Mohammad Akbar Ali

Biological activity of palladium(II) and platinum(II) complexes of the acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate and the X-ray crystal structure of the [Pd(asme)2] (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) complex.

Palladium(II) and platinum(II) complexes of general empirical formula, [M(NS)(2)] (NS=uninegatively charged acetone Schiff bases of S-methyl- and S-benzyldithiocarbazate; M=Pt(II) and Pd(II)) have been prepared and characterized by a variety of physicochemical techniques. Based on conductance, IR and electronic spectral evidence, a square-planar structure is assigned to these complexes. The crystal and molecular structure of the [Pd(asme)(2)] complex (asme=anionic form of the acetone Schiff base of S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted cis-square planar structure with the ligands coordinated to the palladium(II) ions as uninegatively charged bidentate NS chelating agents via the azomethine nitrogen and the mercaptide sulfur atoms. The distortion from a regular square-planar geometry is attributed to the restricted bite angles of the ligands. Antimicrobial tests indicate that the Schiff bases exhibit strong activities against the pathogenic bacteria, Bacillus subtilis (mutant defective DNA repair), methicillin-resistant Staphylococcus aureus, B. subtilis (wild type) and Pseudomonas aeruginosa and the fungi, Candida albicans (CA), Candida lypotica (2075), Saccharomyces cerevisiae (20341) and Aspergillus ochraceous (398)-the activities exhibited by these compounds being greater than that of the standard antibacterial and antifungal drugs, streptomycin and nystatin, respectively. The palladium(II) and platinum(II) complexes are inactive against most of these organisms but, the microbe, Pseudomonas aeruginosa shows strong sensitivity to the platinum(II) complexes. Screening of the compounds for their cytotoxicities against T-lymphoblastic leukemia cancer cells has shown that the acetone Schiff base of S-methyldithiocarbazate (Hasme) exhibits a very weak activity, whereas the S-benzyl derivative (Hasbz) is inactive. However, the palladium(II) complexes exhibit strong cytotoxicities against this cancer; their activities being more than that of the standard anticancer drug, tamoxifen. The [Pt(asme)(2)] complex exhibits a very weak cytotoxicity, whereas [Pt(asbz)(2)] is inactive against leukemic cells.

The synthesis, characterization and bioactivities of some copper(II) complexes of the 2-acetylpyridine schiff bases of s-methyl- and s-benzyldithiocarbazate, and the x-ray crystal structure of the nitrato(s-benzyl-β-n-(2-acetylpyridyl) methylenedithiocarbazato)copper(II) complex

Copper(II) complexes of the general formula [Cu(Ap-SMe)X] or [Cu(Ap-SBz)X] (where HAp-SMe and HAp-SBz, respectively, represent the 2-acetylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; XCl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for the [Cu(Ap-SMe)X] (XCl, Br) complexes and a five-coordinate structure for the [Cu(Ap-SBz)NO3] complex. The structure of [Cu(Ap-SBz)NO3] has been determined by X-ray diffraction studies. The geometry of the complex is a distorted square-pyramid with the NNS tridentate ligand and an oxygen atom of the nitrate ion occupying the basal plane. The fifth coordination position is occupied by another oxygen from the nitrate ion. The anti-fungal and anti-bacterial properties of the Schiff bases and their copper(II) complexes have been evaluated against the phytopathogenic fungi A. solanyi, F. equisetti and M. phaseolina and the pathogenic bacteria E. coli and S. aureas. The fungitoxicity of the five-coordinated [Cu(Ap-SBz)NO3] complex approaches that of nystatin, whereas the Schiff base HAp-SMe and its copper(II) complex [Cu(Ap-SMe)NO3] display significant antibacterial activity against E. coli and S. auereas.

The preparation and characterization of bis-chelated nickel(II) complexes of the 6-methylpyridine-2-carboxaldehyde Schiff bases of S-alkyldithiocarbazates and the X-ray crystal structure of the bis {S-methyl-β-N- (6-methylpyrid-2-yl)- methylenedithiocarbazato}nickel(II) complex

Abstract New nickel(II) complexes of general formula, [Ni(NNS)2] (NNS− = uninegatively charged tridentate ligands formed by condensation of 6-methyl-2-formylpyridine with S-methyl- and S-benzyldithiocarbazates) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a distorted octahedral structure for these complexes. The crystal and molecular structure of the bis{S-methyl-β-N-(6-methylpyrid-2-yl)methylenedithiocarbazato}nickel(II) complex has been determined by X-ray diffraction studies. The complex has a distorted octahedral structure with the ligands coordinated to the nickel(II) ion as uninegatively charged tridentate chelating agents via the pyridine nitrogen, the azomethine nitrogen and the mercaptide sulphur atoms. The distortion from the regular octahedral geometry is ascribed to the stereochemical limitations imposed by the planar tridentate ligands.

The preparation and characterization of some copper(II) Complexes of the 6-methyl-2-formylpyridine thiosemicarbazone and the x-ray crystal structure of the chloro(6-methyl-2-formylpyridinethiosemicabazonato) copper(II) complex

Abstract Copper(II) complexes of general empirical formulae, [Cu(NNS)X] · xH 2 O (NNS = uninegatively charged tridentate ligand formed by condensation of 6-methylpyridine-2-aldehyde with thiosemicarbazide ; X = Cl, Br, NO 3 , and CH 3 COO; x= 0, 1) and [Cu(NNS) 2 ] · 0.5H 2 O have been prepared and characterized by conductance, magnetic, electronic and infrared spectroscopic measurements. Magnetic and spectral data support a square-planar structure for [Cu(NNS)X] (X = Cl, Br, NO 3 , CH 3 COO) and a distorted octahedral structure for [Cu(NNS) 2 ] · 0.5H 2 O. The crystal and molecular structure of [Cu(NSS)Cl] has been determined by X-ray diffraction. This complex has a distorted square-planar geometry with the copper(II) ion lying in an approximate plane of four coordinating atoms, three of which come from the 6-methylpyridine-2-carboxaldehyde thiosemicarbazone and the fourth coordination site is occupied by the chloride ligand. The thiosemicarbazone is present as the thiolate form and is coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the mercaptide sulfur atom. Copyright

Synthesis and characterization of mono- and bis-ligand zinc(II) and cadmium(II) complexes of the di-2-pyridylketone Schiff base of S-benzyl dithiocarbazate (Hdpksbz) and the X-ray crystal structures of the [Zn(dpksbz)2] and[Cd(dpksbz)NCS]2 complexes

New mono- and bis-chelated zinc(II) and cadmium(II) complexes of formula, [M(dpksbz)NCS] (dpksbz = anionic form of the di-2-pyridylketone Schiff base of S-benzyldithiocarbazate) and [M(dpksbz)(2)] (M = Zn-II, Cd-II) have been prepared and characterized. The structure of the bis-ligand complex, [Zn(dpksbZ)(2)] has been determined by X-ray diffraction. The complex has a distorted octahedral geometry in which the ligands are coordinated to the zinc(II) ion as uninegatively charged tridentate chelates via the thiolate sulfur atoms, the azomethine nitrogen atoms and the pyridine nitrogen atoms. The distortion from a regular octahedral geometry is attributed to the restricted bite angles of the Schiff base ligands. X-ray structural analysis shows that the [Cd(dpksbz)NCS](2) complex is a centrosymmetric dimer in which each of the cadmium(II) ions adopts a five-coordinate, approximately square-pyramidal configuration with the Schiff base acting as a tetradentate chelating agent coordinating a cadmium(II) ion via one of the pyridine nitrogen atoms, the azomethine nitrogen atom and the thiolate sulfur atom; the second pyridine nitrogen atom is coordinated to the other cadmium(II) ion of the dimer. The fifth coordination position around each cadmium(II) is occupied by an N-bonded thiocyanate ligand

Synthesis and characterization of copper(II) complexes of the methylpyruvate Schiff base of S-methyldithiocarbazate (Hmpsme) and the X-crystal structures of Hmpsme and (Cu(mpsme)Cl)

Abstract New copper(II) complexes of general formula, [Cu(mpsme)X] (mpsme=anionic form of the methylpyruvate Schiff base of S-methyldithiocarbazate; X=Cl−, Br−) have been prepared and characterized by a variety of physico-chemical techniques. Based on magnetic and spectral evidence, a square-planar structure is assigned to these complexes. Reaction of the Schiff base with copper(II) nitrate does not yield a nitrato–copper(II) complex of the ligand. Instead, hydrolysis of the Schiff base occurs with the concomitant formation of the copper(II) complex of the pyruvic acid Schiff base of S-methyldithiocarbazate. Based on magnetic and spectral evidence, an oxygen-bridged square-planar structure is assigned to this complex. The crystal and molecular structures of the Schiff base, Hmpsme and its chlorocopper(II) complex, [Cu(mpsme)Cl] have been determined by X-ray diffraction. The [Cu(mpsme)Cl] complex has a distorted square-planar structure with the ligand coordinated to the copper(II) ion as a uninegatively charged tridentate chelating agent via the carbonylic oxygen atom, the azomethine nitrogen atom and the thiolato sulfur atom. The fourth coordination position around the copper(II) ion is occupied by the chloride ligand. The distortion from regular square-planar geometry is attributed to the restricted bite size of the ligand.

The preparation and characterization of mono- and bis-chelated cadmium(II) complexes of the di-2-pyridylketone Schiff base of S-methyldithiocarbazate (Hdpksme) and the X-ray crystal structure of the [Cd(dpksme)2] · 0.5 MeOH complex

New cadmium(II) complexes of empirical formulae, [Cd(dpksme)X] (dpksme = anionic form of the Schiff base; X = NCS−, Cl−, I−) and [Cd(dpksme)2] · 0.5MeOH, respectively have been prepared and characterized. The mono-ligated cadmium(II) complexes, [Cd(dpksme)X] are four-coordinate and tetrahedral but the bis-ligand complex, [Cd(dpksme)2] · 0.5MeOH is six-coordinate and octahedral. The crystal and molecular structure of [Cd(dpksme)2] · 0.5MeOH has been determined by X-ray diffraction. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The Schiff base and its cadmium(II) complexes exhibit mild antibacterial activities against Shigella dysenteriae, Bacillus cereus, Staphylococcus aureus and Escherichia coli. They are also mildly fungitoxic against the phytopathogenic fungi, Alternaria alternata and Macrophomina phaseolina.

Mono- and bis-chelated nickel(II) complexes of the di-2-pyridylketone Schiff base of S-methyldithiocarbazate and the X-ray crystal structure of the bis[S-methyl-β-N-(di-2-pyridyl)-methylenedithiocarbazato]nickel(II) complex

Abstract The di-2-pyridylketone Schiff base of S-methyldithiocarbazate (Hdpksme) reacts with nickel(II) salts giving both mono- and bis-chelated complexes of empirical formulae, [Ni(dpksme)X] (dpksme=anioninc form of the Schiff base; X=NCS−, Cl−) and [Ni(dpksme)2], respectively. These compounds have been characterized by magnetic and spectroscopic techniques. The mono-ligated nickel(II) complexes are four-coordinate and square-planar but the bis-ligand complex is six-coordinate and octahedral. The crystal and molecular structure of [Ni(dpksme)2] has been determined by X-ray crystallography. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The ligand and its nickel(II) complexes exhibit weak antimicrobial activity against the pathogenic bacteria, S. dysenteriae, B. cercus, S. aureus and E. coli and the fungi, A. alternata and M. phaseolina.

Synthesis and characterization of some four- and five-coordinate copper(II) complexes of 6-methyl-2-formylpyridinethiosemicarbazone (HNNS) and the X-ray crystal structures of the [Cu(NNS)(CH3COO)(H2O)] and [Cu (HNNS) (H20) (S04)) - H2O complexes

Abstract Copper(II) complexes of general formula, [Cu(NNS)(H2O)xX] · nH2O (NNS− = uninegatively charged tridentate thiosemicarbazone ligand formed from 6-methyl-2-formylpyridine; X = NCS−, CH3COO−, N3−; x = 0,1; n = 0.5, 1) and [Cu(HNNS)(H2O)(SO4)] · H20 have been synthesized and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for the [Cu(NNS)X] (X = NCS−, N3−) complexes and a five-coordinate structure for the [Cu(HNNS)(H2O)(SO4)] · H2O complex. The crystal structures of the [Cu(NNS)(CH3COO)(H2O)] and [Cu(HNNS)(H2O)(SO4)] · H2O complexes have been determined by X-ray diffraction. The acetato complex has a distorted square-pyramidal geometry with the thiosemicarbazone ligand acting as a uninegatively charged tridentate NNS chelating agent and the fourth and fifth coordination positions of the copper(II) ion are occupied by a unidentate acetate and water ligand, respectively. The sulphato-complex is also five-coordinate with the thiosemicarbazone coordinated as a neutral NNS ligand and the fourth and fifth coordination sites are occupied by a water molecule and a unidentate sulphate ligand, respectively.

Preparation, characterization and antifungal properties of nickel(II) complexes of tridentate ONS ligands derived from N-methyl-S-methyldithiocarbazate and the X-ray crystal structure of the [Ni(ONMeS)CN]·H2O complex

Nickel(II) complexes of general empirical formula, NiLX·nH2O (L = deprotonated form of the Schiff base formed by condensation of N-methyl-S-methyldithiocarbazate with 2-hydroxybenzaldehyde or 5-bromo-2-hydroxybenzaldehyde; X = Cl−, Br−, NCS−, AcO− or CN−; n = 0, 1) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectroscopic data support a square-planar structure for these complexes. The crystal structure of the [Ni(ONMeS)CN]·H2O complex (ONMeS = anionic form of the 2-hydroxybenzaldehyde Schiff base of N-methyl-S-methyldithiocarbazate) has been determined by X-ray diffraction. The complex has a distorted square-planar structure in which the Schiff base is coordinated to the nickel(II) ion as a uninegatively charged anion coordinating via the phenolic oxygen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth coordination position is occupied by a cayano ligand. The antifungal properties of the Schiff bases and their nickel(II) complexes were studied against three plant pathogenic fungi. The ligands display moderate fungitoxicities against these organisms but their nickel(II) complexes are less active than the free ligands.