Novel method for the production of copper(II) formates, their thermal, spectral and magnetic properties

Article abstract of DOI:10.1016/j.jallcom.2020.156208

A new method for the synthesis of various types of copper(II) formates with Cu(NO₃)₂?3H₂O and formic acid, orthorhombic (α) and monoclinic (β) modifications of anhydrous copper(II) formate, as well as Cu(HCOO)₂?2H₂O and Cu(HCOO)₂?4H₂O. The identity of the obtained compounds was confirmed by X-ray phase analysis, optical microscopy and thermogravimetry methods. It was shown that Cu(HCOO)₂?4H₂O can be used as a precursor for producing copper powders with particle size of the order of 150 nm. The results of investigation of vibration and absorption spectra of α and β modifications of anhydrous copper(II) formate are presented. Their magnetic behavior in the temperature interval 2–300 K was estimated, and comparative analysis of magnetic properties was carried out. First-principle calculations of electronic band structure for anhydrous α and β modifications were performed. The results obtained correspond to experimentally observed structural instability of β-Cu(HCOO)₂, fundamental absorption edge enhancement during transition from α to β modification, and low-temperature ferromagnetic ordering in α-Cu(HCOO)₂. Simulation for β modification is indicative of antiferromagnetic ordering of magnetic moments inside chains formed by copper-oxygen octahedra.