The synthesis and crystal structure of a new copper(I) polymer, [{(Ph3P)2Cu2(μ-Cl)2(μ-pyrazine)}∞], are reported. The polymer is photoluminescent with its emission maximum at 16 340 cm-1 at a temperature of 20 K. The emitting state is assigned with the assistance of excited state distortions determined by using resonance Raman intensities. The polymer consists of (PPh3)(pyz)Cu(μ-Cl2)Cu(pyz)(PPh3) units in which pyrazine ligands bridge copper pairs to form a chain of dimers. The packing arrangement contains two inversion centers. Each dimer has an inversion center between the two coppers and the bridging chlorine atoms. A second inversion center is located in the center of the pyrazine ligand, which links the dimers in an infinite linear chain. The nitrogen atom of the pyrazine, the phosphorus atom of one triphenylphosphine, and the two chlorine atoms form a slightly distorted tetrahedron about the copper. The largest distortions in the lowest excited electronic state, determined from the resonance Raman intensities, occur along totally symmetric modes of the pyrazine ligand. The emission is assigned to copper(I) to pyrazine charge transfer.

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The low-temperature luminescence spectra of tetrameric mixed-metal clusters of the type (DENC)3Cu3M(NS)Cl4 and (DENC)3CuI2CuIICo(NS)2Cl4 (DENC = iV.A-diethylnicotinamide; NS™ = S'-methylhydrazinecarbodithioate Schiff base; and M = Co(ll), Ni(II), Cu(II), or Zn(II)) in anhydrous methylene chloride are reported. The parent cluster containing four Cu(I) atoms emits at 15 100 cm™1. The clusters containing three Cu(I) atoms and a fourth first-row transition metal emit at Xmax = 13 500 cm™1 for M = Co(II), Xmax = 14000 cm™1 for M = Ni(II), Xmax = 13 150 cm™1 for M = Cu(II), and Xmax = 15000 cm™1 for M = Zn(II). The cluster containing two Cu1, one Cu11, and one Co11 emits at 13 300 cm™1. The emission from all of the clusters is centered on the coppers (not on the ligands or the other metals) and is related to the 3d94s* excited state strongly modified by copper-copper interactions. The presence of the other metals only slightly perturbs the energy of the emission centered on the coppers. In the case of the mixed-metal clusters containing Co(II) and Cu(II) metals in the core, the emission is not from the lowest excited state of the cluster. In these cases ligand field states centered on the M(II) are lower in energy than the Cu(I) centered emitting state. The emission lifetimes are shortest for the clusters with low-lying d-d excited states.

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