1. Institut für Physikalische Chemie der Universität Halle-Wittenberg, FB Chemie Merseburg, Geb. 123, D-06099 Halle, Germany; Central Research Institute for Chemistry, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary; and Department of Chemistry, Gy. J. Teachers' Training College, H-6701 Szeged P.O. Box 396, Hungary