Tetraphenylethene-Containing Alkynone Derivatives: Design and Synthesis, Aggregation-Induced Emission Characteristics, and the Selective Fluorescence Detection of Pd2+

Organic luminescent materials with aggregation-induced emission (AIE) characteristics have attracted much attention among the scientists in the fields of optoelectronic devices and fluorescence biotechnology. ATE materials overcomes the aggregation-caused quenching problem of traditional organic fluorescent compounds, which possess high fluorescence quantum efficiency in the aggregated states. Thanks to the great research effort of worldwide scientists, a large variety of AIE materials have been developed and the underlying mechanism has been rapidly explored. The deep understanding of the structure-property relationship of AIE compounds is still in an urgent demand for the design of new materials. In this work, based on the classical propeller-shaped AIEgen, tetraphenylethene (TPE), we designed and synthesized a series of electron donor/acceptor-containing alkynone derivatives with AIE feature such as cyano, nitro, butyl and butoxyl groups-substituted alkynone derivatives. Their chemical structures have been fully characterized by H-1 NMR, C-13 NMR, IR, and HRMS spectra, providing satisfactory analysis results. Their photophysical properties are systematically studied and the effect of substitution groups on the emission maximum, emission efficiency, as well as AIR property are discussed, respectively. Their emission maxima are located at 511 similar to 565 nm with the fluorescence quantum yields of up to 31% in the aggregated states in THF/water mixtures with high water content. The fluorescence intensity of the unsubstituted TPE-containing alkynone derivative in THF/H2O with phi(w)=90% water content is 157 times higher than that in THE solution. It is suggested that both electron-donating and electron-withdrawing substitution groups on the terminal phenyl ring decrease the emission efficiency of the the aggregated state and the introduction of nitro group dramatically quenches the emission while redshifts the emission maximum. Most importantly, the alkynone groups in these compounds can selectively coordinate with Pd2+ among a large variety of metal ions, which quench the emission of the nanoaggregates and possess high sensitivity towards Pd2+, demonstrating the potential application as an efficient Pd2+ fluorescent sensor.