Time‐dependent density functional theory study on the absorption spectrum of Coumarin 102 and its hydrogen‐bonded complexes

Abstract

The effect of both solvent polarity and hydrogen bonding (HB) on the electronic transition energy of Coumarin 102 (C102) has been examined using the time-dependent density functional theory (TDDFT). Solvent effect on both geometry and electronic transition energy is evaluated using the polarizable continuum model (PCM). A linear relation of the absorption maximum of C102 with the solvent polarity function Δf is found using the TDDFT-PCM method for all solvents except dimethyl sulfoxide. The solvent polarity and the type B HB between the carbonyl oxygen and solvent hydrogen atom make the absorption wavelength redshift, whereas the type A HB between the amino nitrogen atom and solvent hydrogen atom has an opposite effect on the absorption wavelength. The calculated absorption wavelengths of C102 with two type B HB between the carbonyl oxygen and solvent hydrogen atom are in excellent agreement with experimental measurements. The solvatochromism of C102 is analyzed in terms of the Kamlet-Taft equation and the parameters s and a are discussed.