Ultra-Fast Molecular Rotors within Porous Organic Cages.

Using variable temperature H static NMR spectra and C spin-lattice relaxation times (T ), we show that two different porous organic cages with tubular architectures are ultra-fast molecular rotors. The central para-phenylene rings that frame the "windows" to the cage voids display very rapid rotational rates of the order of 1.2-8×10  Hz at 230 K with low activation energy barriers in the 12-18 kJ mol range.