Study in Aqueous Solutions of Bioactive 2-Pyridineformamide-Derived Thiosemicarbazones and Their Iron(II) and Iron(III) Complexes

作者：Vilhena Felipe S^*; Teixeira Leticia R; Alves Odivaldo Cambraia; Beraldo Heloisa; Miranda Fabio da S; Felcman Judith

来源：Journal of Solution Chemistry, 2013, 42(3): 555-565.

DOI：10.1007/s10953-013-9977-x

• 2-Pyridineformamide thiosemicarbazones
• Iron complexes
• Stability constants
• EPR spectroscopy

The binary systems of iron(II) and iron(III) with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives were studied in aqueous solution by pH-potentiometry, ultraviolet-visible spectroscopy and EPR spectra. The formation constants of the iron(II) and iron(III) complexes were calculated from potentiometric and electronic absorption data at 25 A degrees C and ionic strength mu = 0.1 mol center dot L-1 using the HYPERQUAD program. The values of the formation constant of the FeL species decrease in the order Fe:H2Am4DH %26gt; Fe:H2Am4Me a parts per thousand Fe:H2Am4Et %26gt; Fe:H2Am4Ph in the same way as the basicity of the ligands. The species distribution diagrams show that the species FeL2 predominates at physiological pH in the Fe:H2Am4DH, Fe:H2Am4Me and Fe:H2Am4Et systems. The similar EPR spectra of these iron(III) binary systems indicate the same coordination spheres around the metallic center and the EPR g values suggests that the unpaired electron is in the d(xy) orbital, indicating a d (xz) (2) d (yz) (2) d (xy) (1) ground state configuration for the complexes. For the Fe(III):H2Am4Ph system the EPR results indicated dimerization and antiferromagnetic interaction due to the presence of only one thiosemicarbazone ligand around the metallic center.

• 出版日期2013-3