ヘテロ環状ヒドラゾン系有機試薬の分析化学的応用に関する研究
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概要
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Although a large number of nitrogen-heterocyclic hydrazones have been used as chromogenic reagents in the spectrophotometric determination of divalent transition metal ions, there is only a little information on the complexation behavior of these hydrazones in terms of thermodynamics and kinetics. In order to increase sensitivity or solubility, bulky substituents such as pyridyl and quinolyl groups are often introduced into extractive-spectrophotometric reagents. However application of linear free energy relationship (LFER) to formation of metal-multidentate ligand complexes has been scarcely discussed. In this study, the extractive-spectrophotometric determination of trace metal ions and anions with hydrazones were established. The extraction behavior was interpreted in terms of complexation parameters in aqueous or aqueous-dioxane solution and LFER. The extraction mechanisms were confirmed by equilibrium and kinetic experiments. First, the acid-base equilibria were discussed in connection with the ligand structures with the aid of several spectrometric (NMR, X-ray etc.) results. Second, the formation constants of the Ni(II). Cu(II) and Fe(II) complexes with a series of hydrazones were determined. The LFER between formation and proton dissociation constants showed several structural effects, in addition to the effect of basicity, which were caused by the N, N, N-heterocyclic structure. The LFER obtained were discussed in connection with thermodynamic and ligand field parameters and were reasonably explained by the additivity of the structural effects on the formation constants. Thirdly, the extraction equilibria of nickel(II) were elucidated based on the results of the second study. The extraction kinetics was discussed in conjunction with the rate constants of formation of nickel(II)-hydrazone complexes. Finally, a method for the determination of trace elements with hydrazones having a di-2-pyridyl ketone moiety was proposed and some favourable effects of the ketone moiety were discussed.
- 社団法人日本分析化学会の論文
- 1996-01-05