Construction of Highly Emissive Pt(II) Metallacycles upon Irradiation

Abstract

Summary of main observation and conclusionPhotoswitchable 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 (ΦF = 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.