Cooperative Interaction of Hydronium Ion with an Ethereally Fenced Hexaarylbenzene-Based Receptor: An NMR and Theoretical Study

作者：Kriz Jaroslav^*; Toman Petr; Makrlik Emanuel; Budka Jan; Shukla Ruchi; Rathore Rajendra

来源：Journal of Physical Chemistry A, 2010, 114(16): 5327-5334.

DOI：10.1021/jp101080h

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 center dot 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 center dot H(3)O(+) complexes is characterized by the stabilization constant K = 1.97 x 10(6) (i.e., the binding constant n = 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.

• 出版日期2010-4-29