The impact of π-π stacking interactions on photo-physical properties of hydroxyanthraquinones

The impact of p-p stacking interactions on photo-physical properties of hydroxyanthraquinone (HA) has been investigated using the density functional (DFT) and time-dependent density functional theory (TD-DFT) calculations in the gas phase and solution media. The vertical transition is characterized with strong HOMO-LUMO transition in the complexes. The intramolecular hydrogen bond (IHB) made in the HA and p-p complexes is strengthened after S-0 ? S-1 excitation, such that the proton transfers is facilitated in the first excited state. The complexes exhibit an exothermic excited state intramolecular proton transfer (ESIPT) in the solution media, which is a barrierless process for some complexes. The p-p stacking interaction affects the absorption and emission bands of HA, and provides a large Stokes shift. This indicates the desirable fluorescence properties of p-p complexes, which are cross-validated by geometries, potential energy curve scannings, electronic and vibrational spectra, and frontier molecular orbital analyses.

Automated summary

The impact of p-p stacking interactions on the photo-physical properties of hydroxyanthraquinone (HA) was studied using DFT and TD-DFT calculations in the gas phase and solution media. The complexes exhibited strong HOMO-LUMO transitions and strengthened intramolecular hydrogen bonds after excitation. In solution media, the complexes showed an exothermic and barrierless excited state intramolecular proton transfer (ESIPT). The p-p stacking interaction affected the absorption and emission bands of HA, providing a large Stokes shift, indicating desirable fluorescence properties.