Enhanced aggregation induced emission by H-bond between the barbiturate molecules containing hydroxyl group

Abstract

Barbiturates had been widely studied as a molecule with aggregation induced emission (AIE) phenomenon, but barbiturates as a group with multiple hydrogen bond donor and acceptor sites, the relationship between intermolecular hydrogen bond and AIE phenomenon has not been mainly studied. In this paper, a new barbiturate fluorescence molecule BNOH with hydroxyl group was designed and synthesized in order to analyze the relationship between hydrogen bond and molecular AIE phenomenon by increasing the functional group (–OH) that was easy to form hydrogen bond. By spectroscopic analysis, BNOH had structural torsion in aqueous mixed solution, which led to fluorescence decrease, while in aprotic mixed solvent, there was strong AIE phenomenon. DFT and TD-DFT calculations at the B3LYP/6-31G (d) were performed for a deeper understanding of optical transitions. In addition, in order to investigate the difference of its fluorescence phenomenon, two other barbiturate derivatives were synthesized and their spectra were compared with BNOH. The relationship between hydrogen bond and AIE phenomenon of barbiturates was proved, and the fluorescence mechanism of BNOH in organic solvent was proposed and determined. We believe that this study will not only increase the understanding of barbiturate AIE compounds, but also contribute to the study of the important role of hydrogen bonds in the fluorescence phenomenon of barbiturate AIE compounds.