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Entropy‐Driven Cooperativity in the Guest Binding of an Octaphosphonate Bis‐cavitand
Author(s) -
Shimoyama Daisuke,
Haino Takeharu
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201905036
Subject(s) - isothermal titration calorimetry , cavitand , chemistry , chloroform , hydrogen bond , cooperativity , enthalpy , titration , cooperative binding , entropy (arrow of time) , calorimetry , molecule , thermodynamics , supramolecular chemistry , crystallography , organic chemistry , biochemistry , physics , enzyme
Abstract Uncommon entropy‐driven cooperativity is reported in the guest binding of an octaphosphonate bis‐cavitand. Isothermal titration calorimetry determined the thermodynamic parameters for the 1:2 host–guest binding of bis‐cavitands with ammonium guests in methanol, ethanol, 2‐propanol, and chloroform. Chloroform drove uncommon entropy‐driven cooperative binding, whereas the alcohols resulted in enthalpy‐driven noncooperative binding. 1 H NMR studies revealed that each cavity contained six water molecules in chloroform, which were liberated on guest binding. The enthalpy–entropy compensation relationship produced a large positive intrinsic entropy in chloroform, which implies that water desolvation causes a considerable entropic gain by paying an enthalpic penalty due to breaking the hydrogen‐bonding networks of the water clusters.