Study of copper(II) thiophenecarboxylate complexes with nicotinamide

The synthesis and characterization of [Cu(3-Me-2-tpc)2(nia)2] (1), [Cu(5-Me-2-tpc)2(nia)2] (2), [Cu(2-tpc)2(nia)2] (3) and [Cu(5-Me-2-tpc)2(nia)2(H2O)] (4) (where 2-tpc is 2-thiophenecarboxylate, 3-Me-2-tpc is 3-methyl-2-thiophenecarboxylate, 5-Me-2-tpc is 5-methyl-2-thiophenecarboxylate and nia is nicotinamide) are reported. The complexes under study were characterized by electronic, IR, EPR spectroscopy, magnetic susceptibility over the temperature range and X-ray structure analysis. The coordination arrangement around each copper(II) atom is a distorted tetragonal bipyramidal. The discrepancies between two Cu–O axial bond distances increases in the order: 0 Å (complex 1) < 0.050 Å (complex 3) < 0.209 Å (complex 2) < 0.516 Å (complex 4, Cu1) < 0.746 Å (complex 4, Cu2), indicating that in the same order a distortion of the respective tetragonal bipyramids increases. This is in a good agreement with the ligand field band position in their electronic spectra.The complex molecules of all compounds are connected through H-bonds into supramolecular chains or frameworks. Spectral and magnetic behaviours are discussed with regard to X-ray parameters. Small negative value of Weiss constants confirm an existence of a very weak antiferromagnetic interaction between Cu(II) magnetic center in the crystal lattice.The EPR parameters are typical for a tetragonal bipyramidal Cu(II) complexes. The gav values at r.t. are somewhat lower than those at 77 K.

Four copper(II) 2-thiophenecarboxylate complexes with nicotinamide have been synthesized. The complexes are structurally characterized through single crystal X-ray diffraction. The spectral and magnetic properties of all complexes have also been studied.Figure optionsDownload as PowerPoint slide