title: Cooperative interaction of hydronium ion with an ethereally fenced hexaarylbenzene-based receptor: an NMR and theoretical study.
abstract: Using (1)H and (13)C NMR and DFT calculations, the structure and interactions of the symmetric ethereally fenced hexaarylbenzene receptor 1 with hydronium ions were studied. Both 1 and its equimolecular complex 1.H(3)O(+) exhibit C(3v) symmetry. According to DFT, two similar optimal structures of the complex exist, the more stable one being 15.4 kJ/mol lower in energy. The equilibrium between 1 and 1.H(3)O(+) complexes is characterized by the stabilization constant K = 1.97 x 10(6) (i.e., the binding constant eta = 6.3) according to both proton and carbon NMR spectra. The exchange dynamics between 1 and the complex measured by the delay-varied CPMG sequence had to be corrected for the internal exchange processes in both 1 (conformation change) and the complex (vacillation between the two minima). After this correction, the correlation time of exchange was found to be 4.76 x 10(-5) s. Such relatively fast exchange can be explained only by it being mediated by the excess water molecules present in the system.
authors.affiliation: Institute of Macromolecular Chemistry AS CR, v. v. i., Heyrovského Sq. 2, 162 06 Prague, Czech Republic. kriz@imc.cas.cz
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Kríz
authors.forename: Petr
authors.initials: P
authors.lastname: Toman
authors.forename: Emanuel
authors.initials: E
authors.lastname: Makrlík
authors.forename: Jan
authors.initials: J
authors.lastname: Budka
authors.forename: Ruchi
authors.initials: R
authors.lastname: Shukla
authors.forename: Rajendra
authors.initials: R
authors.lastname: Rathore
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009861:Onium Compounds / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D009861:Onium Compounds; C027727:hydronium ion