Structural characterization and emission properties of mixed-ligand transition metal coordination complexes with dicarboxylic acids and pyrazinecarboxamide

Abstract Five new transition metal coordination compounds based on pyrazinecarboxamide and dicarboxylic acids have been prepared, and their structures have been characterized by IR spectroscopy and single crystal X-ray diffraction. The crystalline solids include one dinuclear compound [Cu2(mal)2(pca)2(H2O)2]·H2O (1), three one-dimensional coordination polymers [M(mal)(pca)(H2O)]n M = Co(II), Zn(II) (2, 3), [Cu2(CH3COO)4(pca)]n (4) and one two-dimensional coordination polymer [Cd(bdc)(pca)(H2O)]n (5), where pca = pyrazinecarboxamide, H2mal = malonic acid and H2bdc = 1,4-benzenedicarboxylic acid. The pca coordinates to the metal centers as a neutral ligand in chelating (1, 2, 3), bidentate bridging (4) and monodentate modes (5), while the bidentate acetate, malonate and benzenedicarboxylato anionic ligands provide extensions of structures. The new compounds 1, 3 and 5 reveal violet and ultraviolet luminescence upon excitation with ultraviolet light.