Theoretical study of the interaction between carbon-carbon triple bonds in cyclic diynes: a combined DFT and QTAIM approach

The aim of the present study is to investigate the nature of the intramolecular interaction that operates between the carbon-carbon triple bonds of cyclic diynes. A topological analysis of the electronic charge density of eight cyclic diynes, each one with a different molecular bridge, unravels the presence of a bond critical point, BCP(3,-1), along the bond path linking pairs of carbon-carbon triple bonds. Both the Laplacian of the charge density and the total energy density of the title BCP(3,-1) indicate that closed shell, intramolecular interactions are operative in these molecules. Furthermore, a complementary analysis of the frontier molecular orbitals of the cyclic diynes also reveals the presence of favorable bonding interactions.