1. Department of Chemistry, Rhodes University, P.O. Box 94, Makhanda, Grahamstown 6139, South Africa
2. Department of Chemistry, University of Pretoria, 02 Lynnwood Road, Hatfield, Pretoria 0002, South Africa
3. Department of Chemistry, Nelson Mandela University, P.O. Box 77000, Summerstrand, Gqeberha, Port Elizabeth 6031, South Africa
4. School of Chemistry and Physics, University of Kwa-Zulu Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa
5. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050 Johannesburg, South Africa
6. Faculty of Pharmacy, Rhodes University, P.O. Box 94, Makhanda, Grahamstown 6139, South Africa