Syntheses, Structural\nAnalyses, and Properties of\nCondensed Arenes with Multihelicity

A <i>C</i><sub>1</sub>-symmetric hexapole helicene\n(HH)\nand a <i>C</i><sub>3</sub>-symmetric dodecapole helicene\n(DH) were prepared, and their three-dimensional structures were verified\nby X-ray crystallography and density functional theory calculations.\nThe molecular geometries and local helical configurations of their\nmost stable diastereomers were correctly predicted by arranging suitable\nconformations of the peripheral aryl rings. Importantly, the outermost\nthree [5]helicenes with a consistent configuration in DH were observed\nto increase the thermostability, enantiomerization barrier (Δ<i>H</i><sup>⧧</sup> = 40.5 kcal/mol), specific rotation\n([α]<sub>24</sub><sup>D</sup> = −4228°) and absorption dissymmetry factor (<i>g</i><sub>abs</sub> = 1.35 × 10<sup>–3</sup> at\n453 nm).