Study of copper(II) thiophenecarboxylate complexes with N-methylnicotinamide

The synthesis and spectral characterization of four new complexes [Cu2(5-Me-2-tpc)4(N-Menia)2] (1), [Cu(5-Me-2-tpc)2(N-Menia)2(H2O)2] (2), [Cu(3-Me-2-tpc)2(N-Menia)2]·H2O (3), and [Cu2(2-tpc)4(N-Menia)]n (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 N-Menia is N-methylnicotinamide) with various structural types is reported and their X-ray structures were determined. The complex molecules of 1–3 are connected through hydrogen bonds into 2D networks. On the other hand, the compound 4 forms 1D zigzag coordination polymer. Electronic, IR, EPR spectra and magnetic susceptibility over the temperature range 1.8–300 K are discussed in terms of known crystal and molecular structure. The carboxyl group of the thiophenecarboxylate anions coordinates to the Cu(II) atom as a unidentate (complex 2) or as a bidentate bridging (complexes 1 and 4) as well as bidentate chelating (complex 3) ligand. Based on the IR spectra it can be concluded that hydrogen bonds strongly influence the position and the shape of the stretch vibrations bands assigned to NH and amide carboxyl group CO. EPR spectra and magnetic properties of the complexes 2 and 3 exhibit the magnetism which is typical for isolated monomeric Cu(II) ions and in case of the complexes 1 and 4 as dimeric exchange-coupled copper(II) pairs.

[Cu2(2-thiophenecarboxylate)4(N-methylnicotinamide)]n – first example of 1D zigzag polymeric complex with N-methylnicotinamide.Figure optionsDownload as PowerPoint slide