Role of Spacers in Molecularly Linked RuRh Dyads: A Comparative Synthetic and Ultrafast Spectroscopic Investigation.

Supramolecular photocatalysts consisting of photosensitizer (PS), bridging ligand (BL), and catalytic center (CAT) have garnered significant attention in solar fuel applications. In this study, the photophysics and photocatalytic properties of two Ru(II)-based dinuclear complexes, specifically [(tbbpy)(2)Ru(p(Ph)(n)p)Rh(Cp*)Cl](3+) (n = 0, 1; Ru(pp)Rh for n = 0 or Ru(p(Ph)p)Rh for n = 1; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, Cp* = pentamethylcyclopentadienyl, Ph = phenyl, p = 1,10-phenanthroline), are investigated. These complexes are studied as model complexes only differing by the distance between PS and CAT and thus allows a selective investigation of the influence of spacers in light-driven catalysis. A joint synthetic, spectroscopic, and theoretical approach, incorporating time-resolved absorption and emission spectroscopy, resonance Raman (rR) spectroscopy, density functional theory (DFT), and time-dependent (TD)DFT calculations, allows for comprehensive structural, electrochemical, photophysical, and photochemical characterization. Our findings suggest that minor structural variations in the intramolecular photocatalytic system significantly impact photocatalytic activity and system stability.