Executive Summary : | This project will involve developing a novel approach in gold catalysis via the design and construction of a new class of bimetallic catalysts - gold-ruthenium/iridium bimetallic dyads. These photosensitizer-catalyst assemblies will feature gold-based core as the catalytic site which will conjugately bridged with Ru and Ir photosensitizers. This dyad construction is aimed at activating the gold center through vectorial charge transfer mediated gold photosensitization. However, despite the underlying potential, to the best of my knowledge, there exists no report wherein an intramolecular gold photosensitization has been utilized to facilitate the arduous Au(I)/Au(III) catalytic cycle to realize organic transformations. First, I will synthesize Ir and Ru photocatalysts with a vacant pendant binding site for the chelation of gold. But the mainstay to find the perfect conjugated linker to bridge Au and Ir/Ru centers is to provide a photostable binding site for gold, prevent back electron transfer and act as energy/electron storage. Hence, rational screening with computational studies of bridging ligands will help to find perfect a phosphine ligand, NHC ligand, and N as well as N^N type ligands which could construct Au(I)-Ru(II)/Ir(III) bimetallic dyads. Initially, the synthesis of the four dyads is proposed which can further be modulated as per their photophysical and electrochemical requirement. Furthermore, the photophysical and electrochemical properties of these novel heterobimetallic gold assemblies will be studied in detail. These studies will help to demonstrate the effect of different bridging ligands on the oxidation and reduction potential of gold thereby allowing the modulation of photophysical and electrochemical properties of gold dyads through the modification of bridging ligands. Heteronuclear bimetallic Au(I) dyads and Au(III) will have distinct but unique properties, and will be utilized in cross-coupling reactions, 1,2-functionalization reactions, and substrate sensitization. To conclude, using the paradigm of vectorial charge transfer between photosensitizer and gold centers, conjugately bridged gold-photosensitizer(Ir/Ru) bimetallic dyad assemblies will surpass the energy barriers to attain gold photosensitization which will pave the way for novel energy-efficient pathways in organic synthesis. |