Effect of Different Substituted Groups on Excited-State Intramolecular Proton Transfer of 1-(Acylamino)-anthraquinons

This study uses density functional and time dependent density functional theory to investigate excited-state intramolecular proton transfer (ESIPT) reactions of 1-(acylamino)-anthraquinons (AYAAQs). We report that hydrogen-bond intensity in excited states is affected by the different AYAAQs substituted groups in ethanol for the first time. Absorption and emission spectra were also calculated and show that the changed AYAAQs spectra can be explained perfectly by combining the AYAAQs potential energy curves. The theoretical spectral values show good agreement with experimental results. The theoretical calculations indicate that proton transfer reactions can be implemented in the first excited (S-1) state. The hydrogen-bond strengthening mechanism was confirmed, where hydrogen-bond interaction acts as the driving force for the ESIPT reactions. Therefore, ESIPT reactions are more likely to occur from AAAQ -> CAAQ -> DCAQ -> TFAQ molecules, which are different substituted derivatives.