M. T. H. Tarafder

S-methyldithiocarbazate and its Schiff bases: evaluation of bondings and biological properties.

Eight selective nitrogen-sulfur donor ligands have been synthesized from the condensation of S-methyldithiocarbazate (SMDTC) with aldehydes and ketones with a view to evaluating their antimicrobial and cytotoxic activities, and also to correlate the biological properties with the structure of the ligands. The compounds were all characterized by elemental analyses and other physicochemical techniques. SMDTC and the Schiff bases were screened for antimicrobial and cytotoxic activities. SMDTC showed very large inhibition zones (24-44 mm) against bacteria and fungi with a minimum inhibitory concentration (MIC) of 390-25,000 and 1562-6250 microg ml(-1), against different bacteria and fungi, respectively. Streptomycin and nystatin were used as the internal standards against bacteria and fungi, respectively. SMDTC along with its Schiff bases with pyridine-2-carboxaldehyde, acetylacetone and 2,3-butanedione were strongly antifungal and the MIC values were comparable to nystatin. Most of the Schiff bases were strongly cytotoxic. In particular, those with pyridine-2-carboxaldehyde and 2,3-butanedione have CD(50) values of 5.5, 1.9-2.0 microg ml(-1), respectively, against leukemic cells, while against colon cancer cells, the values were 3.7 and 2.0 microg ml(-1), respectively. The glyoxal Schiff base was strongly active only against leukemic cell with CD(50) value of 4.0 microg ml(-1). The present findings have been compared with standard drugs.

Synthesis and characterization of some new nickel(II), zinc(II) and cadmium(II) complexes of quadridentate SNNS ligands

Abstract Two new quadridentate Schiff base ligands formed from 2,5-hexanedione and S-alkyldithiocarbazic acids and their nickel(II), zinc(II) and cadmium(II) complexes having the general formula [M(SNNS)] (SNNS 2− is the dinegatively charged ligands) have been synthesized and characterized by elemental analysis and magnetic and spectroscopic methods. The Ni(SNNS) complexes are diamagnetic and square-planar. The Zn(SNNS) complexes are assigned with polymeric structures with mercapto sulphur-bridging. The Cd(SNNS) complexes presumably have polymeric structures.

Metal complexes of some schiff bases derived from s-benzyldithiocarbazate

Abstract New metal complexes of Schiff base ligands derived from S-benzyldithiocarbazate have been prepared and characterized by elemental analysis and magnetic and spectroscopic measurements. In neutral or slightly acidic media, the Schiff bases formed from acetone, benzophenone, acetaldehyde and benzaldehyde behave as neutral [NS] bidentate chelating agents forming both bis- and tris-chelated nickel (II) complexes of general formula, Ni[NS] 2 X 2 (X = Cl − , NCS − ) and Ni [NS] 3 X 2 (X = Cl − , Br − and NO 3 − ), respectively, which are high-spin and octahedral. The complexes, Co[NS] 3 X 2 (X = Cl − or NO 3 − ) and Cu[NS] 2 (NO 3 ) 2 were also isolated. Magnetic and spectral evidence support an octahedral structure for the cobalt(II) complexes and a square-planar structure for the copper(II) complexes. In the presence of alkali the NS Schiff bases deprotonate yielding neutral complexes, Ni[NS − ] 2 which are diamagnetic and square-planar. The diacetyl Schiff base of S-benzyldithiocarbazate behaves as a dinegatively charged quadridentate ligand forming neutral 1:1 complexes with nickel and copper(II). Magnetic and spectral data are in accord with a square-planar structure for these complexes.

PEROXO COMPLEXES OF ZIRCONIUM(IV), THORIUM(IV), MOLYBDENUM(VI), TUNGSTEN(VI) AND URANIUM(VI) IONS CONTAINING A QUADRIDENTATE SNNS SCHIFF BASE

Abstract Some new peroxo complexes of molybdenum, tungsten, uranium, zirconium and thorium containing quadridentate, dinegative Schiff base ligands have been synthesized and characterized. The Schiff bases C20H14N2O2H2 and C14H10N2O2H2 were derived from the condensation of o-phenylenediamine or hydrazine hydrate with salicylaldehyde, respectively. The Schiff bases undergo deprotonation, while complexation having ONNO donor sequences producing complexes of compositions [M(O)(O2)(ONNO)] and [M′(O2)(ONNO)] [M = MoVI, WVI and UVI; M′ = ZrIV and ThIV; ONNO = C20H14N2O22− and C14H10N2O22−]. The chelate effect of the quadridentate ligands stabilizes the metal-peroxo moiety which prevents oxygen transfer reactions to both organic and inorganic substrates. The σ-donor nature of the quadridentate ligands influences the mode of coordination of the peroxo moiety. The frequency of the ν1, mode of the M(O2) grouping decreases with an increase in the atomic number of the metals in a particular group.

Peroxo complexes of chromium(VI), molybdenum(VI), tungsten(VI) and zirconium(IV) ions containing tridentate and quadridentate neutral ligands

Abstract Several organoperoxo complexes of compositions [M(O) 2 (O 2 )(L)] [M = Cr VI , Mo VI and W VI ; L = diethylene triamine(det), 2,2,2-triethylenetetraamine(tet) and 2,3,2-triethylenetetraamine (2,3,2-tet)] and [Zr(O)(O 2 )(2,3,2-tet)] have been synthesized and characterized. These complexes were all non-electrolytes in DMSO and inert towards oxidation. The IR spectral data indicate that the ν 1 ,(O—O) stretching mode decreases with the increase in atomic number of metals in a group.

Some organoperoxo complexes of molybdenum and tungsten

Abstract Several new peroxo complexes of molybdenum and tungsten containing different organic ligands have been prepared. The complexes have the compositions [Mo(O)(O2)L2], [Mo(O)2(O2)L(H3O)]+, [Mo(O)(O2)L′] and [W(O)(O2)L2] [L = oxoquinolino, aniline-2- carboxylate, 2-aminophenoxide, picolinato or 2-carboxylatoquinolino ligand; L′ = N-(2- oxophenyl)salicylidenimino ligand], respectively. The complexes were found to oxidize allyl alcohol, and also PPh3 and AsPh3, to their oxides. The IR spectra of the complexes indicate that the frequency of the v1-mode of the M(O2) grouping, which is essentially an OO stretch, decreases with the increase in atomic number of metals in a particular group.

Peroxo complexes of ZrIV, ThIV, WVI and UVI ions stabilized by multidentate organic ligands

Abstract Several new peroxo complexes of zirconium, thorium, tungsten and uranium containing organic ligands, ethylenediaminetetraacetic acid and succinic acid, have been prepared. The complexes have the compositions [M(O 2 )(H 2 edta)], [M′(O)(O 2 )(H 2 edta)l and [M″(O 2 )(scac)·2L] (H 2 edta = dianion of ethylenediaminetetraacetic acid; scac = dianion of succinic acid; M = Zr IV and Th IV ; M′ = W VI and U VI ; M″ = Zr IV and Th IV ; L = OPPh 3 or OAsPh 3 ), respectively. The present complexes were found to be very stable and inert towards oxidation. The size of the metals as well as the electronic nature of the auxiliary ligands (L) influence the mode of coordination of the peroxo moiety. The frequency of the ν 1 mode of the M(O 2 ) grouping decreases with an increase in the atomic numbers of metals in a particular group and in donor strength of the ancillary ligands used.

COMPLEXES OF TRANSITION AND NONTRANSITION METALS OF DITHIOCARBAZATE ION AND THEIR BIOLOGICAL ACTIVITIES

The complexation of the dithiocarbazate ion (DTCA−) with various metal ions, viz., Sn(II)/(IV), Bi(III), Sb(III), U(VI), Zr(IV), Th(IV), Al(III), Ni(II), Zn(II), and Cu(II) was investigated. Most of the complexes were hexa-coordinated with the exception of Cu(II), Ni(II), and Zn(II) complexes that were four-coordinated. The biological properties of the metal complexes revealed that in general the complexes of nontransition metals were more effective against microorganisms than those of transition metals. In particular, [Sb(DTCA)Cl2·2H2O] and [Al(DTCA)Cl2·2H2O] were found to have strong antimicrobial activities. A minimum inhibitory concentration of 300 μg/mL was recorded for the above two complexes against Pseudomonas aeruginosa while that against Bacillus cereus was found to be 700 μg/mL. None of the complexes were cytotoxic.

1,2-Dibenzoylhydrazine

In the crystal structure of the title compound, C(14)H(12)N(2)O(2), the molecule lies about a twofold axis; two carbonyl groups and the H atoms of the N-N bond are in a trans orientation with respect to each other. In the crystal, each molecule is linked to the other and vice versa by intermolecular N-H.O hydrogen bonds between the amide hydrogen and the O atoms of neighbouring molecules to form two ten-membered rings, each of which has the graph-set motif C4R(2)(2)(10). This extends as a polymeric chain along the c axis.

Peroxo complexes of ZrIV, ThIV, MoVI and UVI ions containing some bidentate organic ligands

Abstract Several new organoperoxo complexes of Zr IV , Th IV , Mo IV and U VI have been synthesized and characterized. The complexes have the general formulae, [Zr(O 2 )C 6 H 4 (CO 2 ) 2 ·.2C 5 H 5 NO], [Th(O 2 ) 2 L], [Th(O 2 )C 6 H 4 (CO 2 ) 2 ·.2OPPh 3 ], [Th(O 2 )L′ 2 ], [MO(O 2 ) 2 L], [MO(O 2 )L′ 2 ] and [MO(O 2 )L″H 2 O] [L = bidentate, neutral; L′ = bidentate, uninegative and L″ = bidentate, dinegative ligands; M = Mo VI and U VI ], respectively. The complexes were found to oxidize PPh 3 and AsPh 3 to their oxides. The IR spectra of the complexes indicate that the frequency of the ν 1 mode of the M(O 2 ) grouping, which is essentially an OO stretch, decreases with the increase in the atomic number of metals in a particular group.