A series of Cu(I) mixed-ligand complexes containing dmp (2,9-dimethyl-1,10-phenanthroline) and one of simple diphosphine ligands (Ph2P(CH2)nPPh2) were prepared. Among the complexes, [Cu(dppp)(dmp)]PF6 (n=3) and [Cu2(dppb)2(dmp)2](PF6)2 (n=4) were characterized by X-ray structure analyses. The dppp complex has been characterized as a mononuclear complex, while [Cu2(dppb)2(dmp)2]2+ exists as a dinuclear complex in which two dppb ligands bridge between the two Cu(I) atoms. Although the distorted tetrahedral structures around the central metals of the two complexes are similar, the P-Cu-P angles are different between the two complexes. All of the series of complexes show photoluminescence in solution, and the intensity of the luminescence increases with n (n=2-4). The non-radiative rate constants of the complexes decrease markedly with n although radiative rate constants of the complexes are similar.

The Ag(I) complex with o-bis(diphenylphosphino)benzene shows reversible interconversion between blue-emitting (1b) and green-emitting (1g) materials on grinding and heating; comparison of the structure of 1b with another green-emitting crystals (2) having the same formula suggests the chromism results from intermolecular interactions between adjacent phenylene rings.

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A series of copper(I) complexes bearing 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmpp) and a diphosphine ligand have been prepared. The diphosphine ligands used have two, three or four methylene carbons between the two phosphorus atoms. The crystallographic study has revealed that two of the three complexes have the mononuclear structure bearing dmpp and a bidentate diphosphine ligand, and one is a diphosphine-bridged binuclear complex. The photoluminescence of the complexes in solution was studied and compared with the previously reported complexes bearing 2,9-dimethyl-1,10-phenanthroline (dmp). It was found that the two phenyl groups on the phenanthroline ligand have a marked effect on the photophysical properties of the complexes; the intensity of the emission of the complexes is greatly enhanced by the phenyl groups. The photophysics of the complexes is discussed with the results of DFT and TDDFT calculations.

The structural and spectroscopic properties of a Cu(I) complex bearing a methylene-linked bis(N-heterocyclic carbene) ligand, [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) were investigated. X-ray single crystal structure analysis revealed that the complex is binuclear similar to the corresponding silver(I) complex. In [Cu(2)(mu-Me-mbim)(2)](PF(6))(2), cation-pi interaction between copper and the adjacent carbene carbon is observed. On the other hand, the copper-copper interaction is very weak in the crystal and almost negligible in solution. The absorption spectrum of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) in methanol shows a strong absorption band (epsilon = 23 000 dm(3) mol(-1) cm(-1)) and a weaker shoulder (epsilon = 6200 dm(3) mol(-1) cm(-1)) at 261 nm and 300 nm, respectively. From molecular orbital calculations using TD-DFT, these absorption bands are assigned to the metal-centered transitions with some contribution from the NHC orbitals. The powdered sample of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) shows bright blue-green phosphorescence with a high quantum yield (43%). The phosphorescence is of dual-emission character at room temperature with peak maxima at 374 nm and 482 nm whereas it changes to a single emission band centered around 500 nm at 77 K. Molecular orbital calculations indicate that the luminescence derives from the triplet MC and MLCT mixed excited states. A methanolic solution of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) shows yellow-green phosphorescence with a peak maximum at 542 nm. Unlike in the solid state, no dual-emission was observed. These results suggest that the dual emission is caused by differences in the contribution of metal-metal interactions at room temperature in the solid state. The differences in the absorption and emission properties between [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) and the related Cu(I)-diphosphine complex, [Cu(2)(mu-dcpm)(2)](BF(4))(2) are discussed.