Department of Chemistry, University of California, Berkeley, and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, USA.
J Am Chem Soc. 2010 Feb 3;132(4):1182-3. doi: 10.1021/ja905170x.
The self-assembled supramolecular host Ga(4)L(6) can bind cationic guest molecules to both the interior and exterior of the host assembly through noncovalent interactions. Very small equilibrium isotope effects (EIEs) have been precisely measured for the association of benzyltrimethylphosphonium isotopologues to the host exterior surface by adapting an NMR titration method originally developed by the Perrin group for measuring isotope effects on acidity constants. Deuteration of the phosphonium methyl groups was found to have a larger EIE than deuteration at the ring and benzyl positions, suggesting subtle differences in the noncovalent interactions between the host exterior and different guest C-H/D bonds. The application of this method to the measurement of EIEs on noncovalent host-guest interactions demonstrates the generality of this NMR technique in precisely measuring relative equilibrium constants.
自组装超分子主体Ga(4)L(6)可以通过非共价相互作用将阳离子客体分子结合到主体组装体的内部和外部。通过改编最初由 Perrin 小组开发的用于测量酸度常数上同位素效应的 NMR 滴定法，精确测量了苯甲基三甲基膦同位素标记物与主体外表面缔合的非常小的平衡同位素效应 (EIE)。发现磷鎓甲基的氘化比环和苄基位置的氘化具有更大的 EIE，这表明主体外部与不同客体 C-H/D 键之间的非共价相互作用存在细微差异。该方法在非共价主体-客体相互作用的 EIE 测量中的应用证明了该 NMR 技术在精确测量相对平衡常数方面的通用性。
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