1. Contribution from the Department of Chemistry, Faculty of Science, Shizuoka University, Ohya, Shizuoka 422-8529 Japan, Dipartimento di Chimica “G. Ciamician”, Università degli Studi di Bologna, Via Selmi 2, I-40126 Bologna, Italy, and Departamento de Química-Física, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain