Theoretical insights into photo-induced behaviors associated solvent polarity effects for HDMTP fluorophore: A TDDFT study

In this work, the influence of solvent polarities on the excited-state intramolecular proton transfer (ESIPT) process of 2,2′-((1E,1′ E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(4-(1,2,2-triphenylvinyl)phenol) (HDMTP) is systematically investigated in three solvents of distinct polarities (hexane, tetrahydrofuran, and acetonitrile) through DFT and TDDFT methodologies. We mainly elucidate the excited-state double proton transfer (ESDPT) mechanism in the HDMTP fluorophore. We analyze the geometric configuration, infrared (IR) vibrational spectra, and core-valence bifurcation (CVB) indexes to verify the enhancement of hydrogen bonds in the excited state. Meanwhile, we detect the HOMO and LUMO orbitals to investigate the influence of charge redistribution on the proton transfer process. The PESs are scanned to testify a stepwise ESDPT mechanism for HDMTP systems. We also propose that the decrease of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the HDMTP system based on the calculated potential energy barriers for HDMTP in hexane, tetrahydrofuran, and acetonitrile solvents.