Synergetic effect of atomic electronegativity, substitution position and solvent polarity on the ESIPT process of 1-(trifluoroacetylamino)anthraquinone derivatives: a DFT study

Abstract

This study systematically investigates the synergetic effect of atomic electronegativity, substitution position and solvent polarity on the regulation of the excited-state intramolecular proton transfer (ESIPT) mechanism in 1-(trifluoroacetylamino)anthraquinone (TFAQ) derivatives. Through analyses of geometric parameters, infrared (IR) vibrational spectra, reduced density gradient (RDG) plots, and topological characteristics, we confirmed that the intramolecular hydrogen bonds (IHBs) are enhanced from the ground state (S₀) to the first singlet excited state (S₁) in cyclohexane (CYH), dimethyl sulfoxide (DMSO) and water (H₂O). More specifically, the IHBs in the S₁ state weaken with increasing electronegativity. IHBs are strengthened with increasing solvent polarity from CYH to DMSO. The meta- and para-substituted derivatives display a stronger IHB enhancement effect in DMSO and H₂O than the ortho-substituted derivatives. Fluorescence spectral analyses revealed that TFAQ, TFAQ-N, m-TFAQ-N, and p-TFAQ-N display dual fluorescence emission in DMSO and H₂O. Finally, the scanned potential energy curves (PECs) indicate that the enhanced electronegativity of substituent atoms imposes certain restrictions on ESIPT, making meta- and para-substituted derivatives conducive to ESIPT. We anticipate this study will provide valuable insights for the design and development of novel TFAQ-based white-light organic light-emitting diodes (WOLEDs).