Preparations, crystal structures and DFT calculation of diacetylene derivatives carrying nicotinic esters

Abstract

Novel three diacetylene derivatives 1–3, which carry a pyridine ring as a pendant group, have been successfully prepared and crystallographically analyzed. In compound 1, the molecular stacks form a layered structure within the ac plane. In 2, the molecules make a columnar stack along the a axis. In 3, the molecules have a dimeric form and the dimers make a one-dimensional stack along the b axis.The all compounds make a columnar stack, but conformation at nicotinic ester part is found to have a crucial role for molecular arrangement. The gauche conformation at nicotinic ester part (1 and 2) makes an intermolecular p–p interaction between the pyridine groups. This interaction between the stacks prevents an independent molecular stack in 1, and the interaction within the stack in 2 makes larger inclination angles than the ideal one for solid-state polymerization of diacetylenes. The anti conformation in 3, caused by N-H···N hydrogen-bonded dimer, makes it enable to stack one-dimensionaly with a moderate inclination angle, which is favorable for the polymerization.