Synthesis of Deuterium-Labeled Cryptophane-A and Investigation of Xe@Cryptophane Complexation Dynamics by 1D-EXSY NMR Experiments
✍ Scribed by Thierry Brotin; Thomas Devic; Anne Lesage; Lyndon Emsley; André Collet
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 225 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
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 129 Xe magnetization transfer (1D-EX-SY) allows the measurement of exchange rates. From these data the de-complexation activation energy E a has been estimated to be 37.5 AE 2 kJ mol À1 . The decomplexation activation enthal-py, DH = 35.5 AE 2 kJ mol À1 , and entropy, DS = À 60 AE 5 J mol À1 K À1 , 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.