Structure, thermal analysis and magnetism of the doubly bridged linear polymer [Ni(4-NH2-C6H4CO2)2(CH3OH)2] · CH3OH

The title compound [Ni(4-NH2-C6H4CO2)2(CH3OH)2] · CH3OH (1) consists of Ni(II) atoms doubly bridged by p-aminobenzoate ligands (PAB) into 1D chains which are further connected into a 3D framework by methanol molecules through hydrogen bonding. Compound 1 is monoclinic P2(1)/n, a = 9.0903(5) Å, b = 10.9059(5) Å, c = 9.9994(5) Å, β = 106.6880(10)°, Z = 4. Intrachain π–π interactions are observed between the aromatic rings of doubly bridging PAB ligands. The aromatic rings are in an offset arrangement with 3.607 Å interplanar spacing. The magnetic data of compound 1 for the temperature range 300–3 K is indicative of ferromagnetically coupled nickel species. The best fitting parameters were obtained for J = 0.74 cm−1, D = −2.48 cm−1 and g = 2.35. Thermogravimetric analysis of 1 indicates a sharp weight loss of one PAB ligand centered at 387.42 °C (ΔH = 94.86 kJ/mol) and a loss of two coordinated methanol molecules at 489.20 °C with ΔH = 29.78 kJ/mol. The formation constant of Ni(II) with p-aminobenzoic acid has been evaluated at different temperatures using pH titration techniques in 50% ethanol. The obtained values at 25 °C are log Kf1 = 3.24 and log Kf2 = 1.21. The thermodynamic parameters of complexation were also calculated and discussed.

The title compound [Ni(4-NH2-C6H4CO2)2(CH3OH)2] · CH3OH (1) consists of Ni(II) atoms doubly bridged by p-aminobenzoate ligands (PAB) into 1D chains which are further connected into a 3D framework by methanol molecules through hydrogen bonding. Intrachain π–π interactions are observed between the aromatic rings of doubly bridging PAB. The magnetic data of compound 1 for the temperature range 300–3 K is indicative of ferromagnetically coupled nickel species. Thermogravimetric analysis of 1 indicates a sharp weight loss of one PAB ligand and two coordinated methanol molecules. The formation constant and thermodynamic parameters of complexation of Ni(II) with p-aminobenzoic acid have been evaluated.Figure optionsDownload as PowerPoint slide