Thermodynamic and Structural Studies of Metal Complexes in Solution and its Application to Analytical Chemistry

在N，N-二甲基甲酰胺(DMF)和乙腈(MeCN)中，用量热法和分光光度法研究了吡啶(Py)、3-甲基吡啶(3Me-py)和4-甲基吡啶(4Me-py)与二价过渡金属离子的络合作用。结果表明，[ML4]^&lt；2+&gt；配合物(M=Co，Ni，Cu)的结构为八面体，而[ZnL4]^&lt；2+&gt；配合物的结构为四面体。这与我们的EXAFS(扩展X射线吸收精细结构)测量结果一致，表明在4Me-py和3Me-py中，锰(II)、钴(II)和镍(II)离子的溶剂化结构是六配位的八面体，而在4Me-py中，锌(II)离子的溶剂化结构是四坐标四面体。用滴定量热法研究了18-冠-6与碱金属、碱土金属和氨离子在不同非质子溶剂和水中的络合反应。18-冠-6在非质子溶剂中的络合比在水中的络合更有利。然而，…的反应热焓和反应熵更多的r，在不同的溶剂中差别很大。因此，18-冠-6的络合反应反映了18-冠-6溶剂化程度的不同，也反映了溶剂结构的不同程度。用量热法研究了DMF-MeCN体系中18-冠-6与碱土金属离子的络合反应，结果表明，在DMF-MeCN体系中，金属离子优先与DMF分子溶剂化，18-冠-6与MeCN分子优先溶剂化。在过氧化氢存在下，3-甲基-2-苯并噻唑酮肼与N-乙基-N-(2-羟基-3-磺丙基)-3，5-二甲氧基苯胺发生氧化偶联反应，建立了测定超痕量铜(II)的新方法。在该反应中，吡啶是催化铜(II)的有效活化剂。建立了一次进样同时测定钒(V)-钒(IV)、铁(III)-钒(V)和铁(III)-铬(VI)的流动注射分析方法。在1，10-邻菲咯啉(Phen)存在下，铁(III)很容易被钒(IV)还原为铁(II)，随后生成红铁(II)-phen络合物(λ_lt；max&gt；=510 nm)，该峰与铁(III)的浓度对应。另一方面，在二磷酸存在下，钒(V)和/或铬(VI)与铁(II)的还原很容易发生，并在510 nm处产生与钒(V)和/或铬(VI)浓度对应的负FIA峰。较少

Complexation of pyridine (py), 3-methylpyridine (3Me-py) and 4-methylpyridine (4Me-py) with bivalent transition metal ions has been investigated by calorimetry and spectrophotometry in N,N-dimethylformamide (DMF) and acetonitrile (MeCN). It was revealed that the structure of the [ML_4] ^<2+> complexes (M=Co, Ni, Cu) is octahedral, while that of the [ZnL_4] ^<2+> complex is tetrahedral. This is consistent with our EXAFS (extended X-ray absorption fine structure) measurements showing that the solvation structure of the manganese (II), coblt (II) and nickel (II) ions is six-coordinate octahedral in 4Me-py and 3Me-py, while that of the zinc (II) ion is four-coordinate tetrahedral in 4Me-py. Complexation of 18-crown-6 with alkali-metal, alkaline earth metal and ammonium ions in various aprotic solvents and water has been investigated by titration calorimetry. The complexation of 18-crown-6 is more favorable in the aprotic solvents than in water. The reaction enthalpies and entropies, howeve … More r, differ much among the solvents. Thus the complexation of 18-crown-6 reflects the different solvation of 18-crown-6 and also the different degree of solvent strucutre. Complexation of 18-crown-6 with alkaline earth metal ions in DMF-MeCN mixtures has also been investigated by calorimetry and it was indicated that the metal ions are preferentially solvated with DMF molecules and 18-crown-6 is preferentially solvated with MeCN molecules in DMF-MeCN mixtures.A spectrophotometric method was developed for the determination of ultratrace amounts of copper (II) based on its catalytic effect on the oxidative coupling reaction of 3-methyl-2-benzothiazolinone hydrazone with N-ethyl-N- (2-hydroxy-3-sulfopropyl) -3,5-dimethoxyaniline to produce an intensely colored dye in the presence of hydrogen peroxide. In this reaction, pyridine acted as an effective activator for the catalysis of copper (II). A flow injection analysis (FIA) method was developed for the simultaneous determinations of vanadium (V) -vanadium (IV), of iron (III)-vanadium (V) and of iron (III) -chromium (VI) using a single injection. In the presence of 1,10-phenanthroline (phen), iron (III) is easily reduced by vanadium (IV) to iron (II), followed by the formation of a red iron (II) -phen complex (lambda_<max>=510 nm), which shows a positive FIA peak corresponding to the concentration of iron (III). On the other hand, in the presence of diphosphate reductions of vanadium (V) and/or chromium (VI) with iron (II) occur easily and a negative FIA peak at 510nm corresponding to the concentration of vanadium (V) and/or chromium (VI) is obtained. Less