Crystal structure of and conformational equilibria in 1,1′-dihydroxybis(4H-cyclopenta[def]phenanthrene) and related derivatives

✍ Scribed by Mary Hoang; Gabriela Mladenova; Alan C. Hopkinson; Jailal Ramnauth; Edward Lee-Ruff

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 128 KB
• Volume: 39
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.839

✦ Synopsis

Abstract

The aromatic protons and carbons in the NMR spectra of certain clamped 1,1,2,2‐tetraarylethane‐1,2‐diols undergo intermediate exchange at ambient temperature as the result of conformational equilibrium between two enantiomeric gauche forms. The crystal structures for two of these derivatives show the conformational preference for this geometry in the solid state in contrast to other reported unclamped 1,1,2,2‐tetraarylethane‐1,2‐diols. The conformational preference of these vicinal diols parallels that for the 1,1,2,2‐tetraarylethanes. However, in the asymmetrically substituted diphenylmethylfluorene series, the vicinal diol prefers to adopt a gauche conformation in contrast to the hydrocarbon which prefers the anti geometry attributed to hydrogen bonding effects in the former. The results of AM1 calculations for the conformational preferences of this series of diols and ethanes are included and agree with experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.