We focus on the study of ultrafast excited state intramolecular proton transfer (ESIPT) in variuos flavones and chromones derivatives like 3-Hydroxyflavone (3-HF), 5-Hydroxyflavone (5-HF) and 3-Hydroxychromone (3-HC) and 5-Hydroxychrone (5-HC). Analysis of spectral features associated with ESIPT enol-keto tautomerization is the first step in our study. As the proton transfer (or tautomerization) occurs on the vibrational motion timescales, potential energy surfaces along each of the O-H vibrational modes are explored using computational techniques. Subsequently, quantum molecular simulations on computed potentials provide us the mechanistic pathways and timescales of proton transfer.
2) Ultrafast Intersystem Crossing in Organic Molecules
Our interests are to identify the pathways involved in an indirect intersystem crossing in molecular systems. Naphthalene, perylenediimide and pyrene derivatives are the model systems currently under investigation to explore the role of near-degenerate higher singlet-triplet excited states.
Evaluation of structural distortions and associated reorganization energies of photoexcited para-linked phenylenes (linear and cyclic) is carried out by DFT and TDDFT methods. Active vibrational modes responsible for excited-state intramolecular vibrational relaxation are to be identified in these molecular systems to provide an accurate description of energy/electron transfer process.