Synthesis of denterium-labeled cryptophane-A and investigation of Xe@Cryptophane complexation dynamics by 1D-EXSY NMR experiments

We present the synthesis of a series of deuterated cryptophanes 2-6 by a slightly modified procedure used for cryptophane-A. We show that for [Xe@cryptophane] complexes the use of variable-temperature one-dimensional Xe-129 magnetization transfer (1D-EXSY) allows the measurement of exchange rates. From these data the decomplexation activation energy E-a has been estimated to be 37.5 +/- 2 kJ mol(-1) The decomplexation activation enthalpy, DeltaH dagger = 35.5 +/- 2 kJ mol(-1), and entropy, DeltaS dagger = - 60 +/- 5 J mol(-1) K-1, have also been calculated. The calculated negative activation entropy suggests that the activated complex associated with decomplexation is conformationally more strained than the complex in its ground state.