Crystal Structure Studies and Bronchodilation Properties of Novel Benzocycloheptapyridines

Benzocycloheptapyridines 6a and 6b were characterized by single crystal X-ray diffraction. Molecular packing exhibits that, molecules of compound 6a are linked in chains by one hydrogen bond of C–H···N type and set of H–π, and Cl–π interactions. However, compound 6b is stabilized by only Cl–π interactions. The main conformational difference between the experimental and theoretical optimized structures (using AM1, PM3 and DFT) was found in the relative orientation of the dichlorophenyl ring attached to the benzocycloheptapyridine system, which is attributed to the effect of the bulky chloride atom that prevents free rotation around the sigma bond attaching this ring with the heterocyclic system. Also, the lattice form plays an important role affecting the observed conformation. A similar behavior is also exhibited for the methyl group of the ethoxy function of 6b . The synthesized 6a reveals bronchodilation potency greater than that of the standard reference used, theophylline. Graphical Abstract Benzocycloheptapyridines were characterized by single crystal X-ray diffraction. Computational chemistry studies (AM1, PM3 and DFT) support the molecular structures. The synthesized analogues reveal promising bronchodilation properties.