Crystal engineering of co-crystals and their relevance to pharmaceuticals and solid-state chemistry

Abstract

The field of crystal engineering has evolved in such a manner that it has become synonymous with synthesis of new classes of organic and metal-organic compounds. Crystal engineering invokes selfassembly of existing molecules or ions and therefore means that a wide range of new compounds can be generated without the need to invoke covalent bond breakage or formation. This presentation will address a long-known but little studied class of compound,co-crystals, and it will highlight their relevance to pharmaceutical science and solid-state chemistry. The presentation will be organized as follows: A general introduction to the when, how and why of co-crystals with emphasis upon the hierarchy of hydrogen bonds that can be exploited to design co-crystals from first principles; Pharmaceuticals are perhaps the most valuable materials known to mankind and there are important intellectual property, regulatory and efficacy implications if one is able to discover new compositions of matter for active pharmaceutical ingredients (APIs). Emphasis will be placed upon pharmaceutical co-crystals, a long known but little explored alternative to more widely accepted forms of API such as polymorphs, solvates, salts; The potential impact of co-crystals on green strategies for the synthesis/processing of fine chemicals such as APIs and novel ligands for nanoscale polyhedra and their networks will be discussed with emphasis upon co-crystal controlled solid-state synthesis (C3S3); The use of co-crystals involving homochiral co-crystal formers for resolution of enantiomers will be discussed.