Zinc complexes of hydrazone derivatives bearing 3,4-dihydroquinolin-2(1H)-one nucleus as new anti-tubercular agents

Abstract

A series of hydrazone derivatives 5a–5i were synthesized through multi-step reactions. The 2-(2-oxo-1,2,3,4-tetrahydroquinoline-7-yloxy)acetohydrazide was prepared from 7-hydroxy-3,4-dihydroquinolin-2(1H)-one as starting material. Then the condensation of 2-(2-oxo-1,2,3,4-tetrahydroquinoline-7-yloxy)acetohydrazide with different o-hydroxyaldehyde derivatives 4a–4i yielded into hydrazone derivatives 5a–5i. These hydrazone ligands were complexed with Zn (II) yielded complexes 6a–6i. The molecular structures of the hydrazones 5a–5i and Zn (II) complexes 6a–6i were characterized by FTIR, 1H and 13C NMR, LCMS, XRD, DSC-TGA, UV–Visible, Fluorescence and elemental analysis. The conductivity experiments showed that all the complexes are non-electrolytes.The Preliminary results of antituberculosis study showed that most of the Zn (II) complexes 6a–6i demonstrated very good antituberculosis activity while the ligands 4a–4i showed moderate activity. Among the tested compounds 6c, 6e and 6h were found to be most active with minimum inhibitory concentration (MIC) of 1.6 μg/mL against Mycobacteriumtuberculosis (H37 RV strain) ATCC No.-27294 which is comparable to ‘‘first and second line’’ drugs used to treat tuberculosis. Keywords: Hydrazone, Ligand, Metal complex, Anti-tuberculosis, Fluorescence