Research On The Vapor- And Mechanical-Grinding-Triggered Color And Luminescene Switches Based On Platinum(Ⅱ)-alkynyl Complexes

Color and luminescence switching material means that the color and (or) luminescence of material will change under the external stimulus. These materials have important commercial value and wide application prospect on optical communication and information processing, medical treatment, military affairs, energy storage materials, environmental monitoring and many other fields due to their unique induction and recognition abilities to external signals. Now, it has become a hotspot in the field of chemistry and material chemistry. Transition metal complexes become significant research object of luminescent color-changed materials owing to its good photo- and thermal-stability, rich excited state levels, easy preparation, and tunable luminescent energy, transition metal complex become one of the significant objects in research of the luminescence switching materials.In this paper, using 4,4’-dibromo-2,2’-pyridine (diBrbpy) ligand, we designed and synthesized a intermediate, Pt(diBrbpy)Cl2, and eleven platinum(Ⅱ)-alkynyl complexes with benzene acetylene auxiliary ligands containing different substituent site and groups. The composition, structures and photophysical properties of these complexes were studied systematically by 1H NMR, IR, fluorescence spectra, UV-vis spectra, XRD, X-ray single crystal diffraction, etc. Some of them not only have vapoluminescent property or mechanoluminescent property, but also exist vapor-and mechanical-triggered dual-stimulus luminescence switching properties. The mechanism of luminescent color-changed materials is the changes of molecular stacking patterns caused by external stimulus which lead to interconversion of the lowest excited states between MLCT/LLCT and MMLCT/LLCT, and the π-π and hydrogen interactions variation in stacking structures affect on the emission energy of complexes.Furthermore, we also found that the number changes of solvate molecules can also cause the vapoluminescence phenomenon. Emission energy of the complex could decreased significantly and red-shift to near-infrared region by formation of one-dimensional metal-chain structure. The electron donating or withdrawing ability of substituted groups, the space volume and site of substituent groups can also affect the luminescence switching properties of complexes.