A folded mechanochromic organic fluorophore based on thianthrene-fused coumarin.

The powder samples of a novel thianthrene-fused coumarin dye (6,7-BDTC) demonstrated pronounced mechanochromic luminescence, shifting from light-blue to green emission upon mechanical stimulation. X-ray crystallography of polymorphs with different emission colors revealed that this responsiveness originates from variations in the packing mode induced by the D-A type folded structure. These results demonstrate that introducing a folded π-conjugated framework into the coumarin core enables control over the packing mode and emission properties in the solid state.