A DFT Study on Push-Pull (Amino-Nitro) Fulminenes and Hexahelicenes

In order to investigate the steric and electronic effects of electron-donor (amino) and -acceptor (nitro) substituents on hexahelicene and fulminene (isomeric and isoarithmic compounds), sixteen different types of terminal-amino-nitro hexahelicenes (H1–H16) and fulminenes (F1–F16) have been designed and investigated theoretically by the DFT method at B3LYP/6-31G(d) level. Besides electronic and thermodynamic properties, aromaticities (via NICS(0) calculations) have also been discussed for the above sets of terminal-rings-substituted hexahelicenes and fulminenes having 16 isomers each. Steric hindrance, seen enhanced in Hn structures, affects the total energies and heat of formations. The quinonoid conjugation is a minor factor in determining the trends in ring aromaticity of the above structures.