1. Department of Applied ChemistryUniversity of Johannesburg P. O. Box 17011 Doornfontein Campus, 2028 Johannesburg South Africa.
2. Department of ChemistryFaculty of ScienceObafemi Awolowo University Ile-Ife 220005 Nigeria.
3. Council for Scientific and Industrial ResearchMeraka InstituteCentre for High Performance Computing 15 Lower Hope Road, Rosebank Cape Town 7700 South Africa.