Influence of Solvent Environment on the Photophysical Properties of Maleamic Acid and Maleimide Derivatives

Abstract

Absorption and fluorescence spectra of novel maleamic acid (E)-4-oxo-4-(4-((2-oxooxazolidin-4-yl)methyl)phenylamino)but-2-enoic acid (OMPBA) and its maleimide derivative 1-(4-((2-oxooxazolidin-4-yl)methyl)phenyl)-1H-pyrrole-2,5-dione (OMPPD) were recorded in a series of eighteen solvents of increasing polarity at room temperature (25 °C). A large Stokes shift indicates a bathochromic fluorescence band shift for both molecules. The photoluminescence properties and intramolecular charge transfer (ICT) behavior of OMPBA and OMPPD were analyzed. In the case of OMPPD, ICT contributes to a larger extent towards positive solvatochromism compared to OMPBA. Ground-state and singlet excited-state dipole moments of OMPBA and OMPPD were calculated using solvatochromic methods proposed by Bilot and Kawski, Lippert and Mataga, Bakhshiev, Kawskii and Chamma and Viallet, and also Reichardt. The ground state dipole moment was found to be larger than for the singlet excited state for both molecules. Optimized geometry and HOMO–LUMO energies of OMPBA and OMPPD have been determined by DFT and TDDFT/B3LYP/6-311G (d, p). The HOMO–LUMO energy gap was calculated from cyclic voltammetry and compared with theoretical values with good agreement. GCRD parameters such as ionization potential (IP), electron affinity (EA), electronegativity χ, chemical potential (μ), chemical hardness (η), chemical softness (s) and electrophilicity (ω) were calculated for OMPBA and OMPPD.