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.