Mechanochromic luminescence of 4-[bis(4-methylphenyl)amino]benzaldehyde

The title compound was found to exhibit mechanochromic luminescence; the fluorescent color of the crystalline powder was changed from light blue to greenish yellow by grinding and then returned to the original by keeping at room temperature. The phenomenon was suggested to be due to formation of the supercooled liquid state of the material by grinding and following recrystallization.