Tamara D. Hamilton

Supramolecular Control of Reactivity in the Solid State: From Templates to Ladderanes to Metal−Organic Frameworks

We describe how reactivity can be controlled in the solid state using molecules and self-assembled metal-organic complexes as templates. Being able to control reactivity in the solid state bears relevance to synthetic chemistry and materials science. The former offers a promise to synthesize molecules that may be impossible to realize from the liquid phase while also taking advantage of the benefits of conducting highly stereocontrolled reactions in a solvent-free environment (i.e., green chemistry). The latter provides an opportunity to modify bulk physical properties of solids (e.g., optical properties) through changes to molecular structure that result from a solid-state reaction. Reactions in the solid state have been difficult to control owing to frustrating effects of molecular close packing. The high degree of order provided by the solid state also means that the templates can be developed to determine how principles of supramolecular chemistry can be generally employed to form covalent bonds. The paradigm of synthetic chemistry employed by Nature is based on integrating noncovalent and covalent bonds. The templates assemble olefins via either hydrogen bond or coordination-driven self-assembly for intermolecular [2 + 2] photodimerizations. The olefins are assembled within discrete, or finite, self-assembled complexes, which effectively decouples chemical reactivity from effects of crystal packing. The control of the solid-state assembly process affords the supramolecular construction of targets in the form of cyclophanes and ladderanes. The targets form stereospecifically, in quantitative yield, and in gram amounts. Both [3]- and [5]-ladderanes have been synthesized. The ladderanes are comparable to natural ladderane lipids, which are a new and exciting class of natural products recently discovered in anaerobic marine bacteria. The organic templates function as either hydrogen bond donors or hydrogen bond acceptors. The donors and acceptors generate cyclobutanes lined with pyridyl and carboxylic acid groups, respectively. The metal-organic templates are based on Zn(II) and Ag(I) ions. The reactivity involving Zn(II) ions is shown to affect optical properties in the form of solid-state fluorescence. The solids based on both the organic and metal-organic templates undergo rare single-crystal-to-single-crystal reactions. We also demonstrate how the cyclobutanes obtained from this method can be applied as novel polytopic ligands of metallosupramolecular assemblies (e.g., self-assembled capsules) and materials (e.g., metal-organic frameworks). Sonochemistry is also used to generate nanostructured single crystals of the multicomponent solids or cocrystals based on the organic templates. Collectively, our observations suggest that the organic solid state can be integrated into more mainstream settings of synthetic organic chemistry and be developed to construct functional crystalline solids.

Onion-Shell Metal-Organic Polyhedra (MOPs): A General Approach to Decorate the Exteriors of MOPs using Principles of Supramolecular Chemistry

Metal-organic polyhedra with surface-exposed organic groups have been designed. The polyhedra are based on concentric shells of alternating negative-positive-negative charges and have been used to design homochiral hosts.

Coding a coordination-driven self-assembly via a hydrogen bond-directed solid-state synthesis: an unexpected chiral tetrahedral capsule.

An achiral ligand, synthesized in the solid state via a coded hydrogen bond-directed organic synthesis, self-assembles with Cu(II) ions to form a chiral tetrahedral capsule that hosts an anion as a guest.

Self-assembled metal-organic squares derived from linear templates as exemplified by a polydentate ligand that provides access to both a polygon and polyhedron

Di- 1a and tetranuclear 1b metal–organic squares have been obtained from bis- and tetra(pyridyl)cyclobutanes synthesized in the solid state, respectively; for 1b, a cyclobutane with two different metal binding subunits supports the formation of a polygon and polyhedron.

A lanthanide-based helicate coordination polymer derived from a rigid monodentate organic bridge synthesized in the solid state

Tetratopic rctt-tetrakis(4-pyridyl)cyclobutane acts as an angular bifunctional ligand that yields a single-stranded helicate coordination polymer based on a Ln(III) ion.

A metal–organic framework with three cavities based on three-coloured square tiling derived from a cyclobutane constructed in the solid state

The unsymmetrical tetratopic ligand rctt-1,2-bis(3-pyridyl)-3,4-bis(4-pyridyl)cyclobutane self-assembles with zinc(II) nitrate to form a 2D metal–organic framework with three distinct cavities.

Finite molecular assemblies in the organic solid state: toward engineering properties of solids

Abstract Assemblies of organic molecules that form finite structures represent targets for crystal engineers that can exhibit properties largely independent of crystal packing. Such finite molecular assemblies can display function, such as host–guest behavior and chemical reactivity. Here, we provide a review of finite molecular assemblies characterized in the organic solid state. The assemblies are classified as being either purely synthetic or functional. Examples from both the areas are presented and discussed.

Discrete and infinite coordination arrays derived from a template-directed, solid-state, organic synthesisBased on the presentation given at CrystEngComm Discussion, 29th June?1st July 2002, Bristol, UK.

A product derived from a template-directed, organic, solid-state synthesis, rctt-tetrakis(2-pyridyl)cyclobutane (2,2′-tpcb), serves as a bis-chelating ligand upon reaction with Cu(NO3)2·2.5H2O and CuSO4·5H2O to produce discrete and infinite coordination arrays, [Cu2(NO3)4(μ-2,2′-tpcb)] (1) and [Cu2(μ2-SO4)2(μ-2,2′-tpcb)(H2O)2]n·9H2O (2), respectively.