Synthesis of fluorocalix[4]arene and estimation of intramolecular CF⋯HO hydrogen bond

• A weak CF⋯HO hydrogen bond was detected in fluorocalix[4]arene.
• The NMR and IR spectroscopies, and crystallographic analysis clearly show the H.B.
• The H.B. patterns in solution and solid states were determined.
• The free energy of the aromatic ring inversion was estimated by VT-NMR studies.

A weak intramolecular CF⋯HO hydrogen bond was detected in fluorocalix[4]arene 1 by using NMR and IR spectroscopies, and crystallographic analysis. This interaction was detected in several molecules; however, the molecular design must be very precise to detect the weak H.B. In this case, H.B. patterns in solution and solid states were determined and the free energy of the aromatic ring inversion was estimated by VT-NMR studies. Based on the aromatic ring inversion potentials of 1, calix[4]arene, and monodeoxycalix[4]arene, the free energy of the CF⋯HO H.B. in this system was estimated.

Fluorocalix[4]arene was synthesized and the CF⋯HO hydrogen bond was detected by 1H, 19F NMR and IR spectroscopies and crystallographic analysis. Hydrogen bond patterns in the lower rim in the solid and solution states were discussed. The bonding energy of the CF⋯HO hydrogen bond in this system was estimated.Figure optionsDownload as PowerPoint slide