Synthesis, electrochemical and photophysical properties of heterodinuclear Ru-Mn and Ru-Zn complexes bearing ambident Schiff base ligand

While ruthenium tris(diimine) complexes have been extensively studied, this is not the case with ruthenium bis(diimine)X(2) complexes where X represents a pyridinyl-based ligand. The synthesis of a new complex ([2][PF6](2)) bearing two ambident Schiff base ligands (HL) constituted by the assembly of phenol and pyridinyl moieties is reported. Thanks to the heteroditopic property of HL, compound [2](2+) was used as an original metalloligand for the coordination of a redox-active (Mn(III)) and redox-inactive (Zn(II)) second metal cation affording three heterodinuclear complexes, namely, [(bpy)(2)RuL(2)Mn(acac)][PF(6)](2) ([3][PF(6)](2); acac = acetylacetonate), [(bpy)(2)RuL(2)Mn(OAc)][PF(6)](2) ([4][PF(6)](2), OAc = acetate), and [(bpy)(2)RuL(2)Zn][PF(6)](2) ([5][PF(6)](2)). The influence of the second metal with regard to the photophysical and electrochemical properties of the ruthenium bis(diimine) X(2) subunit was then investigated. In the case of Ru(II)-Mn(III) heterodinuclear complexes, a partial quenching of the luminescence was observed as a consequence of an efficient electron transfer process from the ruthenium to the manganese. EPR and spectrophotometric analyses of the oxidized species resulting from the one-electron oxidation of compounds [3](2+) and [4](2+) showed the formation of a Mn(IV) species for [3](2+) and an organic free radical for [4](2+).