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Synthesis of Deuterium‐Labeled Cryptophane‐A and Investigation of Xe@Cryptophane Complexation Dynamics by 1D‐EXSY NMR Experiments
Author(s) -
Brotin Thierry,
Devic Thomas,
Lesage Anne,
Emsley Lyndon,
Collet André
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010401)7:7<1561::aid-chem1561>3.0.co;2-9
Subject(s) - chemistry , enthalpy , deuterium , activation energy , magnetization transfer , deuterium nmr , stereochemistry , nuclear magnetic resonance spectroscopy , thermodynamics , physics , atomic physics , medicine , radiology , magnetic resonance imaging
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‐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, Δ H ≠ =35.5±2 kJ mol −1 , and entropy, Δ S ≠ =−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.