MOLECULAR GEOMETRY AND ELECTRON STRUCTURE OF 8-ARYL-3,5-DI[(E)-1-ARYLIDEN]-1,2,3,5,6,7-HEXAHYDROCYCLOPENTANO[b,e]PYRIDINES

Abstract

Series were synthesized: 8-aryl-3,5-di[(E)-1-aryliden]-1,2,3,5,6,7-hexahydrocyclopentano[b,e]pyridines. Owing to the unique chemical structure of distyrylpyridines there is an opportunity to determine their preferable geometry in solutions from the simple analysis of their 1H-NMR spectra. The spectral data confirms the preferably planar conformation for the compounds with side five-membered aromatic rings. In the case of six-membered aromatic cycles the steric hindrances appears, which induces definite violation in planarity of such molecules, but only slight distortion of conjugation between their fragments. In the cases, when additional steric hindrance exists (ortho-substituents in the side rings), the planarity of styryl fragments, and especially – the conjugation of pyridine moiety with the cycle at C-8 decreases substantially. The intramolecular charge transfer from the side aromatic to the central pyridine moiety takes place at excitation of the studied distyrylpyridine molecules. In the excited S1 state many of them must become more planar as well.