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.