Donor-acceptor type π-conjugated diphenylsulfone derivatives showing diverse fluorescence response to mechanical force

Abstract Two donor-acceptor type π-conjugated fluorophores DPS-OCZ and DPS-OPTZ consisting of diphenylsulfone unit as the electron-accepting and carbazole or phenothiazine moiety as the electron-donating were synthesized and characterized. They showed evident ICT characters endowed both fluorophores with a prominent solvatochromic effect, with emitting color tuning by changing the solvent polarity. Spectral studies and theoretical calculations proved the presence of D-A type conjugated structures of DPS-OCZ and DPS-OPTZ. Interestingly, both fluorophores showed diverse fluorescence response to mechanical force (bathochromic shift for DPS-OPTZ or hypsochromic shift for DPS-OCZ). Based on the results of XRD patterns and X-ray single crystals analyses, the reason is as follows: the planarization of the molecular conformation and the resulting planar ICT upon grinding were responsible for the bathochromic shift in the PL spectra of DPS-OPTZ. In contrast, the highly ordered structure was destroyed, partly changed the packing mode, resulting in the hypsochromic shift in PL spectra of DPS-OCZ. The current work presented a strategy of imposing molecular feature screening for realizing diverse fluorescence response to mechanical force.