Effect of the position of cyano group on molecular recognition, supramolecular super helix architecture and spontaneous resolution of aza[7]helicenes

Five derivatives of cyano-containing 9-alkyl-9H-aza[7]helicene were synthesized and their behavior in the crystallization was investigated. Only one of the derivatives, 5,13-dicyano-9-butyl-9H-aza[7]helicenes, showed the phenomenon of spontaneous resolution, which was attributed to the conglomerate formation of the same helical isomer via CN···H–Ar interaction. The helical molecules with same chiral description were aligned to form a necklace-like chain of secondary superhelix architecture of the same chirality. A correlation of the position of the cyano group and spontaneous resolution phenomena has been derived.