Mechanofluorochromism of 4-[bis(9,9-dimethylfluoren-2-yl)amino]benzaldehyde

The titled compound exhibited mechanofluorochromism, the fluorescent color of the crystalline sample altering from light blue to greenish yellow by mechanical stress such as grinding. The state obtained by grinding the crystalline powder was more stable than that for the parent compound, 4-[bis(4-methylphenyl)amino]benzaldehyde, which we have previously reported. It was suggested that the change in emission color observed in the present study was due to morphological change from crystalline state to amorphous state by grinding and the state obtained by grinding was stabilized by increasing the glass-transition temperature of the material.

► 4-[Bis(9,9-dimethylfluoren-2-yl)amino]benzaldehyde exhibited mechanofluorochromism.
► New series of mechanofluorochromic materials.
►  The mechanofluorochromism observed here was due to morphological change.
► State obtained by grinding was stabilized by increase in the Tg of the material.
► Ease of conformational change in the condensed state is an important factor.