Influence of steric and electronic effects of substituents on the molecular structures and conformational flexibility of 1,8-naphthalenedicarboximides

A series of 1.8-naphthalenedicarboximide derivatives containing substituents of different steric and electronic nature were studied by X-ray diffraction analysis. Ab initio quantum-chemical calculations in the HF/3-21G approximation demonstrated the high conformational flexibility of the imide tetrahydro ring in the molecules of these compounds. The electronic nature of the substituents has no effect on the geometry and conformational flexibility of naphthalenedicarboximides due to weak conjugation between the imide and naphthalene fragments in the molecules. However, the steric effects of the bulky substituents noticeably affect the equilibrium geometry of the imide ring by increasing its conformational flexibility.