Solvation of alkylaromatic hydrocarbons towards a paramagnetic relaxation reagent, tris(acetylacetonato)chromium(III)

Abstract

AbstractA 13C electron–nuclear spin–lattice relaxation study showed that the interaction between alkyl‐substituted aromatics and a paramagnetic relaxation reagent, tris(acetylacetonato)chromium(III), is purely electrostatic, i.e. of a dipole–dipole or dipole–induced dipole type. Except for aromatics having bulky alkyl groups, the preferred chelate position is close to the positive end of the dipole, i.e. close to the α‐position. However, the major electron–nuclear mechanism is non‐specific, and the relaxation rate is mainly controlled by the mutual translational/rotational diffusion of the two species. Paramagnetic shifts induced on addition of Cr(acac)3 support the suggested interaction mechanism.