An electron spin density matrix description of nuclear spin–lattice relaxation in paramagnetic molecules

Publisher Website
Google Scholar
Abstract
A density matrix treatment applicable to molecular electronic systems is formulated and used to derive an expression for the spin–lattice relaxation rate (T−11) of ligand nuclei in paramagnetic transition‐metal complexes. In this way the unpaired spin density is introduced into the nuclear relaxation expression. The two‐center dipolar integrals which occur in the expression for T1 are evaluated by a method based on solid spherical harmonic expansions whereby the Hamiltonian operator is reexpressed in terms of coordinates with respect to the orbital’s origin. The theory is used to treat 13C and 1H spin–lattice relaxation in ruthenium acetylacetonate. Good agreement is found between the calculated and experimental ratio TC1/TH1 whereas the Solomon–Bloembergen point‐dipole approach yields results significantly in variance with the experimental. The theory is used to treat proton spin relaxation in a representative low‐spin Fe(III) complex to demonstrate under what conditions the point‐dipole approximation is invalidated.

This publication has 31 references indexed in Scilit: