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Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to ?-Cyclodextrin.

ABSTRACT: Dodecaborate anions of the type B12X12(2-) and B12X11Y(2-) (X=H, Cl, Br, I and Y=OH, SH, NH3(+), NR3(+)) form strong (K(a) up to 10(6) L?mol(-1), for B12Br12(2-)) inclusion complexes with ?-cyclodextrin (?-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 (T?S up to -18.4?kcal?mol(-1), both for B12I12(2-)), 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.

SUBMITTER: Assaf KI

PROVIDER: S-EPMC4510780 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-Cyclodextrin.

Assaf Khaleel I KI Ural Merve S MS Pan Fangfang F Georgiev Tony T Simova Svetlana S Rissanen Kari K Gabel Detlef D Nau Werner M WM

Angewandte Chemie (International ed. in English) 20150507 23

Dodecaborate anions of the type B12X12(2-) and B12X11Y(2-) (X=H, Cl, Br, I and Y=OH, SH, NH3(+), NR3(+)) form strong (K(a) up to 10(6) L mol(-1), for B12Br12(2-)) 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 B12I12(2-)), which position these guests at the bottom end of the well-known enth ...[more]

PMID: 25951349

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