Thermodynamics Research Today is a free monthly online journal that collates and summarizes the latest research about Thermodynamics, including details on enthalpy, entropy, energy transitions.

A spectrophotometric and thermodynamic study of the charge-transfer complexes of iodine with 2-aminomethyl-15-crown-5 in chloroform and 1,2-dichloroethane solutions.

Hasani M, Akbari S

Department of Chemistry, College of Science, Bu-Ali Sina University, Hamadan 65174, Iran. hasani@basu.ac.ir

Interaction of 2-aminomethyl-15-crown-5 (AM15C5) with iodine has been investigated spectrophotometrically in chloroform and 1,2-dichloroethane (1,2-DCE) solutions. The observed time dependence of the charge-transfer band and subsequent formation of I(3)(-) in solution were related to the slow transformation of the initially formed 1:1 AM15C5.I(2) outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants were evaluated from the absorbance- and conductivity-time data. The stoichiometry and formation constants of the resulting EDA complexes have also been determined. Thermodynamic parameters, Delta H degrees and Delta S degrees , of the complexes have been determined from the temperature dependence of stability constants by Van't Hoff equation. The results indicate that iodine complexes of AM15C5 in both solvents are enthalpy stabilized but entropy destabilized. The influence of solvent properties on the kinetics and stability of the resulting charge-transfer complexes are discussed.

Published 4 April 2007 in Spectrochim Acta A Mol Biomol Spectrosc, 67(1): 139-44.
Full-text of this article is available online (may require subscription).

© 2005-2008 Thermodynamics Research Today. All Rights Reserved.