9‐Fluoro‐18‐hydroxy‐[3.3]metacyclophane: Synthesis and Estimation of a C−F···H−O Hydrogen Bond

Abstract

Abstract A cyclophane composed of fluorobenzene and phenol units was synthesized in order to observe the C−F ··· H−O hydrogen bond. In the crystal structure, 20% of the molecule clearly shows the intramolecular hydrogen bond and the other 80% is free from hydrogen bonding. On the other hand, a distinct low‐field shift of the phenolic OH proton was observed in the 1 H NMR spectrum compared to that of the F‐free analog. Furthermore, O−H ··· F through‐space coupling was observed. From the results of the crystallographic analysis, IR, and NMR spectra, the C−F ··· H−O hydrogen bond energy of this system was estimated to be 0.84−3.7 kJ·mol −1 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)