Hydrogen-bonded supramolecular structures in copper(II) nitrobenzoates with N-methylnicotinamide: synthesis, supramolecular structure, Hirshfeld surface analysis, spectral and DFT study

The synthesis of six new copper(II) nitrobenzoate complexes with N-methylnicotinamide, used as an auxiliary ligand for a supramolecular interaction study, is reported. Crystal structures of six novel compounds [Cu(2-NO2bz)2(mna)2(H2O)2] (1), [Cu(2-NO2bz)2(mna)2(H2O)2]∙2H2O (2), [Cu(3-NO2bz)2(mna)2(H2O)2] (3), [Cu(3,5-(NO2)2bz)2(mna)2(H2O)2]∙2H2O (4), [Cu(4-NO2bz)2(mna)2(H2O)2]∙2(4-NO2bzH) (5) and [Cu(3,5-(NO2)2bz)2(mna)(H2O)3] (6) (mna = N-methylnicotinamide, 2-NO2bz = 2-nitrobenzoate, 3-NO2bz = 3-nitrobenzoate, 4-NO2bz = 4-nitrobenzoate, 3,5-(NO2)2bz = 3,5-dinitrobenzoate) were determined by X-ray analysis. Compounds 1–6 are mononuclear with a tetragonal-bipyramidal geometry around the Cu2+ ion. The molecules of the studied complexes are mostly linked by a combination of N–H…O and O–H…O hydrogen bonds between N-methylnicotinamide and water molecules into supramolecular hydrogen-bonded coordination chains and networks. Intermolecular interactions in the supramolecular structures were also studied using Hirshfeld surface analysis. In addition, the complexes 1–6 have been characterised by elemental analysis, IR, UV–Vis and EPR spectroscopy. Density functional theory calculations were performed in order to reproduce the EPR magnetic parameters. DFT calculations of the EPR parameters show a good agreement with the experimental results.