Executive Summary : | Pincer-complexes are essential tools for organic synthesis due to their long-term stability and easy functionalization. The current paradigm for metal-pincer catalysts focuses on a single active metal site with ligands that impart steric and electronic tunability for substrate binding and activation. However, less attention has been given to the molecular level understanding of secondary sphere activation of small molecules. Secondary interactions are ubiquitous in biological systems and are largely present in metalloenzymes. This secondary coordination sphere incorporation allows for stabilizing the small-molecule substrate and reactive intermediate via non-covalent interaction, altering redox properties, and promoting functional activity in the system. This work aims to develop new triazine-based H-bond donors containing a metal-pincer system for substrate binding and activation of small molecules. The study aims to stabilize the unusual square planar geometry of low oxidation metal ions and investigate their reactivity in catalysis. The work also assays visible-light-driven photoisomerization of azobenzene and captures the distorted cis-isomer in the coordination pocket. Another target is to synthesize highly electron-deficient triazine containing metal-pincer complexes by incorporating/substituting the electron-withdrawing -CF3 group into the ligand backbone. This enhances Lewis acidity, stability, reactivity at the metal site, lipophilicty, and hydrogen bonding ability in the catalysis. The proposed electron-poor metal pincer catalysts provide access to selective hydrogenation of polyarenols, biomass-conversion catalysis, electrophilic CH borylation of heteroarene, CO2 activation, and utilization by a N/B Lewis pair. |