Structure of a Cu(II) Complex Based on 1,10-Phenanthroline and Benzhydroxamic Acid Ligands

Inorganic chemistry is rapidly producing novel molecules and useful materials. Mixed-ligand complexes of copper (II) ions with 1,10-phenanthroline (Phen) have been developed, and their optical and magnetic properties, stability, antibacterial activity, and crystal structures have all been comprehensively explored [1-2]. Based on these findings, Phen-containing mixed-ligand complexes were created. Their crystal structures, IR and UV-visible spectra, and how the copper ion coordinated and remained stable at high temperatures were next examined by the researchers [3].

This work synthesized a mixed-ligand complex, [Cu(C₁₂H₈N₂)(C₆H₅CONHO)·NO₃]·H₂O, from Phen and benzhydroxamic acid. The crystal structure and physicochemical characteristics were studied using UV-Vis and IR spectroscopy, thermogravimetric (TG) analysis, and Hirshfeld surface analysis.

A mixed-ligand complex was synthesized by dissolving 1 mmol of Phen 1 mmol of benzhydroxamic acid and 1 mmol of Cu(NO₃)₂·5H₂O (0.20 g) in ethanol to obtain 0.05 M solutions. The Cu(NO₃)₂ and BA solutions were first mixed, followed by dropwise addition of the Phen solution under magnetic stirring. The mixture was heated at 50 °C for 20 min and then allowed to evaporate at room temperature. After 20 days, dark-green single crystals were obtained.

The Cu(II) complex was found to possess a square-pyramidal coordination geometry. The Cu(II) ion is coordinated in the equatorial plane by two nitrogen atoms from the Phen ligand (Cu1—N1 1.986(3) Å, Cu1—N2 1.986(3) Å) and two oxygen atoms from the benzhydroxamic acid ligand (Cu1—O1 1.919(2) Å, Cu1—O2 1.920(2) Å). In the axial position, an oxygen atom from the nitrate ion is coordinated (Cu1—O4 2.580(4) Å). According to the Hirshfeld surface analysis of the complex compound, the two-dimensional fingerprint plots indicate that H···H and O···H/H···O interactions make the major contributions to the intermolecular contacts. In the UV–visible spectrum, a low-intensity absorption band corresponding to d–d transitions was observed at 634 nm.