Fluorescent Non-conventional D-π-A Organogel for Aniline Sensing.

A non-conventional organogelator with rigid chemical structure was designed based on 2,6-distyryl-4H-pyran skeleton in this work. Aided by balanced intermolecular π-π interactions, the gelator was capable of gelate pure chloroform and mixed solutions containing chloroform. Interestingly, introducing long hexyl chains in the gelator's structure makes it lose the gelation ability, indicating that alkyl chain is not always favorable auxiliary group for gelation. The gel network was selectively responsive to aniline, which was manifested by aniline-triggered gel collapse. Notably, the gel exhibited remarkable fluorescence blue-shift upon exposure to aniline, rather than quenching, exhibiting ratiometric fluorescence response. The selective response to aniline was due to that aniline could break the original intermolecular π-π interactions in the gel state, providing a unique example of ratiometric gel sensor for aniline.