Synthesis, spectral studies and antibacterial activity of iron(III) complexes with hydrazone functionalized ligands: X-Ray structure determination of a novel five coordinate complex containing labile ligands

Iron(III) complexes having general formula FeLCl2 [where, L = 2-acetylpyridine acetoylhydrazone (APAH), 2-acetylpyridine benzoylhydrazone (APBH), 2-acetylthiophene acetoylhydrazone (ATAH), and 2-acetythiophene benzoylhydrazone (ATBH)] have been synthesized and characterized based on molar conductivity, electronic and IR spectroscopy. The structure of iron(III) complex with APBH ligand is determined using single crystal X-ray crystallography. The complex crystallizes in monoclinic space group P21/n with a = 7.8490(6) angstrom, b = 15.1018(11) angstrom, c = 13.2263(10) angstrom, alpha = 90 degrees, beta=100.183(3)degrees, gamma = 90 degrees, V = 1543.1(2) angstrom(3) and Z = 4 with central Fe(III) ion coordinated by one tridentate APBH ligand. The iron is involved in 5-coordinate bonding with one organic (hydrazone) unit and two labile chloride ligands. The ligand acts as NNO-tridentate donor system. Iron is coordinated to pyridine ring nitrogen, azomethine nitrogen and benzoyl oxygen atoms and the two chloride ligands bind with metal completing distorted square pyramidal structure. The ligands and iron complexes are screened for their anti-bacterial activities against Pseudomonas aureoginos and Bacillus cereus. Among ligands, acetoyl hydrazones show more activity than the corresponding benzoyl hydrazones. The hydrazones having a methyl/and pyridine groups show higher antibacterial activity. The iron complexes show higher activity than the metal free ligands.