1. Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon
2. Department of Chemistry, Faculty of Science, The University of Bamenda, P.O. Box 39, Bambili, Bamenda, Cameroon
3. Département de Chimie, Faculté des Sciences, Université de Douala, Douala, Cameroon
4. Sophisticated Analytical Instruments Facility, Indian Institute of Technology, Madras, Chennai 600036, India
5. Department of Organic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon