Abstract
Nitrogen shielding tensors are compared for singly-bonded nitrogen, and multiply-bonded nitrogen in linear and planar groups, including the peptide link, NOx groups, and ligands in metal complexes. In isoelectronic (isostructural) locations, nitrogen tensors resemble those for carbon or phosphorus, with scaling by the respective np factors. In nitrogen-containing chromophores, however, major deshieldings are observed for axes which mix nN (lone pair) and π*orbitals. Thus in biomolecules nitrogen shielding tensors give useful information on protonation and hydrogen bonding, and the shielding tensor affords a criterion for the bending of nitrogen in ligands in metal complexes, as demonstrated for metal nitrosyls. In the dinitrogen oxides N2O, N2O2, N2O3, and N2O4, there is a substantial contribution to the nitrogen shift from the N-N bond (as shown by LORG calculations), particularly in N2O2 in which this bond is very long.
Published Version
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