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

Complexes of Ni^II with new ligands N′,N′′-bis(3-carboxy-1-oxoprop-2-enyl), 2-Amino-N-arylbenzamidine (C₂₁H₁₇N₃O₆), N′,N′′-bis(3-carboxy-1-oxopropanyl) 2-Amino-N-arylbenzamidine (C₂₁H₂₁N₃O₆) and N′,N′′-bis(3-carboxy-1- oxophenelenyl) 2-Amino-N-arylbenzamidine (C₂₉H₂₁N₃O₆) 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 MO₆ weak field octahedral chromophore. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for Ni^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: C₂₁H₁₉N₃O₈ Ni is orthorhombic, space group P_mmm, a = b = 9.015360(Å), c = 10.554430(Å), V = 572.11A³; C₂₁H₂₃N₃O₈Ni is monoclinic, space group P_2/m, a = 15.08206(Å), b = 5.358276(Å), c = 9.898351(Å), V = 671.58A³; C₂₉H₂₃N₃O₈Ni is tetragonal, space group P_4/m, a = b = 6.328104(Å), c = 9.82213(Å), V = 393.33A³. Molecular structures of the complexes have been optimized by MM2 calculations and supported octahedral arrangements around Nickel(II) ions.