1. Department of Chemistry, University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy, Theoretical Chemistry Section, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands, Science and Technology Facilities Council Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX United Kingdom, and Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, South-Korea