STRUCTURE AND LUMINESCENCE PROPERTIES OF -DIMETHYL-1,10-PHENANTHROLINE)(CO)(3)PY](-MATRIX() IN A SOLID)

The low-temperature luminescence properties of [Re(4,7-Me(2)phen)(CO)( 3)py](+) (4,7-Me(2)phen = 4,7-dimethyl-1,10-phenanthroline, py = pyrid ine) as a crystal or in ethanol-methanol glass are reported, together with a crystal structure of the complex as its perchlorate salt. The c omplex [Re(4,7-Me(2)phen)(CO)(3)py](ClO4) crystallizes in the space gr oup Pna2(1) with a = 16.262(4) Angstrom, b = 12.721(3) Angstrom, c = 1 0.814(2) Angstrom, and Z = 4. The geometry is facial and the Re-N(4,7- Me(2)phen) bond lengths are 2.13(2) and 2.24(2) Angstrom, the Re-N(py) bond distance is 2.15(2) Angstrom, and the Re-C(CO) bond distances ar e 1.93(3), 1.87(3), and 1.90(2) Angstrom. Single-crystal absorption an d luminescence spectra at temperatures below 6 K show that the emittin g state in this environment is triplet ligand-centered ((3)LC). In an ethanol-methanol glass, the luminescence spectra indicate that a large ly (3)LC assignment is also appropriate in this matrix; however lifeti me measurements provide some evidence for a contribution from the near by triplet metal-to-Ligand charge-transfer ((3)MLCT) state. Measuremen ts of the Zeeman effect in both environments confirm these conclusions .