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

Deuterium isotope effects on C-13 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 C-13 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, H-1 and C-13 NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using density functional theory methods. Copyright (c) 2013 John Wiley & Sons, Ltd.