Thermodynamics of the complexation of mono- and bis-cyclodextrin derivatives with a polarity sensitive probe: Fluorescence, Induced Circular Dichroism and molecular modelling

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• 作者：Thais Carmona^a ; Natalia Mayordomo^a ; Katia Martina^b ; Giancarlo Cravotto^b ; Francisco Mendicuti^a ; ^{francisco.mendicuti@uah.es}
• 关键词：Cyclodextrins ; Fluorescence ; Circular dichroism ; Molecular Mechanics ; Molecular Dynamics ; 2 ; 6-Methyl naphthalenecarboxylate
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2012
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：1 June, 2012
• 卷：237
• 期：Complete
• 页码：38-48
• 文件大小：1173 K

摘要

Steady-state, time-resolved fluorescence, Induced Circular Dichroism (ICD), Molecular Mechanics and Molecular Dynamics techniques have been employed in the study of the complexation of dimethyl 2,6-naphthalenedicarboxylate (DMN), a fluorescent probe, with mono- and bis尾CD derivatives whose appended group, or 尾CD spacer, contain the 1,3-diphenoxy moiety (OB), i.e., 6[4-((3-(prop-2-ynyloxy)phenoxy)methyl]-1H-1,2,3-triazol-1-yl]6-deoxy-尾CD (m尾CD) and 1,3-bis((1-(6鈥?尾CD-6鈥?yl)-1H-1,2,3-triazol-4-yl)methoxy)benzene (b尾CD). The study also considers complexation with the native 尾CD partner. The DMN emission spectrum shows two overlapping electronic bands whose ratio of intensities, R, is very sensitive to the polarity of the medium surrounding it. The stoichiometry, the formation constants of the complexes and the 螖H and 螖S parameters upon inclusion were obtained from the change in R and weighted average lifetime, 銆?em>蟿銆? with CD concentration and temperature. DMN forms 1:1 and 2:1 stoichiometry complexes with b尾CD, but does not with m尾CD. Molecular modelling was also used to emulate the complexation processes in the presence of water. The 1:1 and 2:1 DMN/b尾CD complex structures agree with the signs of enthalpy and entropy changes. Quenching, R at infinite b尾CD concentration, fluorescence depolarization measurements and ICD spectra also support the proposed structures. Inclusion is mostly dominated by van der Waals interactions.