New functional hexahelicenes - Synthesis, chiroptical properties, X-ray crystal structures, and comparative data bank analysis of hexahelicenes

Seven new hexahelicenes (3-7, 9, 10) containing different functional group substituents have been synthesized and, in three cases (4, 8, 10), optically resolved. Optical rotations were measured and CD spectra are reported. X-ray crystal structures of the helicenes 1, 3, 4, 8, and 9 have been determined, of which 4 represents a 1:1 clathrate with acetone. These show a concerted interplay of C-H...O C-H...pi, and pi...pi supramolecular interactions in the packings, mostly yielding stacks of molecules (1, 3, 4, 8). Statistical analysis of the molecular dimensions in these and related crystal structures was carried out in order to identify potential parameters relevant to macroscopic phenomena, including optical rotation. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).