期刊
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
卷 95, 期 -, 页码 1-7出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.saa.2012.04.034
关键词
Al(III)-3-hydroxyflavone complex; Spectroscopy; Stability constant; Solvent effects; Linear solvation energy relationship; DFT method
类别
资金
- National University of San Luis
- CONICET (Argentine Republic) [PIP 11220100100151]
Stoichiometry and apparent stability constant (KO of the complex formed between AI(III) and 3-hydroxyflavone were determined in methanol and water-methanol mixtures (% water w/w: 3.11; 6.15; 10.4; 15.2: 19.9 and 25.3) by UV-vis spectroscopy at 25.0 degrees C and constant ionic strength (0.05 M, sodium chloride). Stoichiometry of the complex (1:2, metal:ligand) is not modified with an increase in water percentage in the analyzed interval. The value of K-C in methanol is greater than in the binary solutions. The effects of changing solvent composition on K-C data were explained by linear solvation free energy relationships using the solvatochromic parameter of Kamlet and Taft (alpha, beta and pi*). Multiple linear regression analysis indicates that the hydrogen bond donating ability (alpha) of the solvent and non-specific interactions (pi*) play an important role in the degree of occurrence of the reaction. The effect of temperature on K-C was also analyzed by assessing standard entropy and enthalpy variations of the reaction in methanol. Finally, the structure of the complex was investigated using FTIR spectroscopy and DFT calculations. The ligand exhibits small structural changes upon complexation, localized on the chelating site. The calculated vibrational frequencies of the complex were successfully compared against the experimental values. (C) 2012 Elsevier B.V. All rights reserved.
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