Small-molecule chemical crystallography–from three to four dimensions: a personal perspective

Abstract

The instrumentation and methodology associated with chemical crystallography has developed extensively over the last 25 years. Data collection times have been reduced from days to hours and even minutes as serial diffractometers have been replaced by area detector systems. The increase in reliability of rotating anode generators and the advent of synchrotron radiation has meant that the available X-ray flux has increased by factors of between 100 to 10,000. These advances coupled with the development of new cryogenic systems and high pressure cells has allowed a range of new types of crystallographic experiment to be undertaken that had not been possible previously. One area that has benefited from these advances is stroboscopic photocrystallography, where it is possible to determine the structure of molecules in a crystalline environment that have lifetimes of only a few microseconds or to monitor reactions as they occur in real time. These experiments originate from technical easier experiments, which include studies of metastable structural states and solid state phase transition. As photocrystallographic techniques in small molecule crystallography develop further it is expected that it will be possible to determine the structures of species that have lifetimes of the order of only nanoseconds.

Keywords:

• Single crystal X-ray crystallography
• Synchrotron
• Small molecule crystallography
• Diffractometers
• Detectors
• Photocrystallography

Acknowledgements

On a personal level, I would like to take this opportunity to thank all those who have helped me to develop my interest in crystallography. Particular thanks go to Mike Hursthouse and George Sheldrick who sparked and nurtured my interest in the subject. I would also like to thank all the members of the Raithby group over the last thirty years for all their hard work and support. Those who have worked on the photocrystallography project during the last few years deserve a special mention. Drs Louise Male, Li-ling Ooi, Hazel Sparkes, Alex Griffin and Ms Teresa Savarese from my group have all contributed enormously as have Drs Jacqui Cole, Katharine Bowes, and Shamus Husheer, from Cambridge, and the Daresbury Station Scientists, Simon Teat and John Warren. I am also most grateful to Philip Coppens, Michael Wulff, Simone Techert and John Helliwell for many very valuable discussions.