Synthesis and characterization of mono- and dinuclear copper(I) complexes with 3-(2-pyrimidinyl)-1,2,4-triazine

The mono- and dinuclear Cu(I) complexes [CuI(PPh3)(pmtz)] (1) and [{Cu(PPh3)2}2(μ-pmtz)](ClO4)2 (2), where pmtz is 3-(2-pyrimidinyl)-1,2,4-triazine, have been synthesized and characterized. Single-crystal X-ray diffraction analysis reveals that the pmtz acts as a bidentate ligand in complex 1, whereas in complex 2 the pmtz coordinates as a bis-bidentate chelate, assembling two identical {Cu(PPh3)2} moieties into a copper(I) dimer with a triple-decker sandwich structure involving phenyl/pmtz/phenyl π–π interactions. The UV–vis spectra of complexes 1 and 2 show low-energy absorptions at 350–550 nm, assigned to the Cu(I) to pmtz MLCT transition, probably mixed with some XLCT character for 1. The absorption of 2 is blue-shifted relative to that of 1 due to the substitution of the iodide of 1 with the π-acceptor ligand PPh3. Complexes 1 and 2 are non-emissive, both in solution and in the solid state, most likely owing to the electronic effects induced by the additional nitrogen donor of pmtz compared to 2,2′-bipyrimidine.