sigma/pi versus pi/pi Conjugation: DFT Studies on Oligocyclopropenones and Related Systems

Abstract

DFT studies on oligocyclopropenones and related systems 5(n)-9(n) are reported. A strong sigma/pi interaction between the pi system and the or framework of the three-membered rings is observed in almost all cases, leading to a perpendicular arrangement of the pi systems in the most favored conformation. Also the shape of cyclic congeners is strongly influenced by sigma/pi interactions.