Metal Complexes of Heterocyclic Hydrazone Schiff-Bases: Preparation, Spectral Characterisation and Biological Study

New isatinic hydrazone Schiff-base ligands, namely furan-2-carboxylic acid (2-oxo-1,2-dihydro-indol-3-ylidene)-hydrazide (L 1 ), thiophene-2-carboxylic acid (2-oxo-1,2-dihydro-indol-3-ylidene)-hydrazide (L 2 ) and 2-(pyridine-2-yl-hydrazono)-1,2-dihydro-indol-3-one) (L 3 ) are reported. The ligands were prepared by the condensation of furan-2-carboxylic acid hydrazide (L 1 ), thiophene-2-carboxylic acid hydrazide (L 2 ), and 2-hydrazino pyridine (L 3 ) with isatine. Monomeric complexes were prepared from the reaction of the corresponding metal chloride with the ligands. The ligands and their nine new complexes of the general formulae [M(L n ) 2 ]Cl 2 [where M = Co(II), Zn(II) and Cd(II); n = L 1 , L 2 and L 3 ] were characterised by spectroscopic methods (FTIR, UV–Vis, 1 H, 13 C NMR), elemental analysis, metal content, magnetic measurement and molar conductance. These studies revealed the formation of six coordinate complexes, in which the geometry about metal atom is a distorted octahedral. Biological activity of the ligands and their metal complexes against Gram-positive bacterial strain Bacillus (G + ) and Gram-negative bacteria Ecoli (G − ) are evaluated. The effects of prepared compounds depend on the type of tested bacteria. It is clear that the ligands and their metal complexes have a potential effect on the Gram-positive (G + ) and Gram-negative (G − ) strains of the tested bacteria.