Molecular design and synthesis.
To enable the multi-dimensional regulation of H-bonds, DPI was attached to a central HBT core to obtain the model ESIPT chromophore HBT-DPI . Although both DPI and BTcontain unsaturated N atoms, endowing them with excellent H-bond accepting capability, whereas the presence of sulfur atom in BTweakens its hydrogen accepting ability.49,50 Moreover, the DPI group contains an extra H-bond donor (N-H) that can form either an intramolecular H-bond with the oxygen of the phenol core or an intermolecular H-bond with other molecules, which could extend the possible molecular packing behaviors in the solid state. By such a molecular design, the manipulation of multi-dimensional H-bonds (intra- and intermolecular) would render the environment sensitive material with a variety of photophysical properties. The ESIPT chromophoreHBT-DPI was synthesized by three-step reactions according to Supplementary Scheme S1 and characterized using 1H NMR, 13C NMR and high-resolution mass spectrometry (Figures S20-22).