A series of Cu(I) complexes formulated as [Cu(2)(mu-X)(2)(PPh(3))(L)(n)] were prepared with various mono- and bidentate N-heteroaromatic ligands (X = Br, I; L = 4,4'-bipyridine, pyrazine, pyrimidine, 1,5-naphthyridine, 1,6-naphthyridine, quinazoline, N,N-dimethyl-4-aminopyridine, 3-benzoylpyridine, 4-benzoylpyridine; n = 1, 2). Single-crystal structure analyses revealed that all the complexes have planar {Cu(2)X(2)} units. Whereas those with monodentate N-heteroaromatic ligands afforded discrete dinuclear complexes, bidentate ligands formed infinite chain complexes with the ligands bridging the dimeric units. The long Cu...Cu distances (2.872-3.303 A) observed in these complexes indicated no substantial interaction between the two Cu(I) ions. The complexes showed strong emission at room temperature as well as at 80 K in the solid state. The emission spectra and lifetimes in the microsecond range were measured at room temperature and at 80 K. The emissions of the complexes varied from red to blue by the systematic selection of the N-heteroaromatic ligands (lambda(em)(max): 450 nm (L = N,N-dimethyl-4-aminopyridine) to 707 nm (L = pyrazine)), and were assigned to metal-to-ligand charge-transfer (MLCT) excited states with some mixing of the halide-to-ligand (XL) CT characters. The emission energies were successfully correlated with the reduction potentials of the coordinated N-heteroaromatic ligands, which were estimated by applying a simple modification based on the calculated stabilization energies of the ligands by protonation.

New dinuclear copper(I) complexes [Cu2(micro-X)2(micro-1,8-naphthyridine)(PPh3)2] (X=I, Br) having the butterfly-shaped {Cu2(micro-X)2} unit show red phosphorescence at room temperature in the solid state. Molecular orbital calculations show that the emissions of the new complexes are not directly related to their short Cu...Cu separations [2.6123(5) and 2.6271(4) A] and are assignable to the triplet charge-transfer excited states from the {Cu2(micro-X)2} core to 1,8-naphthyridine.

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The metal-induced regulation of fullerene complexation with double-calix[5]arene is described. The receptor shows strong binding to C70 only in the presence of Cu+.

A new class of fullerene sensors based on calix[5]arenes has produced the highly sensitive detection of C60 and C70.