Molecular Crystals and Liquid Crystals, Vol.440, 23-35, 2005
Characterization of the crystalline nature of the racemates of novel chiral five-membered cyclic nitroxides
Racemic samples of chiral five-membered cyclic nitroxides, 2,2,5,5-tetrasubstituted pyrrolidine-1-oxyls bearing one or two 4-hydroxyphenyl groups on the stereogenic centers [C(2) or C(2) & C(5)] adjacent to the NO radical moiety, exist as a racemic conglomerate in the crystalline state, whereas those having one or two 3-hydroxyphenyl groups at the same positions belong to a racemic compound. The key intermolecular interactions in controlling whether these racemates crystallize in a homochiral way or a heterochiral manner have been investigated by X-ray crystallographic analysis and magnetic susceptibility measurements.
Keywords:chiral nitroxide radical;electron paramagnetic resonance spectroscopy;magnetic susceptibility;racemic compound;racemic conglomerate;X-ray crystallographic analysis