Ion-Regulated Allosteric Binding of Fullerenes (C60 and C70) by Tetrathiafulvalene-Calix[4]pyrroles
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- 作者：Christina M. Davis ; Jong Min Lim ; Karina R. Larsen ; Dong Sub Kim ; Young Mo Sung ; Dani M. Lyons ; Vincent M. Lynch ; Kent A. Nielsen ; Jan O. Jeppesen ; Dongho Kim ; Jung Su Park ; Jonathan L. Sessler
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：July 23, 2014
- 年：2014
- 卷：136
- 期：29
- 页码：10410-10417
- 全文大小：395K
- ISSN：1520-5126
文摘
The effect of ionic species on the binding of fullerenes (C60 and C70) by tetrathiafulvalene-calix[4]pyrrole (TTF-C4P) receptors and the nature of the resulting supramolecular complexes (TTF-C4P + fullerene + halide anion + tetraalkylammonium cation) was studied in the solid state through single crystal X-ray diffraction methods and in dichloromethane solution by means of continuous variation plots and UV鈥搗is spectroscopic titrations. These analyses revealed a 1:1 stoichiometry between the anion-bound TTF-C4Ps and the complexed fullerenes. The latter guests are bound within the bowl-like cup of the C4P in a ball-and-socket binding mode. The interactions between the TTF-C4P receptors and the fullerene guests are highly influenced by both the nature of halide anions and their counter tetraalkylammonium cations. Three halides (F鈥?/sup>, Cl鈥?/sup>, and Br鈥?/sup>) were studied. All three potentiate the binding of the two test fullerenes by inducing a conformational change from the 1,3-alternate to the cone conformer of the TTF-C4Ps, thus acting as positive heterotropic allosteric effectors. For a particular halide anion, the choice of tetraalkylammonium salts serves to modulate the strength of the TTF-C4P-fullerene host鈥揼uest binding interactions and, in conjunction with variations in the halide anion, can be exploited to alter the inherent selectivity of the host for a given fullerene. Differences in binding are reflected in the excited state optical properties. Overall, the present four-component system provides an illustration of how host鈥揼uest binding events involving appropriately designed artificial receptors can be fine-tuned via the addition of simple ionic species as allosteric modulators.