π-Curved Blatter radicals: Blatter helicenes

Abstract

Photocyclization of 8-aryloxy-3-phenylbenzo[<i>e</i>][1,2,4]triazines leads to π-delocalized helicene radicals 1[n] (<i>n</i> = 5, 6, 7) containing the ring-fused 1,4-dihydro[1,2,4]triazin-4-yl as a spin source. Single crystal XRD revealed that the photocyclization to 1[n] involves a Smiles rearrangement. Radicals 1[n] were investigated by spectroscopic, electrochemical and DFT methods, while racemic helicene 1[7] was resolved and ECD spectra were recorded.