Photoluminescence Switching with Changes in the Coordination Number and Coordinating Volatile Organic Compounds in Tetracyanidonitridorhenium(V) and -technetium(V) Complexes

Six-coordinate distorted octahedral tetracyanidonitridorhenium­(V) and -technetium­(V) complexes with a volatile organic compound (VOC) coordinating at the trans position of a nitrido ligand, (PPh4)2[MN­(CN)4L] (M = Re, L = MeOH, EtOH, acetone, or MeCN; M = Tc, L = MeOH), and five-coordinate square-pyramidal tetracyanidonitrido complexes without an axial ligand, (PPh4)2[MN­(CN)4] (M = Re or Tc), were synthesized and characterized. Single-crystal X-ray structural analysis was carried out for (PPh4)2[MN­(CN)4L] (M = Re, L = MeOH, EtOH, or acetone; M = Tc, L = MeOH) and (PPh4)2[ReN­(CN)4]. All complexes studied showed photoluminescence in the solid state at room temperature. Reversible luminescence switching between six- and five-coordinate rhenium­(V) complexes and between the relevant six-coordinate rhenium­(V) complexes except that between the MeCN and acetone complexes was achieved by exposing them to VOC vapor in the solid state at room temperature. Luminescence changes were observed from the five-coordinate technetium­(V) complexes in a MeOH vapor atmosphere in the solid state. In contrast, no vapochromic luminescence was observed from the five- and six-coordinate complexes in an acetone vapor atmosphere.