Design, synthesis, crystal structures, and photophysical properties of tetraphenylethene-based quinoline derivatives

The incorporation of aggregation-induced emission (AIE) luminogens provides a molecule with enhanced fluorescent emission in the solid state. A representative AIEgen compound is tetraphenylethene (TPE). A series of new conjugates of quinolone derivatives with TPE units (1a - 1f) was synthesized and characterized. The influence on the photophysics of 1a - 1e with a variety of functional groups was investigated systematically by spectroscopic methods and simulated by density-functional theory calculations. A centrosymmetric compound donor-acceptor-donor-type compound 1f with two TPE moieties proved to be the most promising multifunctional material, it exhibited tri-colored (489–569 nm) fluorescence characteristics in tetrahydrofuran-H₂O solution with a different water fraction and intense tri-colored solvatochromic (blue, green, and yellow) behaviors. These compounds could be applied as promising acid-base gas probe based on their evident color switch. Compounds 1a - 1f showed the advantage of being a potential piezochromic material.