Synthesis, solvatochromism and dipole moment in the ground and excited states of substitute phenol derivative fluorescent Schiff base compounds

Abstract

Three new fluorescent o-hydroxyaryl Schiff base derivatives are synthesized and their structures are characterized by NMR and FTIR spectroscopies. In this study, the solvent effect on the absorption and fluorescence spectral properties, Catalán and Taft-Kamlet solvatochromism models, and electric dipole moments in the ground and excited states, are investigated for synthesized compounds. Specific and non-specific solute–solvent interactions are investigated using Catalán and Taft-Kamlet solvatochromism models in various solvents with different polarities. Taft-Kamlet and Catalán solvatochromism models derived for absorption spectra indicate that solvent dipolarity/polarizability (?*) and solvent polarity (SP) are dominant in controlling absorption spectral shifts. As a result of solute–solvent interactions, absorption spectra exhibit positive solvatochromism, while fluorescence spectra show negative solvatochromism with the increase of solvent polarity. The ground state dipole moment is determined using the Bilot–Kawski method, and the excited state dipole moment is calculated using the Bilot–Kawski, Lippert–Mataga, Bakhshiev, modified Bilot-Kawski and Reichardt correlation methods. The dipole moments estimated in both ground and excited states confirm that Schiff base compounds are more polar in the excited state. The frontier molecular orbitals (HOMO and LUMO), molecular electrostatic potential (MEP), density of states (DOS) and solvent accessibility surfaces (SAS) of these compounds have been calculated using the DFT/B3LYP/6-311++G(d,p) level of theory. © 2021 Elsevier B.V.