Relationship between electron difference-density distribution, planarity of the >N–O groups and intermolecular hydrogen bond systems in crystals of stable nitroxide radicals

摘要: Abstract The electron density distribution calculated for 2,2,6,6-tetramethyl-1-piperidinyloxy ( 1 ), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy 2 ) and 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy 3 free radicals on the basis of low-temperature X-ray single crystal diffraction experiments revealed some differences in region >N–O groups. Generally, experimental bonding along axis N–O bond is relatively low asymmetric cases pyramidal geometry aminoxyl group almost symmetrical planar ). shape densities oxygen lone-pairs suggest that this atom sp hybridized but spatial orientation these maxima depends hydrogen interactions (>N–O⋯H) studied crystals. Also relation between direction strong bonds (O⋯H