1. Department of Chemistry Indian Institute of Technology Bombay Powai, Mumbai 400076 India
2. Theoretical Chemistry Section Bhabha Atomic Research Centre Mumbai 400085 India
3. Present address: Bio-Science Group Bhabha Atomic Research Centre Mumbai 400085 India
4. Department of Chemistry Indian Institute of Science Education and Research Kolkata, Mohanpur Nadia 741246 India
5. Department of Chemistry Ashoka University Sonepat, Haryana 131029 India