1. a School of Chemistry, University of Exeter , Stocker Road, EXETER , EX4 4QD , UK
2. b EPSRC Crystallographic Service, Department of Chemistry , University of Southamton , Highfield, SOUTHAMPTON , SO17 1BJ , UK
3. c Professor Duncan W Bruce, School of Chemistry, University of Exeter , Stocker Road, EXETER , EX4 4QD , ENGLAND Phone: Fax: E-mail: