Summary
New pincer ligand, 6-hydroxymethylpyridine-2-carboxylic acid methyl ester, HL, and its bipositive, tripositive and uranyl metal complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance and 1H NMR spectra, molar conductance and magnetic moment measurements. The downfield shift of the aliphatic OH signal (from 3.87 vs. 2.96 ppm in the ligand) upon complexation indicates the coordination by protonated aliphatic OH group. Zn(II) and UO2(II) complexes are found to be diamagnetic as expected. The low molar conductance values indicate that Ni(II) and Zn(II) complexes are non electrolytes; Fe(II), Co(II), Cu(II) and UO2(II) complexes are 1:2 electrolytes while Fe(III) complex is a 1:3 electrolyte. The general compositions of the complexes are found to be [M(HL)X2]·nH2O where M=Ni(II) (X=Cl, n=1) and Zn(II) (X=Br, n=0); and [M(HL)2]Xm·nH2O where M=Fe(II) (X=Cl, m=2, n=0), Fe(III) (X=Cl, m=3, n=4), Co(II) (X=Cl, m=2, n=0), Cu(II) (X=Cl, m=2, n=0) and UO2(II) (X=NO3, m=2, n=0). The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method.
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El-Gamel, N., Mohamed, G. Synthesis, spectral and thermal characterization of 6-hydroxymethyl pyridine-2-carboxylic acid methyl ester and its complexes. J Therm Anal Calorim 81, 111–118 (2005). https://doi.org/10.1007/s10973-005-0753-z
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DOI: https://doi.org/10.1007/s10973-005-0753-z