In this study, we report a deep red emissive organic crystal that displays high contrast fluorescence switching under mechanical- and thermal stimulation. Upon mechanical grinding, the pristine red emissive crystals of 1R (λem = 667 nm) transformed to green emissive crystalline powder (λem = 550 nm) with remarkable hypsochromic shift of wavelength, Dλ = 117 nm. Melting of 1R leads to green emissive amorphous solid (λem = 555 nm) with wavelength shift of Dλ = 112 nm. Upon fuming with different solvents, the amorphous melt solid transform to different polymorphs having distinct emission characters. The structural relationship between different emissive states is investigated with the aid of X-ray diffraction and other spectroscopic studies, which clearly demonstrate the role of ordered molecular packing and intermolecular interaction in determining their diverse optical response.
Manas K. Panda, Nayana Ravi, P. Asha, A. P. Prakasham
CrystEngComm, 2018, DOI: 10.1039/C8CE00696B.