Theoretical spin density in nitroxides

Abstract

The influence of alkyl substitution on the spin density distribution in nitroxide radicals is studied by performing ab initio UHF calculations on a series of radicals from H2NO to C5H10NO. Comparison of spin populations and spin density maps in the series shows a net spin migration from oxygen to nitrogen when hydrogens are replaced by methyl groups. This result does not depend on the size of the alkyl substituents. The substitution effect explains in part the discrepancy between the theoretical spin density in H2NO and the experimental result obtained by polarized neutron diffraction on tanol suberate biradical C8H12O4((CH3)4C5H5NO)2.