1. Department of Chemistry, Faculty of Science, The University of Maroua, PO Box 814, Maroua, Cameroon
2. Department of Chemistry, Faculty of Science Semlalia, University of Cady Ayyad, Marrakech, Morocco
3. Department of Chemistry, Higher Teacher Training College Bertoua, The University of Bertoua, PO Box 652, Bertoua, Cameroon
4. Physical and Theoretical Chemistry Laboratory, Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon