1. Dipartimento di Chimica, Università della Basilica, Via N. Sauro 85, 85100 Potenza, Italy
2. Dep. of Chemistry, Pohang Univ. of Science and Technology, Pohang 790-784, South-Korea
3. Theoretische Chemie, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands