Photophysical study of some 3-benzoylmethyleneindol-2-ones and estimation of ground and excited states dipole moments from solvatochromic methods using solvent polarity parameters

Abstract

► Photophysical studies of 3-benzoylmethyleneindol-2-ones in a series of different solvents. ► Ground and excited states dipole moments. ► Analysis of the ground and excited state processes. ► Study of pH effect on 3-benzoylmethyleneindol-2-ones. 3-Benzoylmethyleneindol-2-ones, isatin based chalcones containing donor and acceptor moieties that exhibit excited-state intramolecular charge transfer, have been studied in different solvents by absorption and emission spectroscopy. The excited state behavior of these compounds is strongly dependent on the nature of substituents and the environment. These compounds show multiple emissions arising from a locally excited state and the two states due to intramolecular processes viz. intramolecular charge transfer (ICT) and excited state intramolecular proton transfer (ESIPT). Excited-state dipole moments have been calculated using Stoke-shifts of LE and ICT states using solvatochromic methods. The higher values of dipole moments obtained lead to support the formation of ICT state as one of the prominent species in the excited states of all 3-benzoylmethyleneindol-2-ones. The correlation of the solvatochromic Stokes-shifts with the microscopic solvent polarity parameter ( E T N ) was found to be superior to that obtained using bulk solvent polarity functions. The absorption and florescence spectral characteristics have been also investigated as a function of acidity and basicity (Ho/pH) in aqueous phase.