Efficient energy transfer and metal coupling in cyanide-bridged heterodinuclear complexes based on (bipyridine)(terpyridine)ruthenium(II) and (phenylpyridine)iridium(III) complexes

We report a series of cyanide-bridged, heterodinucleariridium(III)−ruthenium(II) complexes with the generalized formula [Ir((R2)2-ppy)2(CN)(μ-CN)Ru(bpy)-(tpy-R1)]PF6 (ppy = 2-phenylpyridine, bpy = 2,2′-bipyridine,and tpy = 2,2′:6′,2″-terpyridine). The structural, spectroscopic,and electrochemical properties were analyzed in the context of variation of the electron-withdrawing (e.g., −F, −Br, −CHO)and -donating (e.g., −Me) and extended π-conjugated groups at several positions. In total, ten dinuclear complexes and the appropriate model complexes have been prepared. Theiridium(III)-based emission is almost fully quenched in thesecomplexes, and only the ruthenium(II)-based emission isobserved, which indicates an efficient energy transfer towardthe Ru center. Upon oxidation of the Ru center, the fluorinated complexes 2 exhibit a broad intervalence charge-transfertransition in the near-infrared region. The complexes are assigned to a weakly coupled class II system according to the Robin−Day classification. The electronic structure was evaluated by density functional theory (DFT) and time-dependent DFTcalculations to corroborate the experimental data.