摘要
Photoswitchable or photoactivatable fluorescent species have been found wide applications within supramolecular chemistry and materials science.In this study,we successfully constructed two highly emissive Pt(Ⅱ)metallacycles from the diarylethene ligands via coordination-driven self-assembly.Different from the most known fluorescent metallacycles,the obtained metallacycles have displayed"turn-on"fluorescence switching.They are non-fluorescent in solution,but they emit highly yellow or orange fluorescence under ultraviolet irradiation.The metallacycles were well characterized by 1H NMR,31P NMR and ESI-TOF-MS.The photochromic properties of the resultant metallacycles were investigated by 1H NMR,31P NMR,UV/Vis spectrum and fluorescence spectrum.Notably,NMR studies revealed that these two metallacycles featured excellent cyclization efficiency(90% conversion efficiency).Moreover,the closed-ring isomers of the metallacycles displayed relatively high quantum yield(ФF=0.5).DFT simulations demonstrated that the antiparallel configuration of the diarylethene ligand had an angle closed to 120°,which was more stable in energy compared to the parallel configuration,thus allowing for the facile construction of highly emissive metallacycles.We believe that such highly emissive metallacycles which are in-situ prepared upon irradiation can be used as new fluorescence materials for sensing and bioimaging in the future.
