LAUSR

Abstract A polynuclear Cu(II) coordination system of {[Cu(ox)(NA)]. H2O}n (1), where ox = oxalate and NA = nicotinamide, and a mononuclear compound [Cu(NA)2(NO3)2(H2O)2] (2) were synthesized and characterized by single-crystal X-ray diffraction (1), IR, UV–VIS and EPR spectra, magnetic measurements and elemental analysis. In both complexes, Cu(II) adopts a distorted octahedral geometry. In 1 each copper center is coordinated to two oxalate units: one in a bis (bidentate) chelating mode linking two metal ions from the same plane, while the other, through a µ4 pattern, linking copper ions from adjacent positions. The sixth coordination position of each copper ion is occupied by the pyridinic nitrogen of a nicotinamide molecule. In 2 the Cu(II) basal plane consists of the oxygen atoms of the water molecules and the nitrogen atoms of nicotinamide molecules. The axial positions are occupied by oxygen atoms of the two nitrate groups, which are monodentate. The magnetic measurements for the polynuclear complex show antiferromagnetic coupling, the electronic structure modeling completing the insight to orbital factors of the spin interaction. Graphical abstract