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Comparison Studies on Complexation of Molybdenum(VI) with Aspartic Acid And Glutamic Acid in Different Dielectric Constants1
| Content Provider | Semantic Scholar |
|---|---|
| Author | Azizi, Zahra Moniri, Elham Zare,, Karim Panahi, Homayoun Ahmad |
| Copyright Year | 2004 |
| Abstract | Equilibria of the reaction of molybdenum(VI) with L-aspartic acid (Asp) and LGlutamic acid (Glu) have been studied by spectrophotometric measurements in mixed solvent systems at an ionic strength of 0.2 mol/dm sodium perchlorate, employed (15, 20, 25, 30± 0.1°C) at pH ranges of 3.2 to 5.5 with a high ratio of ligand to metal. The stability constants of the complexes and the resulting free energy changes are presented. The effect of solvent systems on protonation and complexation are discussed. Linear relationships are observed by plotting logK versus 1/D , where K and D show stability and dielectric constants, respectively. INTRODUCTION So far , few investigation about the complexation of a molybdate ion in mixed solvent systems has been performed. The biochemical aspect and importance of molybdenum in enzymes present in microorganisms, plants, and animals have been investigated by Kendrick et al. [1]. The equilibria of Mo(VI) in an aqueous solution are complex, and various polynuclear species are formed in acidic solution (pH < 4.5) [2–10]. The complexation of molybdenum and aspartic acid & glutamic acid play an important role in animal and plant metabolism particularly in reactions involving transformation and transfer of amino group. Due to this fact, complexation with transitional elements and consideration of the stability of the complex could be of great value [11-13]. In this research project, the complexation of molybdenum(VI) with aspartic acid and glutamic acid have been investigated using a combination of potentiometric and spectrophotometric means in mixed solvent systems of CH3OH and H2O with a high ratio of ligand to metal employing pH ranges of 3.2 to5.5 . EXPERIMENTAL Perchloric acid Sodium perchlorate, methanol, and sodium hydroxide were supplied from Merck Chemical Co., L-aspartic acid, L-glutamic acid and sodium molybdate were purchased from Aldrich Chemical Co., and Riedel–De Haenayseelze– Hannover, respectively. Dilute perchloric acid solution was standardized against KHCO3. A 50% sodium hydroxide solution free from carbonate was prepared from analytical grade material followed by filtration through a G4 Jena glass filter and stored in a polyethylene bottle. Dilute solution was prepared from double distilled water with a specific conductivity of (1.3 ± 0.1) μΩcm and standardized against HClO4. All measurements were carried out at 15, 20, 25, and 30 ± 0.1°C. The ionic strength was maintained at 0.2 mol/dm using sodium perchlorate. A Horiba D-14 pH meter was employed for pH measurements. The hydrogen ion concentration was measured using an Ingold UO3234 glass electrode and an Ingold UO3236 calomel electrode. It is essential to calibrate the system routinely for various solvent mixtures of known hydrogen ion concentration and constant ionic strength to determine the hydrogen ion concentration [14-16]. Spectrophotometric measurements were conducted using an UV-Vis Shimadzu 2101 spectrophotometer equipped with a Acermate 486 SX/25D computer and thermostatically matched 10 mm quarts cells, employing a flow type cell and masterflex pump allowing the circulation of the solution from the potentiometric cell to the spectrophotometric cell. The absorbance and pH of the solution were measured simultaneously. The dielectric constant of mixed solvent systems of methanol in water were measured by comparing the capacitance of a capacitor with and without the * Corresponding author: E-mail: zahraazizi@yahoo.com |
| Starting Page | 49 |
| Ending Page | 56 |
| Page Count | 8 |
| File Format | PDF HTM / HTML |
| Volume Number | 1 |
| Alternate Webpage(s) | http://jptc.srbiau.ac.ir/article_6563_e6329b89cb857863dc53b21740d8e49e.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
