Conclusion
In summary, we proposed to extend the diversity in constructing single-molecule ESIPT systems by the multi-dimensional regulation of intra- and intermolecular H-bonds. The model molecule, HBT-DPI , reported in this work contains two functional groups, diphenylimidazole (DPI ) and benzothiazole (BT ), which render the feature of switchable intramolecular H-bonds. Two isomers, OH-DPI andOH-BS , were obtained respectively in solvents with or without H-bond acceptors, possessing distinct intramolecular H-bonds that influence the ESIPT process to the emissive properties of the two isomers. In response to different solvent environments, four types ofHBT-DPI crystal/cocrystals (HBT-DPI-N ,HBT-DPI-Y , HBT-DPI-G , and HBT-DPI-O ) were further obtained via crystal growth as a result of the regulation of both intra- and intermolecular H-bonds. The multi-dimensional H-bonds regulation largely influenced the molecular packing of HBT-DPImolecules, resulting in multimode crystal structures that are non-emissive or emit variable fluorescence ranging from green to orange. This work provides new insights into the H-bonds regulation induced structure-packing-performance relationship, which offers a molecular-level design strategy to construct single molecule light-emitting materials with multi-emissions. Furthermore,HBT-DPI was shown to map the hydrophobic/hydrophilic areas on large-scale heterogeneous surfaces and quantitatively estimate the surficial hydrophobicity/hydrophilicity, offering a new approach advantageous over the conventional contact angle measurement.