Charge "mis-matched" hydrogen bonded frameworks for cation exchange and dye sorption.

Anionic hydrogen bonded frameworks were synthesised from di or tetra-amidinium hydrogen bond donor components and a charge "mis-matched" tecton possessing a 5- charge but only four hydrogen bond accepting groups. The net negative charge on the framework skeletons necessitates the presence of a cation in the framework channel. In one of the frameworks, the initially incorporated organic cation was rapidly displaced by smaller inorganic cations, or the cationic dye methylene blue. This facilitated the effective and selective removal of this dye from water.

Assembly and Covalent Cross-Linking of an Amine-Functionalised Metal-Organic Cage.

The incorporation of reactive functional groups onto the exterior of metal-organic cages (MOCs) opens up new opportunities to link their well-defined scaffolds into functional porous solids. Amine moieties offer access to a rich catalogue of covalent chemistry; however, they also tend to coordinate undesirably and interfere with MOC formation, particular in the case of Cu2 paddlewheel-based MOCs. We demonstrate that tuning the basicity of an aniline-functionalized ligand enables the self-assembly of a soluble, amine-functionalized Cu4L4 lantern cage (1). Importantly, we show control over the coordinative propensity of the exterior amine of the ligand, which enables us to isolate a crystalline, two-dimensional metal-organic framework composed entirely of MOC units (2). Furthermore, we show that the nucleophilicity of the exterior amine of 1 can be accessed in solution to generate a cross-linked cage polymer (3) via imine condensation.

Self-sorting of porous Cu4L2L'2 metal-organic cages composed of isomerisable ligands.

We report the self-sorting of a dynamic combinatorial library (DCL) of metal-organic cages composed of a rotationally isomerisable ligand. Convergence of the DCL occurs upon crystallisation and leads to low-symmetry Cu4L2L'2 cages that display differing porosities based on their overall shape and ligand configuration.

Linking metal-organic cages pairwise as a design approach for assembling multivariate crystalline materials.

Using metal-organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal-organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu4L4 and Rh4L4 MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities.

Biomimetic synthetic studies on meroterpenoids from the marine sponge Aka coralliphaga: Divergent total syntheses of siphonodictyal B, liphagal and corallidictyals A-D.

The marine sponge Aka coralliphaga is a rich source of biologically active and structurally interesting meroterpenoids. Inspired by these natural products, we have used biosynthetic speculation to devise biomimetic syntheses of siphonodictyal B, liphagal and corallidictyals A-D from sclareolide. This work resulted in the development of new cascade reactions in the synthesis of liphagal, the reassignment of the structure of siphonodictyal B, and the realisation that corallidictyals A and B are possibly isolation artefacts.

Some chemical speculation on the biosynthesis of corallidictyals A-D.

The efficient conversion of siphonodictyal B into the spirocyclic natural products corallidictyals A-D has been achieved via oxidative and acid catalyzed cyclizations. The oxidative cyclization of siphonodictyal B occured spontaneously under aerobic oxidation conditions, which suggests that corallidictyals A and B are possibly artefacts of the isolation process. The mechanism of the oxidative cyclization of siphonodictyal B could be described as either an anionic 5-endo-trig cyclization (which is formally disfavoured by Baldwin's rules), or as an electrocyclic reaction, of an ortho-quinone intermediate.

Total Synthesis and Structure Revision of (-)-Siphonodictyal B and Its Biomimetic Conversion into (+)-Liphagal.

The structure of siphonodictyal B has been reassigned on the basis of the total synthesis of both possible C-8 epimers. The revised structure of siphonodictyal B was converted into liphagal by acid catalyzed rearrangement of a proposed epoxide intermediate. This biomimetic cascade features a succession of four distinct reactions (epoxidation, o-quinone methide formation, ring expansion, and benzofuran formation) that occur in a one-pot operation under mild conditions. During these studies we also isolated a surprisingly stable o-quinone methide that supports our mechanistic proposal for liphagal biosynthesis.