2D Cu(I) and 3D mixed-valence Cu(I)/Cu(II) coordination polymers: Synthesis and structural characterization of [CuCl(pyz-H) 2]·2H 2O and [Cu 2Cl 2(pyz)(H 2O)]·H 2O (pyz-H = pyrazinic acid)

Abstract

Two new coordination polymers of copper(I) chloride and pyrazinic acid (pyz-H), namely [CuCl(pyz-H) 2]·2H 2O ( 1) and [Cu 2Cl 2(pyz)(H 2O)]·H 2O ( 2) have been prepared and characterized by spectroscopic, magnetic and crystallographic methods. The overall physical measurements suggest that 1 is diamagnetic and contains monodentate N-pyrazinic acid, whereas 2 is paramagnetic and contains tridentate N, N′, O- chelating bridging pyrazinato anion. In the structure of 1 as elucidated by X-ray single crystal analysis, the asymmetric units [CuCl(pyz) 2] are linked together forming a zigzag chain with tetrahedral copper(I) environment. The two lattice water molecules form hydrogen bonds with the uncoordinated N atom and carboxylate group O atom of pyz-H molecules. The Cu–N bond lengths are 2.009(6) Å and Cu–Cl distances are 2.337(2) Å. Complex 2 has a three-dimensional structure with the chains [Cu(I)Cu(II)(C 5H 3N 2O 2)Cl 2(H 2O)] interconnected by [Cu(I)Cl 2N] tetrahedral unit and [Cu(II)NO 2Cl 2] polyhedra. The Cu(I)–Cl and Cu(I)–N distances are 2.327(2)–2.581(2) Å and 1.988(6) Å, respectively, whereas the Cu(II)–Cl and Cu(II)–N bond lengths are 2.258(2), 2.581(2) Å, and 2.017(6) Å, respectively. Hydrogen bonds of the type O–H⋯O are formed between lattice and coordinated water, and carboxylate oxygens of pyrazinato ligand giving rise to a three-dimensional network. The Cl − anions act as bridging ligands in both complexes. The magnetic data of complex 2 have been measured from 2 to 300 K and discussed.