Acknowledgments
H. S. P. Rao thanks University Grants Commission (UGC) Special Assistance Program (SAP) and Fund for Improvement of Science and Technology Infrastructure in Universities and Higher Educational Institutions (FIST), Department of Science and Technology for financial assistance. CG thanks UGC for Meritorious Fellowship. We thank Central Instrumentation Facility, Pondicherry University, Organic Chemistry Department, Indian Institute of Science, Bangalore and Indian Institute of Technology, Chennai, for recording the spectra and providing the analysis data.