Synthesis and Photoluminescence of Tetracyanidonitridorhenium(V) Complexes with Five-Membered N-Heteroaromatic Ligands and Photoluminescence-Intensity Change.

Novel tetracyanidonitridorhenium(V) complexes with five-membered N-heteroaromatic ligands, (PPh)[ReN(CN)L] [L = imidazole (Him) (), 1-methylimidazole (Mim) (), and pyrazole (pyz) ()] and (PPh)[ReN(CN)L]·L [L = Him () and Mim ()], were synthesized by the reactions of (PPh)[ReN(CN)] () with Him, Mim, and pyz, and their structures were determined by single-crystal X-ray analysis. The complexes , , , and showed intense photoluminescence, with the emission quantum yields (Φ) being 0.65-0.75 in the solid state at 296 K. In contrast, the Φ and τ values of are significantly smaller and shorter, respectively, than the relevant values of . The interconversion reactions among , , and accompanied by large photoluminescence-intensity changes were accomplished by solvent-free reactions and exposure of water. The mechanochemical reaction of with 1 mol equiv of Him in the solid state gave . Complex was also obtained by the mechanochemical reaction of with 2 mol equivalents of Him in the solid state. By placing solid of in water, the solid showed intense photoluminescence to give . Complex was produced under vacuum at 185 °C from or .