Binding Energies and 19F Nuclear Magnetic Deshielding in Paramagnetic Halogen-Bonded Complexes of TEMPO with Haloperfluorocarbons |
J. Phys. Chem. A 2008, 112 (40), 9911-9918 |
C. Cavallotti, P. Metrangolo, F. Meyer, F. Recupero, G. Resnati |
![]() |
Formation of the TEMPO-Halo-PFC Complex |
19F NMR measurements and theoretical calculations were performed to study paramagnetic complexes of
iodoperfluorocarbons with stable nitroxide radicals. Contrary to what is usually measured for diamagnetic
halogen-bonded complexes involving iodoperfluorocarbons, it was found that the formation of complexes
with the 2,2,6,6-tetramethyl(piperidin-1-yloxyl) (TEMPO) radical determines downfield shifts in the 19F NMR
spectra. The experimental finding was confirmed by calculating nuclear shielding using density functional
theory and correcting the isotropic diamagnetic 19F chemical shift with contact interactions evaluated from
the hyperfine coupling tensor. The computational analysis of the interaction between CF3I and TEMPO, by
using DFT and MP2 theories, showed that the occurrence of the halogen bond between the interacting partners
is associated with a significant charge transfer to CF3I and that the measured downfield shift is due to the
occurring spin transfer.
|