Understanding gas capacity, guest selectivity, and diffusion in porous liquids.

Porous liquids are a new class of material that could have applications in areas such as gas separation and homogeneous catalysis. Here we use a combination of measurement techniques, molecular simulations, and control experiments to advance the quantitative understanding of these liquids. In particular, we show that the cage cavities remain unoccupied in the absence of a suitable guest, and that the liquids can adsorb large quantities of gas, with gas occupancy in the cages as high as 72% and 74% for Xe and SF6, respectively. Gases can be reversibly loaded and released by using non-chemical triggers such as sonication, suggesting potential for gas separation schemes. Diffusion NMR experiments show that gases are in dynamic equilibrium between a bound and unbound state in the cage cavities, in agreement with recent simulations for related porous liquids. Comparison with gas adsorption in porous organic cage solids suggests that porous liquids have similar gas binding affinities, and that the physical properties of the cage molecule are translated into the liquid state. By contrast, some physical properties are different: for example, solid homochiral porous cages show enantioselectivity for chiral aromatic alcohols, whereas the equivalent homochiral porous liquids do not. This can be attributed to a loss of supramolecular organisation in the isotropic porous liquid.

Spatially resolved multicomponent gels.

Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this 'self-sorted network' is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

The effect of self-sorting and co-assembly on the mechanical properties of low molecular weight hydrogels.

Self-sorting in low molecular weight hydrogels can be achieved using a pH triggered approach. We show here that this method can be used to prepare gels with different types of mechanical properties. Cooperative, disruptive or orthogonal assembled systems can be produced. Gels with interesting behaviour can be also prepared, for example self-sorted gels where delayed switch-on of gelation occurs. By careful choice of gelator, co-assembled structures can also be generated, which leads to synergistic strengthening of the mechanical properties.

Adding the right (or left) twist to tris-chelate complexes--coordination chemistry of chiral oxazolylphenolates with M3+ ions (M = Al or lanthanide).

A series of homoleptic tris-chelate complexes ML3 (M = Al or rare earth; L = chiral or achiral oxazolyl phenolate or -naphtholate) is reported. In all cases, complexes crystallize as mer-isomers and complete diastereoselectivity is observed on crystallization of the complexes: ML3 crystallize with Λ-helicity at the metal where L = (S)-oxazolylphenolate. Complexes have been characterized in solution by NMR spectroscopy, demonstrating rapid ligand exchange at ambient temperature for rare earth complexes, and slow exchange on the NMR timescale for complexes of Al; in all cases the mer-isomer is observed exclusively. Crystal structures are reported for [YL3]2 (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-phenolate), mer-[YbL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate) and mer-[AlL3] (L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-methylphenolate, L = (S)-2-(4-isopropyl-4,5-dihydrooxazol-2-yl)-6-cyanophenolate), L = (S)-1-(4-isopropyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate, L = 1-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)naphthalen-2-olate).

In silico design of supramolecules from their precursors: odd-even effects in cage-forming reactions.

We synthesize a series of imine cage molecules where increasing the chain length of the alkanediamine precursor results in an odd-even alternation between [2 + 3] and [4 + 6] cage macrocycles. A computational procedure is developed to predict the thermodynamically preferred product and the lowest energy conformer, hence rationalizing the observed alternation and the 3D cage structures, based on knowledge of the precursors alone.