Nickel(II) complexes of new polydentate carboxyamide: spectroscopic, kinetics of thermal decomposition and X-ray powder diffraction studies

Complexes of Ni^sup II^ with new ligands N',N''-bis(3-carboxy-1-oxoprop-2-enyl), 2-Amino-N-arylbenzamidine (C^sub 21^H^sub 17^N^sub 3^O^sub 6^), N',N''-bis(3-carboxy-1-oxopropanyl) 2-Amino-N-arylbenzamidine (C^sub 21^H^sub 21^N^sub 3^O^sub 6^) and N',N''-bis(3-carboxy-1- oxophenelenyl) 2-Amino-N-arylbenzamidine (C^sub 29^H^sub 21^N^sub 3^O^sub 6^) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, TOF-mass spectra, magnetic susceptibility measurements, thermal studies and X-ray powder diffraction studies. Vibrational spectra indicate coordination of amide and carboxylate oxygen of the ligands along with two water molecules giving a MO^sub 6^ weak field octahedral chromophore. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for Ni^sup II^ complexes. The elemental analyses and mass spectral data have justified the ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The crystal data: C^sub 21^H^sub 19^N^sub 3^O^sub 8^ Ni is orthorhombic, space group P^sub mmm^, a = b = 9.015360(Å), c = 10.554430(Å), V = 572.11A^sup 3^; C^sub 21^H^sub 23^N^sub 3^O^sub 8^Ni is monoclinic, space group P^sub 2/m^, a = 15.08206(Å), b = 5.358276(Å), c = 9.898351(Å), V = 671.58A^sup 3^; C^sub 29^H^sub 23^N^sub 3^O^sub 8^Ni is tetragonal, space group P^sub 4/m^, a = b = 6.328104(Å), c = 9.82213(Å), V = 393.33A^sup 3^. Molecular structures of the complexes have been optimized by MM2 calculations and supported octahedral arrangements around Nickel(II) ions.[PUBLICATION ABSTRACT]