Research Projects

1. Motivation for the Proposal: Catalysis remains foundational in producing everyday chemicals, yet conventional thermal methods often demand harsh conditions and have high carbon footprints. Photocatalysis has emerged as an eco-friendly alternative, enabling thermodynamically challenging conversions under milder conditions and with lower environmental impact. Among these, metallaphotoredox catalysts the Ir(III)/ Ni(II) photocatalytic couple -mediated cross-coupling has ushered in a new era for synthesizing C–C, C–N, and C–X bonds (X = halogen, oxygen). However, mechanistic understanding remains fragmented. Concurrently, host–guest photocatalysis using coordination cages or covalent organic frameworks (COFs) allows activation of even weakly polarized C(sp³)–H bonds under visible light, yet its underlying mechanisms remain largely unexplored 2. State of the Art Review: A. Ir(III)/Ni(II) Photocatalysis – International Scenario: Leading research groups (Molander, Doyle, MacMillan, Hadt, Shaik, Chen) have proposed conflicting mechanistic models involving homolytic Ni–X bond cleavage via triplet–triplet energy transfer, oxidative or reductive single-electron transfer (SET), and Ni(III) intermediates fragmenting to X· radicals. Yet the exact initiation route (homolysis vs. SET; excited-state lifetimes; role of intersystem crossing) remains unclear. Knowledge gaps: Key unknowns include excited-state dynamics, ISC/IC processes, solvent and spin-orbit coupling effects, and substrate dependence. B. Host–Guest Photocatalysis of C–H Bonds – Global & Indian Scenario: Fujita’s Pd₆L₄ coordination cages catalyze photo-oxidation of alkanes under mild conditions. Mechanistic suggestions include ultrafast host-to-guest charge transfer initiating oxidation, but deeper understanding is lacking. Dasgupta’s team extended this to arenes using Pd₆L₄ and metal-free cages, implicating light-triggered proton-coupled electron transfer (PCET). Yet the precise sequence: charge separation, radical intermediate formation, oxygen involvement remains unresolved. No computational studies yet describe excited-state dynamics or charge-transfer mechanisms driving oxidation. 3. Project Objectives and Innovation: A. Ir(III)/Ni(II) Mechanistic Elucidation: (I) Simulate excited-state dynamics to distinguish between homolytic and heterolytic pathways. (II) Compute ISC/IC rates; identify singlet–triplet crossing points. (III) Use QM/MM and quantum chemical tools to study bond cleavage, radical coupling, solvent interactions, and Ir(III)* / Ni(II) activation. Innovation: Apply non-adiabatic dynamics simulations and develop machine-learned potentials (MLPs) tailored to excited-state transition-metal chemistry. Insights will guide photocatalyst design for pharma and synthetic chemists. B. Computational Study of Host–Guest Photocatalysis: (I) Map charge-transfer excited states, PCET pathways, and radical intermediates in nanocages and COFs using static and dynamic quantum chemical methods. (II) Explore O₂’s role post-light-induced charge separation, including radical oxygen species. Innovation: Establish a framework linking photoinduced charge dynamics, substrate oxidation, and host effects. Supports design of metal-free photooxidative systems in porous molecular architectures. 5. Summary: By integrating quantum dynamics, machine-learned potentials, and QM/MM modelling, this project pioneers theoretical studies of two emerging photocatalytic frontiers—transition-metal photoredox and host–guest supramolecular systems. The outcomes will demystify elusive mechanisms and offer new paths for extending synthetic scope.