title: Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-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 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 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.
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany).
authors.forename: Khaleel I
authors.initials: KI
authors.lastname: Assaf
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany).
authors.forename: Merve S
authors.initials: MS
authors.lastname: Ural
authors.affiliation: University of Jyvaskyla, Department of Chemistry, Nanoscience Center, P.O. Box. 35, 40014 University of Jyvaskyla (Finland).
authors.forename: Fangfang
authors.initials: F
authors.lastname: Pan
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany).
authors.forename: Tony
authors.initials: T
authors.lastname: Georgiev
authors.affiliation: Institute of Organic Chemistry with Center of Phytochemistry, Bulgarian Academy of Science, 1113 Sofia (Bulgaria).
authors.forename: Svetlana
authors.initials: S
authors.lastname: Simova
authors.affiliation: University of Jyvaskyla, Department of Chemistry, Nanoscience Center, P.O. Box. 35, 40014 University of Jyvaskyla (Finland). kari.t.rissanen@jyu.fi.
authors.forename: Kari
authors.initials: K
authors.lastname: Rissanen
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany). d.gabel@jacobs-university.de.
authors.forename: Detlef
authors.initials: D
authors.lastname: Gabel
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany). w.nau@jacobs-university.de.
authors.forename: Werner M
authors.initials: WM
authors.lastname: Nau
mesh_terms: D000838:Anions / Q000737:chemistry; D001665:Binding Sites; D001896:Boron Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*; D047408:gamma-Cyclodextrins / Q000737:chemistry*
chemical_list: D000838:Anions; D001896:Boron Compounds; D047408:gamma-Cyclodextrins; D014867:Water; C119788:dodecaborate; C023792:gamma-cyclodextrin
keywords: Hofmeister series; boron clusters; cyclodextrins; host-guest complexes; supramolecular chemistry