Computational Investigation of Spin Traps Using Hybrid Solvation Models.

The cyclic nitrone 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), and the lesser known linear phenyl-N-tert-butylnitrone (PBN) and its phosphorylated analogues have been used as spin traps for the investigation of free radicals in biological systems. Theoretical work on these molecules suggests that there are important differences in their properties between biological systems and isolated molecules in the gas phase, most likely resulting from intra and intermolecular hydrogen bonding. Most dielectric solvation models such as the polarized continuum model and COSMO are incapable of direct determination of solvent-spin trap chemical interactions. To examine this, hybrid models incorporating COSMO for long range effects and discrete solvent molecules for short range effects, at the DFT/B3LYP/6-31G* level of theory, have been used to study the stabilization and alteration of the spin trap molecules properties in protic and aprotic polar solvents. The hybrid models have been successfully implemented to support the prominent role played by hydrogen bonding interactions in the stabilization of spin traps