The excited state behaviors of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde system in aprotic solvents

Highlights: • Hydrogen bond OH···N should be enhanced for BTHMB in aprotic solvents in S₁. • Photo-induced charge redistribution promotes ESIPT tendency for BTHMN system. • Gap between HOMO and LUMO reveal difficulty level of ESIPT reaction in solvents. • Ultrafast ESIPT process of BTHMB can be regulated by aprotic solvent polarity. In this work, we adopt theoretical calculation manner to explore excited state dynamical behaviors of intramolecular hydrogen bond and proton transfer (ESIPT) process for a novel organic 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) system. Insights into changes of chemical geometries and infrared (IR) vibrational behaviors, we judge excited state hydrogen bonding strengthening for BTHMB. Our estimated hydrogen bonding energies further check the intramolecular hydrogen bond of BTHMB should be strengthened much stronger in polar solvent. Photo-induced charge reorganization and negative charges concentrated on N moiety facilitate ESIPT reaction for BTHMB. Probing into frontier molecular gap, we infer in polar solvent, intramolecular hydrogen bonding activities and molecular reactional kinetic initiatives become more obvious. By means of restricted optimization, we further construct potential energy curves (PECs) along with ESIPT direction. In addition, via searching reactional transition state (TS) and IRC simulations, we present the ultrafast ESIPT reaction of BTHMB could be regulated via solvent polarity.