Tahir Ali Khan

Synthesis and Characterization of bis(Macrocyclic) Complexes Based on the 13-Membered Pentaaza Unit

Abstract The template condensation of triethylenetetraamine, formaldehyde and benzidine in 2:4:1 molar ratio results in new types of binuclear bis(macrocyclic) complexes, [M2LX4] [M = Mn, Co, Ni, Cu, Zn, X = Cl or NO3] in which two pentaazacyclotetradecane subunits are linked by a biphenyl group attached to an uncoordinated benzidine nitrogen atom. The complexes synthesized were characterized by IR, 1H NMR, UV/VIS, EPR, conductivity, magnetic moments and analytical data. The observed low conductance values of all these complexes suggests their non-ionic character and that all the complexes exhibit octahedral geometry around the metal ions. Referee I: E. Rosenberg Referee II: K. Moedritzer

Synthesis and characterization of Schiff base octaazamacrocyclic complexes and their biological studies

A condensation reaction between 1,2-diphenylethane-1,2-dione dihydrazone (DPEDDH) and dimethyl or diethyloxalate in methanol resulted in a novel Schiff base octaazamacrocyclic ligand, (L): (6,7,14,15-tetraoxa-2,3,10,11-tetraphenyl-1,4,5,8,9,12,13,16-octaazacyclohexadecane-1,3,9,11-tetraene). Subsequently metal complexes of the type [MLX2] and [CuL]X2; (M=Mn(II), Co(II), Ni(II) and Zn(II); X=Cl or NO3) were synthesized by the reaction of the free macrocyclic ligand (L) with the corresponding metal salts in 1:1 molar ratio. These complexes were characterized on the basis of analytical data, molar conductivity and magnetic susceptibility measurements, ESI-mass, IR, NMR ((1)H and (13)C), EPR and electronic spectral studies. The thermal stability of the complexes was also studied by TGA and DTA analyses. These studies show that all the complexes have octahedral arrangement around the metal ions except copper complexes which are square planar. The ligand and its complexes were screened for their antibacterial activity in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and were also studied for their anticancer activity against the human cancer cells lines: HeLa (Human cervical carcinoma), MCF7 (Human breast adenocarcinoma) and Hep3B (Human Hepatocellular carcinoma). The recorded IC50 values for the tested compounds show moderate to good cytotoxicity against these cancer cell lines. The copper complex, [CuL]Cl2, showed excellent antimicrobial activity against tested microorganisms which is almost equivalent to the standard drug ciprofloxacin.

Tetraoxotetraamide macrocyclic complexes

A new class of 16- and 17-membered tetraamide macrocyclic complexes, [ML1X2] and [ML2X2] [M = MnII, CoII, NiII, CuII or ZnII; X = NO3 or Cl], have been prepared by the template reaction of anthranilic acid, 1,2-diaminoethane or 1,3-diaminopropane and succinic acid in 2:1:1 molar ratio. The stoichiometries and coordination modes of the complexes have been deduced from physicochemical and spectroscopic measurements.

Interaction of Co(II), Ni(II), Cu(II), and Zn(II) with 12- and 14-membered macrocycles containing O2N2 donors

The 12- and 14-membered diazadioxo macrocyclic ligands, 1,2 : 7,8-diphenyl-6,9-diaza-3,12-dioxocyclododecane (L1) and 1,2 : 8,9-diphenyl-7,10-diaza-3,14-dioxocyclotetradecane (L2), were synthesized by condensation between o-phenylenediamine, 1,2-dibromoethane/1,3-dibromopropane, and catechol. Metal complexes [ML1Cl2] and [ML2Cl2] [M = Co(II), Ni(II), Cu(II), and Zn(II)] were prepared by interaction of L1 or L2 with metal(II) chlorides. The ligands and their complexes were characterized by elemental analyses, IR, 1H, and 13C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements, and Electrospray ionization-mass spectral (ESI-MS) studies. The results of elemental analyses, ESI-MS, Jobs method, and conductivity measurements confirmed the stoichiometry of ligands and their complexes while absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand framework around the metal ions. Stereochemistry was inferred from the UV-Vis, EPR, and magnetic moment studies.

Coordinating Properties of Chlorosulphate Ion; Synthesis and Characterization of Mn (II), Co (II), Ni(II) and Cu(II) Bis-(Chlorosulphates) and Their Complexes with Nitrogen-Containing Bases

Abstract Chlorosulphates of the divalent transition metals Mn(II), Co(II), Ni(II) and CU(II) have been prepared and characterized. The electrical conductivities and i.r. spectral data indicate a considerable extent of cation-anion interaction and the anion is bonded in a tridentate manner such that it has a reduced Cs symmetry in the molecule. The magnetic susceptibility measurements and the ligand field spectroscopic studies are consistent with the octahedral geometry for these salts and indicate the presence of some covalent bonding between the chlorosulphate ion and the metal ion. However, a tetragonal distortion in the geometry has been indicated for the Ni(II) salt. The coordination compounds of the type ML4(SO3Cl)2[L=acetonitrile, pyridine, pyridine N-oxide] and ML2(SO3Cl)2 [L = 2,2′bipyridine, acridine] have also been prepared and characterized. The i.r. and ligand field spectroscopic studies and magnetic susceptibility measurements indicate the presence of a strong interaction between the anion an...

Complexes of Group (IV) Metal Halides with Pyrazolones

Abstract The preparation and characterization of Ge(IV), Sn(IV), Ti(IV) and Zr(IV) halide complexes of antipyrine and 4-amino-antipyrine have been described. The low frequency IR spectra indicate a trans-octahedral geometry involving unidentate or bidentate ligands, however, a cis-octahedral structure is proposed for the GeCl4 complex of 4-aminoantipyrine. A polymeric structure is proposed for the 1:1 complexes of 4-aminoantipyrine involving ligand bridging through the carbonyl oxygen and the amino nitrogen.

Template synthesis and spectroscopic studies of highly conjugated tetraiminetetraamide macrocyclic complexes from 1,2-diphenylethane-1,2-dione dihydrazone

A new class of tetraiminetetraamide macrocyclic (Ph4[20]tetraene, N8O4, and Ph6[20]tetraene, N8O4) complexes have been prepared through the metal ion controlled reaction of 1,2-diphenylethane-1,2-dione dihydrazone (DPEDDH) with succinic acid [ML1X2] or phthalic acid [ML2X2] [M=Mn, Co, Ni, Cu or Zn; X=Cl or NO3]. The structures of the complexes have been elucidated on the basis of i.r, 1H-n.m.r, e.p.r. and electronic spectral data and conductance, as well as magnetic, properties. An octahedral geometry is assigned for all the complexes, involving coordination of the all-imine nitrogens.

Synthesis and Physico‐Chemical Studies on 18‐Membered Octaazamacrocyclic Complexes of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) Ions

Abstract A new series of 18‐membered octaazamacrocyclic complexes [ML1X2] and [ML2X2] (M = Mn(II), Co(II), Ni(II), Cu(II), and Zn(II); X = Cl or NO3) have been synthesized by template condensation of o‐phthalaldehyde with hydrazine hydrate and formaldehyde or acetaldehyde in MeOH. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, FT‐IR, 1H NMR, EPR, UV spectroscopy, magnetic susceptibility, and conductivity measurements. An octahedral geometry has been suggested for all the complexes and the observed low molar conductance values indicate their non‐ionic nature.

Metal Ion Directed Synthesis of 12 and 14-Membered Tetraaza Macrocyclic Complexes and their Physico-Chemical Studies

The template condensation reaction of o-phenylenediamine with 2,3-butanedione or 2,4-pentanedione resulted in the formation of new series of 12 and 14-membered tetraaza macrocyclic complexes: [ML1Cl2], [ML2Cl2] [M=Co(II), Ni(II) and Zn(II)]; [CuL1]Cl2 and [CuL2]Cl2. The formation of the macrocyclic framework and the overall geometry of the complexes have been characterized by elemental analyses, FT-IR, 1HNMR, UV-Visible, magnetic susceptibility and conductivity measurements. The copper(II) complexes exhibit square planar geometry, whereas an octahedral geometry is suggested for all other complexes.

TRANSITION METAL ION DIRECTED BIMETALLIC MACROCYCLIC COMPLEXES

Template condensation of 1,4-phenylenediamine, formaldehyde, 1,3-diaminopropane and benzil in a 1:4:4:2, molar ratio results in the formation of a new series of binuclear decaazamacrocyclic complexes: dichloro/nitrato [1-phenyl bis(8,9-diphenyl-1,3,7,10,14 pentaazacyclo-pentadeca-7,9-diene) metal (II)], [M2LX4](M = MnII, CoII, NiII, CuII and ZnII, X = Cl or NO3), which were characterised by i.r., 1H-n.m.r., e.p.r., u.v–vis. spectral studies, conductivity and magnetic susceptibility measurements. All the complexes show octahedral geometry.