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Isolation of Selected Exchange Processes in Nuclear Magnetic Resonance
Author(s) -
Zwahlen Catherine,
Vincent Sébastien J. F.,
Schwager Martina,
Bodenhausen Geoffrey
Publication year - 1996
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/chem.19960020110
Subject(s) - magnetization , magnetization transfer , chemistry , inversion (geology) , ligand (biochemistry) , nuclear magnetic resonance , physics , magnetic resonance imaging , magnetic field , biology , medicine , paleontology , biochemistry , receptor , quantum mechanics , structural basin , radiology
We have shown that it is possible to inhibit the transfer of magnetization in a system with several exchanging sites in dynamic equilibrium, as in a mixture of cis ‐ and trans ‐ZrCl 4 L 2 with excess free ligand L (L = (CH 3 O) 3 PO). The forward and backward reaction rates involving two selected sites can be studied while the effect of competing exchange processes is “quenched”. This can be achieved either by selective inversion of the magnetization of the two chosen sites in the course of the reaction interval, or alternatively by inversion of the magnetization of all other sites in the exchange network. The rate of exchange from the free to the cis site was determined to be k cis←free = 0.018 s −1 . In the usual methods, this process would tend to be overshadowed by the almost two hundred times faster competing exchange process from the cis to the trans site ( K trans←cis = 3.32 s −1 ).