Crystal structure, Hirshfeld surface analysis and theoretical calculations of an oxalato-bridged copper(II) complex: μ-oxalato-bis[(2,2’-bipyridine) hydrate copper(II) nitrate]

The copper complex [Cu2(Bipy)2(H2O)2(C2O4)(NO3)2] (Bipy = 2,2′-bipyridine; C2O42− = oxalate) has been synthesized and characterized by single-crystal X-ray diffraction and FTIR spectroscopy. The structure determination revealed that the title compound contains centrosymmetric doubly charged dinuclear oxalato-bridged copper(II) complex cations, nitrate counter ions and water molecules. In this complex, the oxalate ligand is coordinated in a bis-bidentate bridging mode to the copper atoms. Each Cu(II) atom has a distorted tetragonal–bipyramidal environment, being coordinated by two N atoms of a chelating 2,2′-bipyridine ligand and two O atoms of the doubly deprotonated oxalate anion. Pairs of monodentate nitrate anions and aqua ligands are linked to the metallic cations in an axial position. The H-bonds occurring in the crystal structure result in the formation of 2D supramolecular chains and 3D networks. The Hirshfeld surface analysis of the complex has shown the presence of strong O–H…O and C–H…O hydrogen bonds together with non-classical weak C–H…π, π…π, π…lp/lp…π and lp …lp interactions. Furthermore, the theoretical calculations results are in agreement with the experimental geometric parameters. The NMR spectra and the MEP maps were also calculated.