Leeds Centre for Crystallization

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Crystal Engineering and Porous Materials

Crystal engineering is the design and synthesis of well ordered solid state materials from molecular or ionic components using intermolecular interactions.

The ultimate aim is to control the orientation of molecules as they form a crystal lattice in order to control properties and function of the material.

Crystal engineering relies on a knowledge and understanding of how supramolecular and other relatively labile interactions can be manipulated to produce materials with desired properties. Hydrogen bonding, ∏-∏ stacking, halogen bonding and metal-ligand coordination are the most commonly used interactions. Molecular or ionic building blocks are termed tectons, and these are designed to self-assemble into a crystalline material with a desired structure. Coordination polymers, for example, use the stereochemical preferences of transition metals combined with multifunctional organic ligands to generate materials with polymeric 1D, 2D or 3D structures.

Crystal engineering principles are also being used to investigate and understand polymorphism.

A number of different functionalities or applications can be targeted through crystal engineering. These include applications where control over the orientation of molecular components is crucial such as in non-linear optics, applications where having an ordered array of metal cations is important such as in magnetic materials including spin crossover materials as switching devices, and polymorphism in pharmaceuticals. However, the area that has received most attention is using crystal engineering to create new types of porous materials. 3D coordination polymers with scaffolding-like structures that contain pores and channels, and where the network does not collapse on de-solvation are often termed metal-organic frameworks (MOFs).

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