Synthesis and characterization of ruthenium and rhenium dyes with phosphonate anchoring groups

Re(L1)–Re(L3), a series of rhenium(I) tricarbonyl chloride complexes with bpy-R2 derivatives L1–L3 (bpy =2,2’-bipyridine, R represents the substitution at the 4- and 4’-positions), and their corresponding trishomolepticRu(L1)3–Ru(L3)3 as well as heteroleptic ruthenium(II) complexes Ru(tbbpy)2(L1) andRu(tbbpy)2(L2) have been synthesized and characterized. Their applicability as immobilizable metal–organic chromophores in solar and photosynthesis cells is enabled by R, since it includes phosphonicester groups as precursors for potent phosphonate anchoring groups. Conjugated linkers (phenylene andtriazole moieties) serve as distance control between bpy and the anchor. Photophysical and electrochemicalstudies reveal pronounced effects of the aryl substitution. These effects were further investigatedusing resonance Raman experiments and supported by theoretical calculations. After hydrolysis thetriazole containing Re(L2) was successfully immobilized on NiO, suggesting that its application in photovoltaiccells is feasible. The solid state structures of Re(L0), Re(L0hydrolyzed), Re(L1) and Re(L2) are reportedin this paper, enabling the determination of the distances and intermolecular interactions.