Dynamics in Flexible Pillar[]arenes Probed by Solid-State NMR.

Pillar[]arenes are supramolecular assemblies that can perform a range of technologically important molecular separations which are enabled by their molecular flexibility. Here, we probe dynamical behavior by performing a range of variable-temperature solid-state NMR experiments on microcrystalline perethylated pillar[]arene ( = 5, 6) and the corresponding three pillar[6]arene xylene adducts in the 100-350 K range. This was achieved either by measuring site-selective motional averaged C H heteronuclear dipolar couplings and subsequently accessing order parameters or by determining H and C spin-lattice relaxation times and extracting correlation times based on dipolar and/or chemical shift anisotropy relaxation mechanisms.

Melting of hybrid organic-inorganic perovskites.

Several organic-inorganic hybrid materials from the metal-organic framework (MOF) family have been shown to form stable liquids at high temperatures. Quenching then results in the formation of melt-quenched MOF glasses that retain the three-dimensional coordination bonding of the crystalline phase. These hybrid glasses have intriguing properties and could find practical applications, yet the melt-quench phenomenon has so far remained limited to a few MOF structures.

Near-Ideal Xylene Selectivity in Adaptive Molecular Pillar[ n]arene Crystals.

The energy-efficient separation of alkylaromatic compounds is a major industrial sustainability challenge. The use of selectively porous extended frameworks, such as zeolites or metal-organic frameworks, is one solution to this problem. Here, we studied a flexible molecular material, perethylated pillar[ n]arene crystals ( n = 5, 6), which can be used to separate C8 alkylaromatic compounds.

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.