Crystal engineering

Crystal engineering studies the design and synthesis of solid-state structures with desired properties through deliberate control of intermolecular interactions.

[3] The term 'crystal engineering' was first used in 1955 by R. Pepinsky [4] but the starting point is often credited to Gerhard Schmidt[5] in connection with photodimerization reactions in crystalline cinnamic acids.

Since this initial use, the meaning of the term has broadened considerably to include many aspects of solid state supramolecular chemistry.

Crystal engineering relies on noncovalent bonding to achieve the organization of molecules and ions in the solid state.

[8] Molecular self-assembly is at the heart of crystal engineering, and it typically involves an interaction between complementary hydrogen bonding faces or a metal and a ligand.

"Supramolecular synthons" are building blocks that are common to many structures and hence can be used to order specific groups in the solid state.

[11] The formation (often referred as molecular self-assembly depending on its deposition process) of such architectures lies in the use of solid interfaces to create adsorbed monolayers.

While long-range strong intermolecular interactions dictate the formation of kinetic crystals, the close packing of molecules generally drives the thermodynamic outcome.

A major advance in the CSP happened in 2007 while a hybrid method based on tailor made force fields and density functional theory (DFT) was introduced.

Crystal engineering principles have been applied to the design of non-linear optical materials, especially those with second harmonic generation (SHG) properties.

[27] For example, long chains or layers of acetaminophen molecules form due to the hydrogen bond donors and acceptors that flank the benzene ring.

[32] Crystallographic methods, such as X-ray diffraction, are used to elucidate the crystal structure of a material by quantifying distances between atoms.

Microscopic methods, such as optical, electron, field ion, and scanning tunneling microscopy, can be used to visualize the microstructure, imperfections, or dislocations of a material.

[33] Calorimetric methods, such as differential scanning calorimetry, use induce phase transitions in order to quantify the associated changes in enthalpy, entropy, and Gibb's free energy.

An example of crystal engineering using hydrogen bonding reported by Wuest and coworkers in J. Am. Chem. Soc. , 2007, 4306–4322.
Br···O halogen bonds observed in crystal structure of 3D silsesquioxanes. [ 7 ]
A five component crystal was designed by Desiraju and co workers by a rational retrosynthetic strategy ( IUCrJ , 2016, 3, 96–101).
The pathways to kinetically favoured and thermodynamically favoured crystals.
A resorcinol based templating strategy described by Macgillivray and co workers to illustrate the control of photodimerization outcome, J. Am. Chem. Soc. , 2000, 122, 7817-7818.
Four mechanical properties of crystalline materials: shear strength, plasticity, elasticity, and brittleness. Information adapted from Saha et al. 2018. [ 21 ]
Designing a material with targeted mechanical properties requires command over complex structures across a range of length scales.
A. Slip planes associated with layered or columnar architectural features in crystalline materials. Red dotted and black dashed lines represent the direction of the weakest and strongest intermolecular interactions, respectively, which influences the slip plane. B. Example of the strongest (hydrogen bonds) and weakest (van der Waals) interactions in acetaminophen structure that influences the crystal structure.