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

Synthesis, FTIR, ¹³C-NMR and temperature-dependent ¹H-NMR characteristics of bis-naphthalimide derivatives

Chemotherapy is still the most important method of cancer treatment. To make this method more effective and safe, new drugs to destroy cancer cells are needed. Some bis-naphthalimide derivatives show potential anticancer activity via an intercalation mechanism. A higher degree of DNA intercalation corresponds to better therapeutic effects. The degree of intercalation of naphthalimides depends on their structure, molecular dynamics and intermolecular interactions with DNA. In order to apply any active substance as a drug, its molecular dynamics as well as possible interactions with target molecules have to be examined in exhaustive details. This paper describes a practical preparation of some novel bis-naphthalimide derivatives with different functional groups and their FTIR and ¹H- and ¹³C-NMR spectral characteristics. To determine the molecular dynamics of the obtained compounds the temperature, their ¹H-NMR spectra were measured. It has been clearly proven in this paper that the unusual temperature-dependent ¹H-NMR behavior of the aromatic protons of phthalimide derivatives, previously described in the literature as "hypersensitivity" and explained by n-π interactions and molecular motions of aromatic amide rings, is a result of temperature driven changes of the geometry of carbonyl groups.