Syntheses, Structural Analyses, and Properties of Condensed Arenes with Multihelicity

A <i>C</i>₁-symmetric hexapole helicene (HH) and a <i>C</i>₃-symmetric dodecapole helicene (DH) were prepared, and their three-dimensional structures were verified by X-ray crystallography and density functional theory calculations. The molecular geometries and local helical configurations of their most stable diastereomers were correctly predicted by arranging suitable conformations of the peripheral aryl rings. Importantly, the outermost three [5]helicenes with a consistent configuration in DH were observed to increase the thermostability, enantiomerization barrier (Δ<i>H</i>^⧧ = 40.5 kcal/mol), specific rotation ([α]₂₄^D = -4228°) and absorption dissymmetry factor (<i>g</i>_abs = 1.35 × 10^-3 at 453 nm).