Inclusion complex of 2-chlorobenzophenone with cyclomaltoheptaose (β-cyclodextrin): Temperature, solvent effects and molecular modeling
A thermodynamic study of the inclusion process between 2-chlorobenzophenone (2ClBP) and cyclomaltoheptaose (β-cyclodextrin, β-CD) was performed using UV-vis spectroscopy, reversed-phase liquid chromatography (RP-HPLC), and molecular modeling (PM6). Spectrophotometric measurements in aqueous solution...
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2011
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00086215_v346_n13_p1978_Sancho http://hdl.handle.net/20.500.12110/paper_00086215_v346_n13_p1978_Sancho |
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| Sumario: | A thermodynamic study of the inclusion process between 2-chlorobenzophenone (2ClBP) and cyclomaltoheptaose (β-cyclodextrin, β-CD) was performed using UV-vis spectroscopy, reversed-phase liquid chromatography (RP-HPLC), and molecular modeling (PM6). Spectrophotometric measurements in aqueous solutions were performed at different temperatures. The stoichiometry of the complex is 1:1 and its apparent formation constant (Kc) is 3846 M-1 at 30 °C. Temperature dependence of Kc values revealed that both enthalpy (δH° = -10.58 kJ/mol) and entropy changes (δS° = 33.76 J/K mol) are favorable for the inclusion process in an aqueous medium. Encapsulation was also investigated using RP-HPLC (C18 column) with different mobile-phase compositions, to which β-CD was added. The apparent formation constants in MeOH-H2O (KF) were dependent of the proportion of the mobile phase employed (50:50, 55:45, 60:40 and 65:35, v/v). The KF values were 419 M-1 (50% MeOH) and 166 M -1 (65% MeOH) at 30 °C. The thermodynamic parameters of the complex in an aqueous MeOH medium indicated that this process is largely driven by enthalpy change (δH° = -27.25 kJ/mol and δS° = -45.12 J/K mol). The results of the study carried out with the PM6 semiempirical method showed that the energetically most favorable structure for the formation of the complex is the 'head up' orientation. © 2011 Elsevier Ltd. All rights reserved. |
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