Theoretical and spectroscopic studies of 5-fluoro-isatin-3-( N-benzylthiosemicarbazone) and its zinc(II) complex

Abstract

The molecular parameters (bond lengths, bond angles, the highest occupied molecular orbital energy ( E HOMO), lowest unoccupied molecular orbital energy ( E LUMO), the energy gap between E HOMO and E LUMO (Δ E HOMO–LUMO), dipole moment, charges on the atoms of 5-fluoro-isatin-3-( N-benzylthiosemicarbazone)) (H 2FLB) as monomer were studied by HF and B3LYP methods using several basis sets. The cyclic trimer form of H 2FLB was also reproduced. The new zinc(II) complex with H 2FLB has been synthesized and characterized using elemental analysis, Fourier transform infrared spectroscopy (FT-IR), UV and 1H NMR spectra. Theoretical calculations have also been performed by HF method using 6-31G(d,p) and LanL2DZ basis sets. The assignments of bands observed in FT-IR spectrum for H 2FLB and its Zn(II) complex have been made using ab initio and DFT methods. Some significant differences in vibrational structures between ligand and Zn(HFLB) 2 have been observed and discussed.