Utilization of metal complexes formed by copper(II) acetate or nitrate, for the urea assay

The concentration level of urea in the tear fluid is a diagnostic biomarker for the detection of the dry eye syndrome (DES). Two complexes of Cu(II) with urea with the formulae Cu2(CH3COO)4U2 (1) and Cu(NO3)2U4 (2), (U = urea) were synthesized and characterized. Complexes 1 and 2 were used for the qualitative analysis of urea. [Display omitted] •Copper(II) Urea complexes.•Structural characterization.•Urea assay.•Dry eye syndrome. Two Cu(II) complexes with urea with formulae Cu2(CH3COO)4U2 (1) and Cu(NO3)2U4 (2), (U = urea) were synthesized and characterized by melting point (m.p.), elemental analysis (e.a.), magnetic susceptibility measurements, Thermal Analysis Thermogravimetry (TG/DTA) and Differential Scanning Calorimetry (DSC) and spectroscopic techniques (Fourier Transform Infra Red (FTIR) and Ultra Violet-Visible (UV–Vis)). The crystal structures of 1–2 were determined by single crystal X-ray diffraction analysis. Complex 1 is di-nuclear. Four oxygen atoms from the four bridging acetates and one from a terminal urea form a square pyramidal geometry around each metal. The short copper–copper bond distance of 2.6134(9) Ǻ, in the case of 1, implies d–d interaction between metal centers (cuprophilicity). Intra-molecular hydrogen bonding interactions lead to a polymeric 3D network, forming pores with dimensions 4.549 × 6.723 Å. Two oxygen atoms from nitrate groups and four oxygen atoms from urea form an octahedron around copper(II) ion in case of 2. Complexes 1 and 2 were used for the indirect determination of urea by Thin Layer Chromatography (TLC) densitometry.