Crystal and Molecular Structures of Methylcytisine Nitro-Derivatives

Crystal structures of the two isomers N-methyl-11-nitro- and N-methyl-9-nitrocytisine (I and II) were investigated in detail using a combination of x-ray crystal structure analysis and quantum-chemical calculations. The unit cells of both isomers contained two symmetrically independent molecules. This fact was explained and reasons for the very substantial differences in the densities and melting points of crystals of the isomers were discussed.