Structural, spectroscopic and thermal characterization of 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester and its Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO 2(II) complexes

Abstract

Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO 2(II) complexes with the ligand 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester (HL 2) have been prepared and characterized by elemental analyses, molar conductance, magnetic moment, thermal analysis and spectral data. 1:1 M:HL 2 complexes, with the general formula [M(HL 2)X 2]· nH 2O (where M = Co(II) (X = Cl, n = 0), Ni(II) (X = Cl, n = 3), Cu(II) (grey colour, X = AcO, n = 1), Cu(II) (yellow colour, X = Cl, n = 0) and Zn(II) (X = Br, n = 0). In addition, the Fe(III) and UO 2(II) complexes of the type 1:2 M:HL 2 and with the formulae [Fe(L 2) 2]Cl and [UO 2(HL 2) 2](NO 3) 2 are prepared. From the IR data, it is seen that HL 2 ligand behaves as a terdentate ligand coordinated to the metal ions via the pyridyl N, carboxylate O and protonated NH group; except the Fe(III) complex, it coordinates via the deprotonated NH group. This is supported by the molar conductance data, which show that all the complexes are non-electrolytes, while the Fe(III) and UO 2(II) complexes are 1:1 electrolytes. IR and H 1 -NMR spectral studies suggest a similar behaviour of the Zn(II) complex in solid and solution states. From the solid reflectance spectral data and magnetic moment measurements, the complexes have a trigonal bipyramidal (Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (Fe(III), UO 2(II) complexes) geometrical structures. The thermal behaviour of the complexes is studied and the different dynamic parameters are calculated applying Coats–Redfern equation.