Crystal structures of [Cu2(2,2′-bipyridine-N,N′)2(H2O)2(μ2-OH)2](barbiturate)2·2H2O and [Cu(2,2′-bipyridine-N,N′)(H2O)(barbiturate-O)Cl]·2H2O

Abstract

Two mixed-ligand Cu(II) complexes [Cu2(Bipy)2(H2O)2(OH)2](Hba)2·2H2O (1) and [Cu(Bipy)(H2O)(Hba)Cl]·2H2O (2) (Bipy = 2,2′-bipyridine and Hba− = barbiturate anion) were synthesized and structurally characterized by single crystal X-ray diffraction. In 1, structural data revealed distorted square-pyramidal geometry for each of two crystallographic independent copper(II) atom with the basal plane formed by two nitrogen atoms of the 2,2′-bipyridine ligand and two oxygen atoms of bridging hydroxo groups. The apical positions are filled by the oxygen atoms from a water molecule. In 2, the Cu atom is also in distorted square pyramidal geometry, where the equatorial sites are occupied by two N atoms of one Bipy ligand, one O atom of the barbiturate ion and one chloride ion and the apical position by one aqua ligand. Numerous intermolecular hydrogen bonds OH⋯O, NH⋯O, CH⋯O in the structures 1–2 and in addition OH⋯Cl, CH⋯Cl in the structure 2 form the 3D networks. Topological analysis showed that these H-bonded networks are new. An additional factor that plays a role in the crystal packing of the discussed complexes is the π-π stacking interaction between the aromatic rings of Hba− and Bipy forming infinite chains –Hba–Bipy–Bipy–Hba–. The spectroscopic and thermal properties of compounds were analyzed.