Double π-Extended Helicene Derivatives Containing Pentagonal Rings: Synthesis, Crystal Analyses, and Photophysics.

Two novel double π-extended [n]helicene (n = 5, 6) derivatives (7b and 9) including pentagonal rings have been synthesized and characterized. Both of them have three isomers containing two enantiomers (P6), (M6), and a diastereoisomer in a meso form (P,M). X-ray single crystal analyses suggest that molecules 7b and 9 exhibit offset packing models of (P6,P5)- and (M6,M5)-isomers. Optical resolution of the resultant compound 7b was finished, and their chiroptical properties, as well as the DFT calculations, were also examined.