Highlighting the role of the medium in DFT analysis of the photophysical properties of ruthenium(II) polypyridine-type complexes

In order to test the pertinence of the density functional theory to interpret the photophysical properties of ruthenium(II) polypyridine-type complexes, DFT and TDDFT calculations are performed both on the isolated molecule and in solution media described by the dielectric-like polarized continuum model (PCM). This study is focused on three isoelectronic complexes: Ru(bpy)(2)(PhenImHPh)](2+) (II), where PhenImHPh represents the 2-(3,5-ditertbutylphenyl)imidazo4,5-f]1,10]phenanthroline ligand, as well as Ru(bpy)2(PhenImPh)]+ (I), and Ru(bpy)(2)(PhenImH2Ph)](3+) (III), obtained by changing the protonic state of the imidazole ring. The structural and electronic properties of the ground and lowest triplet states are fully characterized in vacuo and in water solution, and the absorption spectra in the visible region are also investigated by TDDFT. The theoretical data are compared to the electrochemistry, UV-visible, and photophysical experiments to assess the validity and limits of each type of calculation. The choice of the functional is also discussed.