Unexpected room-temperature phosphorescence from a non-aromatic, low molecular weight, pure organic molecule through the intermolecular hydrogen bond

Abstract

Efficient pure organic room temperature phosphorescence (RTP) materials have drawn considerable attention. So far, most pure organic RTP molecules are aromatic compounds, and nonconjugated molecules are really scarce. The only few reported non-aromatic organic phosphorescence materials are polymers without confirmed subtle structures, and there are no reports concerning non-aromatic organic small molecules with persistent RTP. Here, we report an example of a pure non-aromatic organic small molecule, cyanoacetic acid, that shows unexpected persistent RTP behavior with RTP lifetime as long as 862 ms. According to the CAA crystal and theoretical calculations, the presence of strong intermolecular hydrogen bonds is the key factor for its persistent RTP effect. This discovery demonstrates a clear relationship between the molecular structure, packing mode and RTP effect in the non-aromatic system, which will largely extend the current pure organic RTP systems to deeply investigate the origin of light emission.