1. Centre
for Supramolecular Chemistry Research, Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
2. Department
of Chemical Technology, Faculty of Science and Technology, Midlands State University, Private Bag 9055 Senga Road, Gweru, Zimbabwe
3. Department
of Chemistry, University of Buea, Cameroon, PO Box 63, Buea, Cameroon