Photocatalytic oxidation of various organic substrates using multinuclear Ru(II)-polypyridyl complexes

Over the past few years, an extensive usage of transition metal complexes as photoactive SET (single electron transfer) agents in the synthetic organic chemistry has opened new doors to reinvent the already known organic transformations as well as to create different paths for previously unattainable reaction products. Especially, Ru(II)-polypyridyl complexes have acted as a pillar owing to an inherent advantage of their triplet excited-state involved in various photoactivities. Though the photophysics of Ru(II) complexes has been well documented within inorganic community, they are less exploited for the problems of interest to the synthetic organic chemists. Recent development in this field suggests that a connection between organic synthesis and photoactive metal complexes might lead to successful outcomes in both the research areas. Notably, in contrast to the rigorous employment of mononuclear Ru(II)-polypyridyl complexes, the multinuclear species have been less well-studied and their fundamental optoelectronic properties and applications are relatively under explored. However, the multinuclear Ru(II) species offer more promising photophysical features compared to the mononuclear analogues via fine-tuning of the bridging ligands and/or the individual metal centres. Recently, such species have enabled essential breakthroughs in the research fields of photocatalysis, light-emitting devices (LEDs), photodynamic therapy (PDT), smart materials, optical sensors and so on. In this study, we offer an overview of the photophysics of multinuclear Ru(II)-polypyridyl complexes with an aim to explain their ground- and excited-state features, along with related light-driven electron/energy transfer processes for potential catalytic oxidation of various organic substrates such as alcohols, sulfides, alkenes, etc.