Luminescent solvent-free liquids based on Schiff-base boron difluoride complexes with polyethylene glycol chains

A series of Schiff-base boron difluoride complexes with polyethylene glycol chains were synthesized and their photophysical properties were examined. These complexes maintained the solvent-free liquid state even at room temperature and their glass transition temperatures ( T g ) were determined to be around −40 °C. The complexes showed blue to yellow luminescence under UV irradiation in the solvent-free liquid state with good emission quantum yields ( Φ ) of up to 0.26. The luminescence colour could also be tuned by dissolving organic dyes in the blue luminescent liquid sample. Density functional theory (DFT) and time-dependent (TD) DFT calculations were performed to further understand the photophysical properties. Multi-colour luminescent solvent-free liquids were developed based on boron difluoride complexes with N -PEGylated Schiff-base ligands.