N,N-Diarylthiazol-5-amines: Structure-Specific Mechanofluorochromism and White Light Emission in the Solid State

A range of N,N-diarylthiazol-5-amines having a 4-pyridyl group on a thiazole ring were developed, and their photophysical properties were elucidated. Their synthesis was achieved by applying our methods to the combination of N-arylmethyl secondary thioamides and N,N-diarylthioformamides. This enabled us to obtain amines with different types of aromatic groups on the nitrogen atom. Their absorption and emission spectra in solution were examined. The 4-pyridyl group gives higher polarity to the amines. The solid-state emissions of the amines were also evaluated. Several amines showed mechanofluorochromism (MFC). A 4-pyridyl group on a thiazole ring was a requisite for the expression of MFC properties. Although N-(5-thiazolyl) N,N-di(2-naphthyl)amines did not exhibit MFC by grinding of the pristine powder, white-light emission was observed when the ground powder was fumed with acetone vapor.