TDDFT investigation of solvent polarity related excited state intramolecular proton transfer in 2-(4′-hydroxyphenyl)-3-hydroxybenzo[g]quinolone

Abstract

In view of potential applications of fluorescent probe for the novel 2-(4′-hydroxyphenyl)-3-hydroxybenzo[g]quinolone (2HP3HBQ) chemosensor, herein, we mainly focus on exploring effect of solvent polarity on ESIPT behavior for 2HP3HBQ. Firstly, we compare infrared (IR) vibrational behaviors and geometric parameters, we check intramolecular hydrogen bond O1-H2⋯O3 could be strengthened in S1 state. Combining bond critical point (BCP) with empirical formula for predicting bond energy, we present nonpolar solvents are more conducive to strengthening hydrogen bonds. Studying frontier molecular orbitals (MOs), we clarify intramolecular charge transfer (ICT) in excited molecule, and charge redistribution facilitates ESIPT. In particular, nonpolar solvent is more propitious to ESIPT. Via keeping two coordinates, we construct potential energy surfaces (PESs) by restrictive optimization. Separating potential energy curves (PECs) along with O1-H2⋯O3, we clarify solvent-polarity-regulated ESIPT mechanism for 2HP3HBQ system. We sincerely wish our work paves the way for designing highly efficient fluorescent probes for 3HBQ derivatives.