Synthesis, crystal structure, magnetism and specific heat of a new copper(II) compound with p-aminobenzoic acid

In this work we present the synthesis, crystal structure, magnetic and specific heat measurements of a new monomeric copper(II) compound, in which the metal ion is coordinated to two p-aminobenzoic acid (PABA) molecules and two chloride ions. This compound with formula [CuCl2(C7H7NO2)2] presents a peculiar crystalline structure packing, showing hydrogen-bonds between carboxylic acid groups and short N–H⋯Cl contacts resulting in a polymeric character in two dimensions. In the third direction, Cu⋯Cl close contacts between neighboring molecules are responsible for a chain-like magnetic behavior. Considering the simplicity of the molecular unit, the magnetic properties show surprising results: below 6.4 K a hysteresis cycle appears in the magnetization curves as well as a splitting between low field ZFC–FC measurements. No phase transition to a long-range order was observed by specific heat measurement.

Graphical abstractA new copper(II) complex with p-aminobenzoic acid was synthesized. In the crystalline structure, a network of H-bonds and short N–H⋯Cl contacts lead to a polymeric character in two dimensions. The magnetic properties show surprising results: below 6.4 K a hysteresis cycle appears in the magnetization curve.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Monomeric copper(II) complex with p-aminobenzoic acid. ► Short contacts N–H⋯Cl give rise to ferromagnetic interactions. ► The compound presents ZFC–FC splitting and hysteresis. ► No long range order was observed in specific heat measurement.