Quantum chemical and solvatochromism study of NSAIDs in neat and binary solvent systems

The solvatochromism, solvation, and excited-state dipole moment of the nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen (IBP) and ketoprofen (KEP) have been investigated using UV–Visible absorption and fluorescence spectroscopic techniques. A bathochromic shift is observed in the emission wavelength of IBP and hypsochromic shift in KEP. The solvatochromic behavior of both molecules has been analyzed in detail by correlating their spectral properties with the Lippert–Mataga function and solvent polarity parameters ([Formula: see text]), Kamlet–Taft and Catalan multiple linear regression methods. Preferential solvation (PS) studies of both molecules were carried out in a tetrahydrofuran (THF)–water (H2O) solvent mixture. The results, based on the PS method, are discussed in terms of the variation of transition energy ([Formula: see text]) with the mole fraction of water, the solvation index ([Formula: see text]), and the proportionality coefficient ratio ([Formula: see text]). The excited-state dipole moments of the molecules were estimated using both DFT and experimental methods. The influence of solute polarizability on the estimated excited-state dipole moment and the change in dipole moment was analyzed using the Bilot–Kawski approach. This study reveals the distinctive photophysical properties of these molecules, underscoring their relevance beyond biomedical and pharmaceutical applications.