Synthesis of π-extended aza[5]helicene bearing AuI-acetylide at the outside or the inside of the helix

[Display omitted] The AuI complexes with π-extended aza[5]helicenes either at the external or at the internal positions of the helix have been successfully synthesized. The electrochemical analysis revealed the coordination of AuI ions lifted HOMO, and also the reduction of HOMO-LUMO gap on complexation were confirmed by optical analysis. Both complexes exhibited quenching of emission compared to the corresponding ligand. Theoretical analysis revealed slight contribution of d orbital would cause acceleration of intersystem-crossing in both cases. Furthermore, the lack of orbital overlap between ligands at LUMO of the internal AuI complex due to steric hindrance caused the different optical behaviors between two complexes.