Madan Mohan

Synthesis, characterization and antitumour properties of some metal(II) complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone and related compounds

Abstract Metal complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone (PCPH) and related compounds with manganese(II), iron(II), cobalt(II), nickel(Il), copper(II), zinc(II) and platinum(II) were synthesized and characterized by magnetic susceptibility measurements down to liquid nitrogen temperature and also by electronic, infrared, electron spin resonance and Mossbauer spectra. All the metal(II) complexes appeared to be monomeric, high-spin, five-coordinate (square-pyramidal) (X = Cl − or OAc − ), except for Ni(PCPH)Cl 2 which is polymeric, high-spin, six-coordinate. Each ligand behaved as a tridentate NNN donor, via the pyridine nitrogen, azomethine nitrogen, and pyridine or quinoline nitrogen. One of the most active agents of this series, Cu(PCPH)Cl 2 , showed antitumour activity against a variety of transplanted tumours, including Sarcoma 180, Ehrlich carcinoma and L1210 leukaemia sensitive to α( N )-heterocyclic carboxaldehyde thiosemicarbazones. This agent caused inhibition of 3 H-thymidine and 3 H-uridine incorporation into DNA and RNA, respectively, of Sarcoma 180 ascites cells; protein biosynthesis was relatively insensitive to the action of this agent.

Metal Complexes of 2,6-Diacetylpyridine Bis(thiosemicarbazone): their Preparation, Characterization and Antitumour Activity

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 2.6-diacetylpyridine bis(thiosemicarbazone) (daptsc-H2) have been isolated and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature to liquid nitrogen temperature), diffuse reflectance and infrared studies. On the basis of these studies a seven-coordinate structure for Zn(daptsc-H2)(OAc)2, a six-coordinate structure for M(daptsc-H2)Cl2 (MMn(II), Co(Il), Ni(II) or Cu(II)) and Fe(daptsc-H2)SO4, and a five-coordinate structure for Pt(daptsc) are suggested. 57Fe Mossbauer spectra at 300 and 78 K also suggest a distorted octahedral structure with dxy ground state for Fe(daptsc-H2)SO4 complex. All these metal(II) complexes have been screened for their antitumour activity in the P388 lymphocytic leukaemia test system in mice and showed enhanced antitumour activity relative to the free ligand.

Synthesis, characterization and antitumor activity of manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and platinum(II) complexes of 3- and 5-substituted salicylaldehyde benzoylhydrazones

Abstract Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde benzoylhydrazones (XSBH, X = H, 3-NO 2 , 3-CH 3 O, 5-Br, 5-Cl, 5-CH 3 or 5-NO 2 ) were prepared and characterized by elemental analyses, conductance measurements, magnetic moments (300−78 K) and spectral studies. On the basis of these studies the following structures are suggested: distorted octahedral for Mn(XSBH) 2 , dimeric, low-spin, five- coordinate for Ni(XSBH)Cl·2H 2 O, dimeric, high-spin, five-coordinate for Co(XSBH)Cl·2H 2 O, dimeric four- coordinate for Zn(XSBH) and a square-planar structure for M(XSBH)Cl·H 2 O (M = Cu(II) or Pt(II)). The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d x 2− y 2 ground state in square-planar stereochemistry. All the metal(II) complexes were screened for their antitumor activity against the P388 lymphocytic leukaemia test system in mice and were found to possess no significant activity at the dosages used.

Synthesis, characterization and antitumour activity of iron(II) and iron(IlI) complexes of 3- and 5-substituted salicylaldehyde benzoyl hydrazones

Abstract Iron(II) and iron(III) complexes of tridentate ligands derived from various substituted salicylaldehydes and benzoyl hydrazones have been prepared and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature down to liquid N2 temperature), and Mossbauer, electronic and infrared spectral studies. On the basis of these studies the following structures are suggested: monomeric, high-spin, five-coordinate for Fe(XSBH)SO4·H2O (XSBH = substituted salicylaldehyde benzoyl hydrazone, X = H, 3-CH3O, 3-NO2, 5-Cl, 5-Br, 5-CH3 or 5-NO2); dimeric, high-spin, phenoxide bridged, five-coordinate for Fe(H-SBH)Cl (H-SBH = salicylaldehyde benzoyl hydrazone); and monomeric, high-spin, six-coordinate for Fe(XSBH) Cl2·H2O (X = 3-CH3O, 3-NO2, 5-Cl, 5-Br, 5-CH3 or 5-NO2). Intermolecular antiferromagnetic exchange interaction is present in the dimeric Fe(XSBH)Cl complex, where the exchange parameter is −7.3 cm−1. The complex exhibits an asymmetrical quadrupole-split doublet in its 57Fe Mossbauer spectra. The asymmetry is found to be temperature dependent with a relatively symmetrical doublet at low temperature. All these complexes have been screened for their antitumour activity against the P388 lymphocytic leukaemia test system in mice and have been found to possess no significant activity at the dosages employed.

Synthesis, characterization and antitumor activity of some metal complexes of 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones

Abstract Complexes of Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde o -hydroxybenzoylhydrazones (XSBH, X = H, 3-NO 2 , 3-CH 3 O, 5-Cl, 5-Br, 5-CH 3 or 5-NO 2 ) have been prepared and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature down to liquid nitrogen temperature) and spectral studies. These studies indicate the following structures: monomeric, high-spin, distorted octahedral for Mn(XSBH) 2 ; monomeric, high-spin, five-coordinate for Fe(XSBH)SO 4 ·H 2 O; dimeric, high-spin phenoxide bridged, five-coordinate for Fe(XSBH)Cl; dimeric, high-spin five-coordinate for Co(XSBH)Cl·2H 2 O; dimeric low-spin, five-coordinate for Ni(XSBH)Cl·2H 2 O; dimeric, four-coordinate for Zn(XSBH); and a square-planar structure for M(XSBH)Cl·H 2 O (M = Cu(II) or Pt(II). Intermolecular antiferromagnetic exchange interactions are present in Fe(III) complexes, where the exchange parameter ( J ) is ca . −8.0 cm −1 for these complexes. The Fe(III) complexes exhibit asymmetric quadrupole split doublets in their 57 Fe Mossbauer spectra. The asymmetry is found to be temperature dependent with relatively symmetrical doublets seen at low temperature. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d x 2 −y 2 ground state in square-planar stereo-chemistry. All these metal complexes have been screened for their antitumor activity against the P 388 lymphocytic leukaemia test system in mice and enhanced antitumor activity relative to the free ligand was found but no significant activity at the dosages used.

Magnetic and mössbauer characterization of the discontinuous high-spin (6A1)⇄low-spin (2T2) transition in solid bis(pyridoxal 4-phenylthiosemicarbazonato)iron(III) chloride

Abstract The iron(III) complexes [Fe(HPhthsa) 2 ]Cl, [Fe(HEtthsa) 2 ]Cl and [Fe(HMethsa) 2 ]Cl were synthesized and the phenomenon of discontinuous spin transition between the high-spin ( 6 A 1 , S =5/2) and the low-spin ( 2 T 2 , S =1/2) states in [Fe(HPhthsa) 2 ]Cl was confirmed by the measurement of temperature dependent magnetism and Mossbauer spectra. The tridendate ligands used were pyridoxal 4-phenylthiosemicarbazone (H 2 Phthsa), pyridoxal 4-ethylthiosemicarbazone (H 2 Etthsa), and pyridoxal 4-methylthiosemicarbazone (H 2 Methsa). The magnetic moments for the spin-crossover complex show a thermal hysteresis of width δ T ≈9 K with the transition centered at T c ↑ ≈299 K for increasing temperature and at T c ↓ ≈290 K for decreasing temperature. Variable temperature 57 Fe Mossbauer results also provide evidence for the presence of a first order phase transition in this complex. The first order (cooperative) nature of the spin-crossover transformation most likely occurs through the extended coupling of ferric complexes via intermolecular H bonds. The EPR results indicate that the ground state is a well separated Kramers doublet in the low-spin complexes.

Transition metal chemistry of oxime — Containing ligands, Part XXVIII; manganese(II) complexes of 2,6-diacetylpyridine dioxime

SummaryComplexes of manganese(II) with the tridentate oxime ligand 2,6-diacetylpyridine dioxime (H2dapd) have been synthesized and characterized. The complexes [Mn(H2dapd)X2] are pentacoordinate for X = Cl, Br or I but apparently octahedralvia bridging anions for X = NCS or NCSe. The complex [Mn(H2dapd)(NO3)2] adopts an octahedral structure involving monodentate and bidentate coordination of nitro groups. The complexes [Mn(H2dapd)2]X2 (X = Cl, Br, I, NO3, NCS or NCSe) involve an octahedral cation.

Vanadium metabolism in tunicates: The coordination chemistry of V(III), V(IV), and V(V) with models for the tunichromes

Abstract Two isomeric tunichrome model compounds have been prepared from spermidine and trihydroxybenzoic acid. The coordination chemistry of these ligands with V(III), (IV), and (V) are reported. Vanadium(V) is found to undergo rapid reduction to V(IV) in the presence of these ligands, Vanadium(IV) complexes were characterized by optical and EPR spectroscopy as well as elemental analysis and magnetic measurements. Vanadium(III) also reacts rapidly with these ligands, producing what is thought to be a VOV dimer in acidic solution. The biological implications of the coordination chemistry reported herein with respect to vanadium metabolism in ascidians is discussed.

Synthesis, characterization and antitumor properties of some metal complexes of 30and 5-substituted salicylaldehyde 2-pyridinylhydrazones

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Pt(II) with 3- and 5-substituted salicylaldehyde 2-pyridinylhydrazones (XSPH, X = H, 3-NO2, 3-CH3O, 5-Br, 5-Cl, 5-CH3, or 5-NO2) have been prepared and characterized by elemental analysis, conductance measurements, magnetic moments (300-78 K), and spectral studies. On the basis of these studies a monomeric, high-spin, distorted octahedral structure for Mn(XSPH)2 and Fe(XSPH)2, a dimeric, high-spin, five-coordinate structure for Co(XSBH)Cl, a dimeric, low-spin, five-coordinate structure for Ni(XSPH)Cl and Zn(XSPH)(OAc), and a square-planar structure for M(XSPH)Cl.H2O (M = Cu(II) or Pt(II] complexes are suggested. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and suggest dx2-y2 ground state in square-planar stereochemistry. Mössbauer spectral results indicate distorted octahedral structure for iron(II) complexes. All the metal(II) complexes have been screened for their antitumor activity against P388 lymphocytic leukemia test system in mice and have been found to possess no significant activity at the dosages used.

Synthesis, magnetic and electrochemical properties of binuclear copper(II) complexes of pyridoxal hydrazones

Abstract Some new binuclear copper(II) complexes with pyridoxal benzoylhydrazone (PBH), pyridoxal o-hydroxylbenzoyl- hydrazone (PHBH), pyridoxal picolinoylhydrazone (PPH), pyridoxal nicotinoylhydrazone (PNH), and pyridoxal isonicotinoylhydrazone (PINH) have been synthesized and characterized by analytical, magnetic, spectral, ESR and electrochemical methods. All the complexes exhibit normal magnetic moments at room temperature. The variable temperature magnetic moments, however, indicate the presence of very weak intramolecular antiferro- magnetic interactions (−2J ≈~90 cm−1) in between the copper(II) centers in the complexes. The ESR spectral data at 77 K are characteristic of binuclear CuCu complexes and exhibit a seven-line pattern in the low field gl region. The cyclic voltammograms of each complex showed two oxidation waves attributed to Cu2II,II→Cu2II,III and Cu2II,III→Cu2III,III processes at significantly low potentials.