Syntheses, structures and magnetisms of copper(II)-azido coordination compounds with p-substituted benzoates as coligands

Employing p-substituted benzoates with electron-withdrawing/electron-donating groups as coligands, four copper–azido compounds, [Cu1.5(p-NO₂-benzoate)(N3)2(H₂O)]n (1), [Cu(p-NO₂-benzoate)(N3)(H₂O)]n (2), [Cu(p-OH-benzoate)(N3)(H₂O)]n·nH2O (3) and [Cu(p-CH3-benzoate)(N3)]n (4), have been hydrothermally synthesized and structurally charactierized by single crystal X-ray diffraction. Structural analysis reveals that all compounds are composed of mixed EO-azido and syn–syn carboxylato-bridged Cu-N3/COO chains. Compound 1 features the alternating triple-bridged (μ-EO-N3)(μ-COO)(μ-H₂O) and the double-bridged (EO-N3)2 modes. Both of 2 and 3 display the triple-bridged fashion (μ-EO-N3)(μ-COO)(μ-H₂O). While 4 exhibits the double-bridged mode (μ-EO-N3)(μ-COO). Based on hydrogen-bonding interactions, Cu–N3/COO chains in 1–3 are further connected to form 3D supramolecular frameworks. As for compound 4, there are not hydrogen-bonding interactions when the p-CH3 substituted benzoate is employed as coligand. These compounds show intrachain ferromagnetic performance and different bulk properties. Remarkably, 1 features metamagnetism from antiferromagnetism to ferrimagnetism, while 3 reveals long-range ferromagnetic ordering between Cu(II) ions. Magneto-structural correlation has been also investigated.