1. Theoretical Chemistry Laboratory, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, B-5000 Namur, Belgium
2. Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy
3. School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, 700032 Kolkata, India