Mononuclear, dinuclear, and polynuclear bis(2-pyrimidylcarbonyl)amido copper(II) complexes: Synthesis, structure, thermal and magnetic properties

Three copper(II) complexes, namely [Cu(bpca)(NO3)(H2O)] (1), [Cu2(bpca)2(mu-C2O4)(H2O)2] (2), and [Cu (bpca)(mu-Cl)]n (3) (Hbpca 1/4 bis(2-pyrimidylcarbonyl)amine), have been synthesized using multidentate 2,4,6tris(2-pyrimidyl)-1,3,5-triazine (TPymT) and rhodizonic acid (RA) ligands. Compounds 1-3 have been characterized utilizing elemental analysis, FT-IR, Far-IR, ICP-OES, TGA, and single-crystal/powder X-ray diffraction analysis. Single-crystal X-ray analysis revealed that 1 and 2 crystallize in the monoclinic crystal system with space groups P21/n and C2/m, respectively, while 3 crystallizes in the orthorhombic crystal system with the Fdd2 space group. The thermogravimetry of the complexes supported the elemental and crystallographic results. Magnetic study clarified the presence of ferromagnetic coupling in both compounds 2 and 3. A singlet-triplet model was applied to the susceptibility data on dinuclear 2, yielding 2J/kB = +2.04 +/- 0.05 K in the H = - 2JS1. S2 convention. For polynuclear 3, a uniform ferromagnetic chain model gave 2J/kB = +5.57 +/- 0.04 K. Density functional theory (DFT) calculations using the unrestricted B3LYP and/or M06-L functionals indicated that the magnetic couplings in 2 and 3 are ferromagnetic, consistent with the superexchange coupling mechanism.