Mustayeen A. Khan

Synthesis, structural and spectral studies of 5-methyl 2-furaldehyde thiosemicarbazone and its Co, Ni, Cu and Cd complexes

Abstract The reaction of cobalt, nickel, copper and cadmium chlorides and bromides with 5-methylfurfural thiosemicarbazone (M5FTSC) leads to the formation of two series of new complexes: [M(M5FTSC)2X2], [M(M5FTSC)X2]. They have been characterized by spectroscopic studies (infrared, 1H NMR, and electronic spectra). The crystal structures of the free ligand M5FTSC and of the compound [CuCl2(M5FTSC)] have been determined by X-ray diffraction methods. For the Co(II), Ni(II) and Cu(II) complexes, the central atom is coordinated through the sulphur atom and the azomethine nitrogen atom whilst for the Cd(II) complexes, the coordination atoms are the sulphur and furanic oxygen atoms instead of the azomethine nitrogen.

Synthesis, structure and biological activity of nickel(II) complexes of 5-methyl 2-furfural thiosemicarbazone.

5-Methyl 2-furfuraldehyde thiosemicarbazone (M5HFTSC) with nickel(II) leads to three types of complexes: [Ni(M5HFTSC)(2)X(2)], [Ni(M5FTSC)(2)] and [Ni(M5FTSC)(2)] x 2DMF. In the first type the ligand remains in thione form, while in the two other, the anionic thiolato form is involved. The species [Ni(M5HFTSC)(2)X(2)] has been characterized spectroscopically. The structures of [Ni(M5FTSC)(2)] x 2DMF and [Ni(M5FTSC)(2)] have been solved using X-ray diffraction. Biological studies of [Ni(M5HFTSC)(2)Cl(2)] have been carried out in vitro for antifungal activity on human pathogenic fungi, Aspergillus fumigatus and Candida albicans, and in vivo for toxicity on mice. The results are compared to those of the ligand, the metal salt and a similar copper complex [Cu(M5HFTSC)Cl(2)].

Synthesis, crystal structure, characterization of zinc(II), cadmium(II) complexes with 3-thiophene aldehyde thiosemicarbazone (3TTSCH). Biological activities of 3TTSCH and its complexes

The reaction of zinc(II) chloride, cadmium(II) chloride and bromide with 3-thiophene aldehyde thiosemicarbazone leads to the formation of a series of new complexes. They have been characterized by spectroscopic studies: infrared, (1)H NMR, and electronic spectra. The crystal structures of the compound [ZnCl(2)(3TTSCH)(2)] and [CdBr(2)(3TTSCH)(2)] have been determined by X-ray diffraction methods. For the complexes [ZnCl(2)(3TTSCH)(2)] and [CdBr(2)(3TTSCH)(2)], the central ion is coordinated through the sulfur, and for the complexes [CdCl(2)(3TTSCH)], [CdBr(2)(3TTSCH)] the ion is coordinated through the sulfur as well as azomethine nitrogen atom of the thiosemicarbazone. In addition, fungistatic and bacteriostatic activities of both ligand and complexes have been evaluated. Cadmium(II) complexes have shown the most significant activities.

Geology of Petroleum in Kohat-Potwar Depression, Pakistan

The 36,000-km2 Kohat-Potwar depression in northern Pakistan has more than 5,000 m of marine deposition (Precambrian to Eocene, with a major break during Ordovician to Carboniferous). More than 10,000 m of Miocene to Pleistocene alluvial sediments overlies the marine sequence. The tectonic depression formed as a result of continent-to-continent collision at the northwestern margin of the Indian plate. Although the region has been under active petroleum exploration since the mid-nineteenth century, it has been tested by only 60 exploratory wells. Ten oil fields have been discovered; original recoverable reserves total 200 million bbl, of which 112 million bbl has been produced. The region has several attractive features for petroleum generation and accumulation i cluding source-reservoir-trap assemblages and thermal maturity regimes. Total ultimately recoverable hydrocarbon resource of the area is estimated at 2.4 billion bbl of oil equivalent. Many unexplored surface and subsurface prospects and stratigraphic leads are known. Parts of the region, particularly the Bannu depression and Kohat salt zone, can be regarded as frontier areas; based on the exposed geology and available seismic information, we believe these areas are promising. Recent discoveries of Dakhni field (1983) and Dhurnal field (1984), which were the first discoveries in the northern part of the platform zone of the Potwar plateau, and production from Paleozoic horizons have added new dimension to petroleum prospects of the area. The region needs careful reevaluation of available information, exploratory drilling on selected targets, and detailed exploration in its western part.

Metallic complexes from 2-furaldehyde semicarbazone and 5-methyl-(2-furaldehyde) semicarbazone

The synthesis and characterization of CoII, NiII, CuII and CdII complexes with 2-furfuralsemicarbazone (FSC) and 5-methyl 2-furfuralsemicarbazone (MFSC) are reported. These ligands lead to the complexes: [ML2X2] or [MLX2] (L = FSC or MFSC) whose structures were determined using elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra as well as by n.m.r. FSC and MFSC act as bidentate ligands in most of the CoII, NiII, CuII and CdII complexes. MFSC is a monodentate ligand in [NiBr2(MFSC)4].

Cytotoxicity of Metallic Complexes of Furan Oximes in Murine and Human Tissue Cultured Cell Lines

The copper complexes of 2-furaldehyde and furan oximes have previously demonstrated potent cytotoxicity, L1210 DNA synthesis inhibition, DNA topoisomerase II inhibition and DNA fragmentation. Currently a series of cobalt metal complexes of 2-furaldehyde oximes were compared with copper complexes of furan oximes to determine whether the type of metal is important to the cytotoxicity and mode of action of the complexes. The cobalt complexes of furan oximes, like the copper complexes, were shown to be cytotoxic to suspended tumor cell lines, e.g. leukemias, lymphomas, acute monocytic leukemia and HeLa-S3 uterine carcinoma. The cobalt complexes did not demonstrate dramatic cytotoxicity against the growth of tumors derived from solid human tumor lines. The cobalt complexes preferentially inhibited L1210 DNA synthesis, followed by inhibition of RNA and protein synthesis from 25 to 100 µM over 60 min. These agents, like the copper complexes of 2-furaldehyde and furan oximes, were inhibitors of DNA polymerase α activity and de novo purine synthesis with marginal inhibition of ribonucleoside reductase and dihydrofolate reductase activities with DNA fragmentation. Unlike the copper complexes, the cobalt complexes did not inhibit L1210 DNA topoisomerase II activity but did reduce thymidylate synthetase activity. Thus, varying the type of metal within the complexes of 2-furaldehyde and furan oximes produces differences in both cytotoxicity and mode of action. Copyright

Structural and spectral studies of thiosemicarbazones derived from 3-furaldehyde and 3-(2-furyl)prop-2-enal

Abstract 3-Furaldehyde thiosemicarbazone (3FTSC) and 3-(2-furyl)prop-2-enal thiosemicarbazone (FATSC) have been prepared, their structures solved and IR, 1 H NMR spectra recorded. The thiosemicarbazone moiety in both compounds shows an E configuration about C1–N2 and C2–N3. Intramolecular and intermolecular hydrogen bondings occur in both the molecules. The angles between the mean planes of the furanic ring and thiosemicarbazone moiety present a significant difference in the two compounds. Moreover, the 1 H NMR and IR spectral studies of two compounds are quite similar.

Formation of cobalt(II), nickel(II) and copper(II) chloro complexes in alcohols and the Irving-Williams order of stabilities

SummaryCoII chloro complexes were studied in MeOH at 25 °C and at constant ionic strength of 1 mol dm−3. Formation of three complexes is postulated for which the overall stability constants are calculated: logβ1 = 1.2, log β2 = 1.7 and log β3= 1.4. The electronic spectra and the formation curves of the identified species are presented for the first time in this medium. The results are compared with those obtained in other alcohols and increasing stability with increasing molecular weight of the solvents is established. Further comparative study showed that the maximum stability of the chloro complexes is found with the CuII ion as the central atom. This confirms the Irving-Williams order of stabilities for the first transition metal complexes in this alcoholic medium and the result is explained in terms of the second ionization potential of the elements.

Dioxygen activation with a cytochrome P450 model. Characterization and electrochemical study of new unsymmetrical tetradentate Schiff-base complexes with iron(III) and cobalt(II)

Salicylaldehyde or 5-bromosalicylaldehyde react with 2,3-diaminophenol to give two unsymmetrical Schiff-bases H2L1, H2L2, respectively. With Fe(III) and Co(II), these ligands lead to four complexes: Fe(III)ClL1, Fe(III)ClL2, Co(II)L1, Co(II)L2. The structures of these complexes were determined by mass spectroscopy, infrared and electronic spectra. Cyclic voltammetry in dimethylformamide (DMF) showed irreversible waves for both ligands. In the same experimental conditions, Fe(III)ClL1 exhibited a reversible redox couple Fe(III)/Fe(II) while the three other complexes showed quasi-reversible systems. The behavior of some of these complexes in the presence of dioxygen and the comparison with cytochrome P450 are described.

Stability constants of potent cytotoxic copper(II) complexes with furan semicarbazones in ethanolic solutions.

Potent cytotoxic copper(II) complexes of furannic semicarbazones were studied in ethanolic solutions at 25 degrees C. The four ligands used were synthesized in our laboratory, i.e. 2-furfural semicarbazone (FSC), 5-methyl 2-furfural semicarbazone (MFSC), 2-furfural 4-phenyl semicarbazone (FPSC) and 3-(2-furyl) prop-2-enal semicarbazone (FASC). The mathematical analysis was carried out with a recent computer program SIRKO which indicated the formation of one metal-ligand complex in each case and the logarithm of their stability constants are: log beta=2.02, 3.84, 4.58 and 4.52 for ligands FSC, MFSC, FASC and FPSC, respectively. A relation between stability and molecular weight of the ligands is proposed which may prove to be interesting as these complexes are being investigated for their cytotoxic activities.