Carbon-13 contact shifts and spin delocalization mechanism for substituted anilines complexed with gadolinium(III) chelates

Abstract

The Gd (fod)₃- induced ¹³C shifts for a series of aniline derivatives in CDCl₃ were measured. These shifts were well interpreted by the superposition of the spin density distributions of the carbon 2s-orbitals of the aniline cation radical and the corresponding phenyl radical. This may imply two kinds of contact shift contributions due to a through-bond delocalization of β-spin and a through-space transfer of α-spin from Gd³⁺ to aniline. Furthermore, the tentative addition of a third contribution to the observed shifts, relative pseudo-contact shifts, led to a better fit to the experimental shift patterns, and thus, this result suggests the possibility that Gd³⁺complexes are magnetically anisotropic.