Supramolecular Host鈥揋uest Interactions of Oxazine-1 Dye with 尾- and 纬-Cyclodextrins: A Photophysical and Quantum Chemical Study

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• 作者：Mhejabeen Shaikh ; Jyotirmayee Mohanty ; Mahesh Sundararajan ; Achikanath C. Bhasikuttan ; Haridas Pal
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：October 18, 2012
• 年：2012
• 卷：116
• 期：41
• 页码：12450-12459
• 全文大小：567K
• 年卷期：v.116,no.41(October 18, 2012)
• ISSN：1520-5207

文摘

Supramolecular host鈥揼uest interactions of oxazine-1 dye with 尾- and 纬-cyclodextrins (尾CD and 纬CD, respectively) have been investigated in neutral aqueous solution (pH 7) at ambient temperature (25 掳C) following absorption, fluorescence, and circular dichroism measurements. The dye forms inclusion complexes with both CDs, causing significant changes in its photophysical properties. Whereas fluorescence titration data for lower dye concentrations fit well with 1:1 stoichiometric complexes, the time-resolved fluorescence results indicate formation of a small extent of 1:2 (dye鈥揾ost) complexes as well, especially at higher CD concentrations. The moderate range of the binding constant values for the present systems indicates the weaker hydrophobic interaction as responsible for the inclusion complex formation in these systems. It has also been observed that 纬CD facilitates dimerization of the dye, prominently indicated at the higher dye concentrations. On the contrary, 尾CD always assists deaggregation of the dye, even at very high dye concentrations. Time-resolved fluorescence anisotropy results qualitatively support the inclusion complex formation in the present systems. Results from quantum chemical calculations also nicely corroborate with the inferences drawn from photophysical studies. Observed results demonstrate that the size compatibility of the guest and the host cavity mainly determines the host鈥揼uest interaction in the present systems, much similar to the substrate鈥揷atalyst binding in many biological systems.