Acknowledgment
The authors are thankful to The Chairman, Department of Chemistry, A.M.U. Aligarh for providing the necessary facilities to carry out this research work. The PURSE and FIST grants from DST and SAP DRS-II grant from UGC are acknowledged. One of the authors (S.K.) gratefully acknowledged to UGC, New Delhi for awarding Maulana Azad National Fellowship (MANF).