Computational Investigation on ESIPT-driven Luminescence of Imidazo[1,2-a]pyridine Derivatives Regulated by Inter/Intramolecular Hydrogen bonding

Abstract

Abstract The three newly synthesized imidazopyridine derivatives bearing inter/intramolecular hydrogen bond were computationally investigated. The quasi stable seven-membered ring systems of the compounds assisted by the intramolecular hydrogen bond exhibited distinct luminescence depending on the surrounding media; in solution, in frozen solution and in solid state. The interesting luminescent properties were studied by means of a series of quantum chemical calculations; i.e., DFT, TDDFT, CASSCF/CASPT2, ADC(2), CC2 and CCSD(T). The stability of the quasi π-conjugated rings was found to be regulated by the delicate balance between intramolecular steric hindrance and intra/intermolecular hydrogen bond strength. The excited state dynamics was explored by the surface hopping trajectory calculations which reproduced the ESIPT process in the first excited singlet state.