Abstract
Constructing multi-dimensional hydrogen bond (H-bond) regulated single-molecule systems with multi-emission remains a challenge. Herein, we report an excited-excited intramolecular transfer (ESIPT) featured chromophore (HBT-DPI ) that shows flexible emission tunability via the multi-dimensional regulation of intra- and intermolecular H-bonds. The feature of switchable intramolecular H-bonds is induced via incorporating two hydrogen bond acceptors into a single-molecule system, HBT-DPI,allowing the “turn on/off” of ESIPT process by forming isomers with distinct intramolecular H-bonds. In response to different solvent environments, the obtained four types of crystal/cocrystals vary in the contents of isomers and the molecular packing modes, which are mainly guided by the intermolecular H-bonds, exhibiting non-emissive features or emissions ranging from green to orange. Moreover, we demonstrate the practical utility of this fluorescent material for visualizing hydrophobic/hydrophilic areas on large-scale heterogeneous surfaces of modified PVDF membranes and quantitatively estimate the surface hydrophobicity, providing a new approach for hydrophobicity/hydrophilicity monitoring and measurement.
Introduction
Hydrogen bonding, as one of the most ubiquitous molecular interactions, plays important roles in modulating the properties and functions of advanced materials for numerous applications. 1-8Especially, in the field of luminescent materials, the modulation of hydrogen bonds (H-bond) is linked with performances in the aspects of photoswitching,9,10 emission wavelength,11,12 luminescence lifetime,13,14 and quantum yield.15,16 Since the energy of ordinary H-bonds is normally less than 15 kcal/mol,17 environmental stimuli such as the temperature,18humidity,19 vapor,20,21force,22,23 and solvents24,25 can interfere with the established H-bonds of the chromophores, making their emissions environment-sensitive.