Water Structure Recovery in Chaotropic Anion Recognition: High‐Affinity Binding of Dodecaborate Clusters to γ‐Cyclodextrin |
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| Authors: | Khaleel I Assaf Merve S Ural Dr Fangfang Pan Tony Georgiev Prof Svetlana Simova Prof Kari Rissanen Prof Detlef Gabel Prof Werner M Nau |
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| Institution: | 1. Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany);2. University of Jyvaskyla, Department of Chemistry, Nanoscience Center, P.O. Box. 35, 40014 University of Jyvaskyla (Finland);3. Institute of Organic Chemistry with Center of Phytochemistry, Bulgarian Academy of Science, 1113 Sofia (Bulgaria) |
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| Abstract: | Dodecaborate anions of the type B12X122? and B12X11Y2? (X=H, Cl, Br, I and Y=OH, SH, NH3+, NR3+) form strong (Ka up to 106 L mol?1, for B12Br122?) inclusion complexes with γ‐cyclodextrin (γ‐CD). The micromolar affinities reached are the highest known for this native CD. The complexation exhibits highly negative enthalpies (up to ?25 kcal mol?1) and entropies (TΔS up to ?18.4 kcal mol?1, both for B12I122?), which position these guests at the bottom end of the well‐known enthalpy‐entropy correlation for CDs. The high driving force can be traced back to a chaotropic effect, according to which chaotropic anions have an intrinsic affinity to hydrophobic cavities in aqueous solution. In line with this argument, salting‐in effects revealed dodecaborates as superchaotropic dianions. |
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| Keywords: | boron clusters cyclodextrins Hofmeister series host– guest complexes supramolecular chemistry |
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