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Deuterium isotope effects on 13C chemical shifts of negatively charged NH…N systems

Authors


Correspondence to: Mariusz Pietrzak, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland. E-mail: mpietrzak@ichf.edu.pl

Correspondence to: Poul Erik Hansen, Department of Science, Systems and Models, Roskilde University, P.O. Box 260, DK-4000 Roskilde, Denmark. E-mail: poulerik@ruc.dk

ABSTRACT

Deuterium isotope effects on 13C chemical shifts are investigated in anions of 1,8-bis(4-toluenesulphonamido)naphthalenes together with N,N-(naphthalene-1,8-diyl)bis(2,2,2-trifluoracetamide) all with bis(1,8-dimethylamino)napthaleneH+ as counter ion. These compounds represent both “static” and equilibrium cases. NMR assignments of the former have been revised. The NH proton is deuteriated. The isotope effects on 13C chemical shifts are rather unusual in these strongly hydrogen bonded systems between a NH and a negatively charged nitrogen atom. The formal four-bond effects are found to be negative indicating transmission via the hydrogen bond. In addition, unusual long range effects are seen. Structures, 1H and 13C NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using density functional theory methods. Copyright © 2013 John Wiley & Sons, Ltd.

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