1. Department of Chemistry, University of the Free State (Qwa-Qwa), Private Bag X13, Phuthaditjhaba, 9866, South Africa, School of Chemistry and Biochemistry, Potchefstroom University, Private Bag 6001, Potchefstroom, 2520, South Africa, and Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro