-BL)Ru(pap)(2)](ClO4)(2)([4](ClO4)(2)). The compounds, including a diastereoisomeric pair1(meso) and2(rac) were spectroscopically and structurally characterized. Reversible electron transfers as revealed by cyclic and differential pulse voltammetry allowed for an EPR and UV-vis-NIR spectroelectrochemical investigation of several neighboring charge states. Together with susceptibility measurements and TD-DFT calculations the assignment of oxidation states reveals that1,2are diruthenium(III) species which can be oxidized or reduced by one electron whereas3(2+)and4(2+)contain ruthenium(II) and get reduced or oxidized mainly at the dianionic bridge (3(2+)) or are reduced at the ancillary ligands pap (4(2+)).