Abstract
The formation of an ion-associated complex between of the anionic chelate of germanium(IV) with 4-nitrocatechol (4- NC) and the cation of 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (TV) was investigated by spectrophotometry. The optimum conditions for the chelate formation and the extraction of the complex in the liquid-liquid extraction system Ge(IV)α4-NCαTVαH2OαCHCl3 were established. The validity of Beer's law was checked and some analytical characteristics were calculated. The association process in the aqueous phase and the extraction equilibria were studied and quantitatively characterized by the following key constants: association constant, distribution constant, extraction constant and recovery factor. The molar ratios of the components in the ion-associated complex were determined by independent methods. Based on this, a reaction scheme, a general formula and a structure of the ion-associated complex were suggested.
Highlights
The germanium is a forth-period post-transition metal which forms complexes with various natural organic ligands, containing O, N and S donor atoms, such as polyphenols and their functional derivatives, polyhydroxycarboxylic acids, aminopolyhydroxycarboxylic acids, thiopolycarboxylic acids, 8-hydroxyquinoline and its derivatives, aromatic derivates of hydroxyaldehydes and hydroxyketones, hydroxyazodyes.[1,2,3,4,5,6,7,8,9]
The colored anionic chelate of germanium(IV)–4-NC can be efficiently extracted in chloroform in the presence of the bulky hydrophobic organic cations of monotetrazolium salt (TV)
The performed experiments showed that the complex formation and the extraction of the ion-associated complex have occurred in the dilute solutions and the molar ratio established by the independent methods mentioned above was Ge(IV):4NC:TV = 1:3:2
Summary
The germanium is a forth-period post-transition metal which forms complexes with various natural organic ligands, containing O, N and S donor atoms, such as polyphenols and their functional derivatives, polyhydroxycarboxylic acids, aminopolyhydroxycarboxylic acids, thiopolycarboxylic acids, 8-hydroxyquinoline and its derivatives, aromatic derivates of hydroxyaldehydes and hydroxyketones, hydroxyazodyes.[1,2,3,4,5,6,7,8,9] The colored anionic chelates of Ge(IV) form ion-associated complexes with bulky organic cations, like tetradecyl(trihexyl)phosphonium, methyltrioctylammonium, cetylpyridinium, cetyltrimethylammonium, tetraphenylammonium, tetraphenylarsonium.[10,11,12,13,14,15,16]The structure and the properties of the tetrazolium salts determine their ability to form ion-associated complexes.[17,18] The bulky hydrophobic organic substituents in the molecules of the tetrazolium salts increase the extractability of the ion-associated complexes. Tion in the aqueous phase (CGe(IV), μg mL‒1) and the absorbance of the ion-association complex in the organic phase after extraction was studied using regression analysis under the optimum conditions for complex formation.
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