title: The Delicate Balance of Preorganisation and Adaptability in Multiply Bonded Host-Guest Complexes.
abstract: Rigidity and preorganisation are believed to be required for high affinity in multiply bonded supramolecular complexes as they help reduce the entropic penalty of the binding event. This comes at the price that such rigid complexes are sensitive to small geometric mismatches. In marked contrast, nature uses more flexible building blocks. Thus, one might consider putting the rigidity/high-affinity notion to the test. Multivalent crown/ammonium complexes are ideal for this purpose as the monovalent interaction is well understood. A series of divalent complexes with different spacer lengths and rigidities has thus been analysed to correlate chelate cooperativities and spacer properties. Too long spacers reduce chelate cooperativity compared to exactly matching ones. However, in contrast to expectation, flexible guests bind with chelate cooperativities clearly exceeding those of rigid structures. Flexible spacers adapt to small geometric host-guest mismatches. Spacer-spacer interactions help overcome the entropic penalty of conformational fixation during binding and a delicate balance of preorganisation and adaptability is at play in multivalent complexes.
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Larissa K S
authors.identifier: http://orcid.org/0000-0002-4278-5235
authors.initials: LK
authors.lastname: von Krbek
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Achazi
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schoder
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Gaedke
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Biberger
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Paulus
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195, Berlin, Germany.
authors.forename: Christoph A
authors.identifier: http://orcid.org/0000-0002-8634-3578
authors.initials: CA
authors.lastname: Schalley
keywords: chelate cooperativity; density functional calculations; isothermal titration calorimetry; multivalency; preorganisation-adaptability dichotomy