Association constant of β-cyclodextrin with carboranes, adamantane, and their derivatives using displacement binding technique

Abstract

The association constants ( $$\text{K}_{\text{a}}^{\prime }$$ ) of unsubstituted o-, m-, and p-carborane, as well as that of adamantane, with β-Cyclodextrin are reported for the first time using displacement binding in an aqueous solution. The $$\text{K}_{\text{a}}^{\prime }$$ of several derivatives of these species are reported as well. The limitations of the displacement binding technique are also explored. Although hydrophobicity plays a major role in the association with β-CD, unsubstituted o-carborane, which is the least hydrophobic of the carborane derivatives, exhibits the highest $$\text{K}_{\text{a}}^{\prime }$$ of 2690 M−1. The $$\text{K}_{\text{a}}^{\prime }$$ values for the m- and p-carborane isomers decrease with decreasing dipole moment (1830 M−1 and 1560 M−1 respectively). Unsubstituted adamantane exhibits a $$\text{K}_{\text{a}}^{\prime }$$ value lower than each of the three carborane isomers at 1410 M−1.