Studies on synthesis, characterisation, molecular modeling and antimicrobial activity of some metal chelates of pyrazolone based ligands

Some novel complexes of the ligands N-(3-methyl 1-thiocarbamyl-5-oxo-2-pyrazolin-4-ylene)-N'-(4'-antipyrine) hydrazine (HATP) and N-(3-methyl-1-thiocarbamyl-5-oxo-2-pyrazolin-4-ylene)-N-1-(4(1)-benzothiazole) hydrazine (HBTP) with Mn(III), Cr(III), Fe(III), Co(III), Zn(II) and Cd(II) have been prepared and characterised by elemental analysis, molar conductance values, magnetic susceptibility measurements and various spectral studies. The chemical studies and spectral data indicate that HATP and HBTP are in the hydrazone form. All complexes are six coordinates with O-h or D-4h symmetry. Fe(III), Mn(III) and Cr(III) complexes are of high spin while Co(III), Zn(II) and Cd(II) chelates are diamagnetic. Molecular mechanics calculations also confirm the complexation behaviour of the ligands. HATP is neutral tetradentate towards Zn(II), and Cd(II) whereas tridentate with Co(III) and Mn(III) havipg compositions [M(HATP)X-2] and [M-1(HATP)X-3] for M=Zn(II) and Cd(II) and M-1=Mn(III) and Co(III) and X=Cl, OAc and NO3. HBTP is neutral tridentate towards all the metals with composition [M(HBTP)(H2O)X-2] and [M-1(HBTP)X-3] where M=Cd(II) and Zn(II), M-1=Fe(III) and Cr(III) and X=Cl, OAc and NO3. Ligands and complexes have been screened for their antibacterial activity against gram-positive and gram-negative bacteria.