Reactions Between or Within Molecular Crystals

• Published in: Angewandte Chemie (International ed.) Vol. 43; no. 31; pp. 4002 - 4011
• Main Authors: Braga, Dario, Grepioni, Fabrizia
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 06.08.2004; WILEY‐VCH Verlag
• Subjects: crystal engineering; mechanochemistry; solid-state reactivity; solventless reactions; supramolecular chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.200301721

Reactions that occur within or between molecular crystals, in particular those reactions that are activated by mechanical methods, are reviewed. The focus is on processes (whether intrasolid or intersolid) that are controlled primarily by supramolecular bonding, such as template cycloadditions, formation of inclusion compounds, reactions between molecular crystals by the reassembling of noncovalent bonds, and the formation of complexes and coordination compounds. It is proposed that solvent‐free mechanochemical methods, for example, cogrinding, milling, and kneading, represent viable “green” routes for the preparation of novel molecular and supramolecular solids. Weaning chemistry onto solids: reactions between solids (see picture) are often regarded as oddities and mechanical synthetic methods are felt to be fundamentally “nonchemical”. This attitude is changing as solvent‐free conditions become more important in environmentally friendly processes. In addition, solid‐state synthetic procedures are often viable alternative routes to known products and also to new compounds not obtainable by traditional solution chemistry.