1. Department of Chemistry, University of Cape Town, Rondebosch 7701, Cape Town, South Africa, Fax: +27‐21‐6505195, http://www.gregsmith‐research.co.za
2. Scientific Computing Research Unit and chemistry Department, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
3. Department of Chemistry and Polymer Science, Stellenbosch University, Matieland 7602, South Africa