1. a Department of Chemistry , Florida Atlantic University , 500 N.W. 20th Street, P. O. Box 3091, Boca Raton , FL , 33431-0991 , U.S.A.
2. b Department of Chemistry , Faculty of Science, Ain Shams University , Abbassia , Cairo , Egypt
3. c Institut de Topologie et de Dynamique des Systèmes , (associá au C.N.R.S. -URA 34), Universitá Paris 7, 1, rue Guy de la Brosse, F-75005 , Paris , France
4. d Dápartement de Chimie , Facultá des Sciences, Universitá C. A. Diop , Dakar , Sénégal