Characterization and structural study of the complex of Al(III) with 2,4-dihydroxy-benzophenone. Ionic strength and solvent effects
| Autor: | S.L. Arce, F.H. Ferretti, G.T. Castro, S.E. Blanco |
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| Rok vydání: | 2003 |
| Předmět: |
Chemistry
Ligand Osmolar Concentration Molar absorptivity Atomic and Molecular Physics and Optics Chemistry Techniques Analytical Analytical Chemistry Ion Benzophenones Ionic strength Computational chemistry Covalent bond Stability constants of complexes Solvents Physical chemistry Chemical stability Spectrophotometry Ultraviolet Solvent effects Instrumentation Spectroscopy Aluminum |
| Zdroj: | Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 59(12) |
| ISSN: | 1386-1425 |
| Popis: | The complexation reaction between AlCl3 and 2,4-dihydroxy-benzophenone with varying permittivity and ionic strength of the reaction medium was investigated by theoretical and experimental procedures, namely, density functional (DFT) and UV–vis spectroscopic methods, respectively. The stoichiometric composition of the complex formed, which was determined by means of the molar ratio method, is 1:1. The molar absorptivity and stability constant of the complex were determined using a method designed by the authors. It was observed that the stoichiometric composition of the complex does not change with the used solvents and that the stability constant in methanol is higher than ethanol. Kinetic experiments in solutions with different ionic strength were also performed. The results obtained permit to conclude that the complex is formed through of a mechanism whose rate-determining step is a reaction between two ions with opposite unitary charges. In the theoretical study performed at the B3LYP/6-31G(d) level of theory using Tomasi's model, it was proposed that the formation of the complex involves one simple covalent bond between the aluminum atom and the oxygen atom of o-hydroxyl group of the ligand and a stronger coulombic attraction (or a second covalent bond) between the central atom and the carbonyl oxygen atom of 2,4-dihydroxy-benzophenone. Using the calculated magnitudes, it was predicted that the complex formed has higher thermodynamic stability in methanol than ethanol. It was also concluded that the planarity of the chelate ring favors a greater planarity of 4-hydroxy-benzoyl group of the complex with respect to the ligand, which agrees with the observed batochromic shifts. The formulated theoretical conclusions satisfactorily match the experimental determinations performed. |
| Databáze: | OpenAIRE |
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