Spectral and structural characterization of copper(I) halide, nitrate and perchlorate complexes of pyrazine carboxamide (pyza) and X-ray crystal structure of polymeric [Cu(pyza)(2)I](n) complex

Copper(I) salts form with pyrazine carboxamide (pyza) complexes of the type Cu (pyza)(2)X for X = Cl, Br, I, NO3 and ClO4, Cu-2(pyza) X-3(2) for X = C l and Br, Cu(pyza)X for X = Cl, Br and I, and Cu(pyza)I . H2O. The complexe s were characterized by elemental analysis and infrared, Raman and electron spectroscopy. The overall physical measurements suggest that pyza behaves as a monodentate ligand in all complexes, except the 1:1 bromide which cont ains N-, and N,O-pyza molecules, whereas the halide, nitrate and perchlorat e complexes behave as bridging ligands giving rise to polymeric structures. The structural determination of Cu(pyza)(2)I reveals that the Cu and I ato ms are arranged alternately to form a polymeric zigzag chain with an approx imately tetrahedral copper(I) environment. These chains are connected via h ydrogen bonds of the type N-H ... O between two pyza molecules to form two- dimensional systems. The bromide and iodide complexes of all types display visible emission in the 640-675 nm region when irradiated in the UV, wherea s the other complexes do not fluoresce at room temperature. (C) 2000 Elsevi er Science Ltd All rights reserved.