SYNTHESIS AND SPECTROSCOPIC STUDIES OF SOME FUNGITOXIC ORGANOLEAD(IV) COMPLEXES OF SULFUR AND NITROGEN DONOR LIGANDS

Abstract

Some organolead(IV) complexes derived from biologically active sulfur and nitrogen donor ligands have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The trigonal bipyramidal and octahedral geometries for these complexes have been proposed on the basis of electronic, infrared and NMR (¹H and ¹³C) spectral evidences. The antifungal activity of some of the ligands and their complexes have also been evaluated against Fursarium oxysporum SCW. ex Frics f. sp. Ciceri (Pedwick) subram.     

New metal complexes derived from S-benzyldithiocarbazate (SBDTC) and chromone-3-carboxaldehyde: synthesis,characterization, antimicrobial,antitumor activity and DFT calculations

Novel monobasic tridentate ONS donor ligand (HL) was synthesized from the condensation reaction of chromone-3-carboxaldehyde with S-benzyldithiocarbazate (SBDTC). Reaction of the ligand with the metal ions copper(II), nickel(II), cobalt(II), oxidovanadium(IV), cerium(III), manganese(II), zinc(II), and cadmium(II) afforded dimeric complexes with the general formula [ML(Y)_m(H₂O)_x]₂·(Y)_m·nH₂O·zCH₃OH, Y?=?NO₃ or Cl, m?=?0–2, x?=?0–2, n?=?0–2, and z?=?0–1 for all complexes except oxidovanadium(IV) complex which has the formula [VOL(H₂O)]₂(SO₄). Structures of the ligand and its metal complexes were established through elemental, spectroscopic data (FT-IR, UV-Vis, and mass), thermal analyses, as well as conductivity and magnetic susceptibility measurements. The geometrical structures of the metal complexes are octahedral and square planar. The ligand and its complexes were subjected to in vitro bioassays against the gram-negative and gram-positive bacteria and the fungus strain with good results for some of these compounds. The antitumor activity of the ligand and its copper(II) and oxidovanadium(IV) complexes were investigated against HepG2 cell line. The molecular parameters of the ligand and its metal complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program, and computed data were correlated with the experimental results. The HOMO→LUMO electron transition potentially occurs from S-benzyldithiocarbazate to chromone moieties with 4.048?eV. The Mn(II) complex has the highest value of energy barrier, while Cu(II) complex has the lowest value among the complexes. All synthesized complexes have energy gap lower than free ligand and therefore these complexes are more reactive than the free ligand.     

Structural,spectroscopic, and biological aspects of S∩N donor Schiff-base ligands and their chromium(III) complexes

New chromium(III) complexes are synthesized by classical thermal and microwave (MW)-irradiated techniques. The Schiff bases 2-acetylfuran-S-benzyldithiocarbazate (L¹H), 2-acetylthiophene-S-benzyldithiocarbazate (L²H), 2-acetylpyridine-S-benzyldithiocarbazate (L³H), and 2-acetylnaphthalene-S-benzyldithiocarbazate (L⁴H) were prepared by condensation of -S-benzyldithiocarbazate in ethanol with the respective ketones by using MW as well as conventional methods. The chromium(III) complexes have been prepared by mixing CrCl₃ · 6H₂O in 1 : 1 and 1 : 2 molar ratios with monofunctional bidentate ketimines. The structure of the ligands and their transition metal complexes were confirmed by elemental analysis, melting point determinations, molecular weight determinations, infrared (IR), electronic and electron paramagnetic resonance (EPR) spectral, and X-ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode by S∩N donors. Thus, an octahedral environment around the chromium(III) has been proposed. The growth inhibiting potential of the ligands and complexes has been assessed against a variety of fungal and bacterial strains.     

Preparation and structural characterization of nickel(II), cobalt(II), zinc(II) and tin(IV) complexes of the isatin Schiff bases of S-methyl and S-benzyldithiocarbazates

The molecular structures of the isatin Schiff bases of S-methyldithiocarbazate (Hisasme) and S-benzyldithiocarbazate (Hisasbz) have been determined by X-ray diffraction and their complexes of general formula [ML₂]·n(solvate) [M = Co²⁺, Ni²⁺, Zn²⁺; L = anionic forms of Hisasme or Hisasbz; solvate = DMF, DMSO; n = 1, 2] and [Sn(L)Ph₂Cl]·nMeOH (n = 0, 1) have been synthesized and characterized by a variety of physicochemical techniques and X-ray diffraction. The bis-ligand complexes, [Ni(isasbz)₂]·2DMSO and [Co(isasme)₂]·DMF have a six-coordinate, distorted octahedral geometry with the two uninegatively charged tridentate ONS ligands coordinated to the metal ions meridionally via the amide O-atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. By contrast, the crystal structure of [Zn(isasbz)₂]·2DMF shows a four-coordinate distorted tetrahedral geometry with the two Schiff bases coordinated as NS bidentate ligands via the azomethine nitrogen atoms and the thiolate sulfur atoms. Steric constraints of the rigid tridentate ligands lead to unusual ‘pseudo-coordination’ of the O-donors which occupy sites close to the metal but too distant to be considered as true coordinate bonds.The crystal structures of the tin(IV) complexes [SnLPh₂Cl]·nMeOH (L = isasme and isasbz; n = 0, 1) also show that the Schiff bases act as monoanionic bidentate NS chelating agents coordinating the tin(IV) ion via the azomethine nitrogen atoms and the thiolate sulfur atoms, the tin atom in each complex is five-coordinate with a highly distorted geometry intermediate of square pyramidal and trigonal bipyramidal. Again Sn?O contacts are weak and do not qualify as coordinate bonds.     

Chemically modified activated carbon with S-benzyldithiocarbazate as a new solid-phase extractant for preconcentration of mercury prior to ICP-AES determination

A new sorbent S-benzyldithiocarbazate (SBDTC) modified activated carbon (AC-SBDTC) was prepared and studied for preconcentration for trace mercury(II) prior to inductively coupled plasma atom emission spectrometry (ICP-AES). The experimental conditions were optimised with respect to different experimental parameters using both batch and column procedures in detail. The optimum pH value for the separation of Hg(II) on the new sorbent was 3, while the adsorption equilibrium was achieved in less than 5?min. Complete elution of the adsorbed metal ions from the sorbent surface was carried out using 5?mL of 0.25?mol?L^?1 of HCl and 2% CS(NH₂)₂. Common coexisting ions did not interfere with the determination. The maximum static adsorption capacity of the sorbent under optimum conditions was found to be 0.55?mmol?g^?1. The detection limit of the present method was found to be 0.09?ng?mL^?1, and the relative standard deviation (RSD) was lower than 2.0%. The procedure was validated by analysing the certified reference river sediment material (GBW 08301, China), the results obtained were in good agreement with standard values. This sorbent was successfully employed in the separation and preconcentration of trace Hg(II) from the natural water samples yielding 80-fold concentration factor.     

Self-assembling dicopper(II) complexes of di-2-pyridyl ketone Schiff base ligands derived from S-alkyldithiocarbazates

Condensation of di-2-pyridyl ketone with S-methyldithiocarbazate or S-benzyldithiocarbazate yields potentially bridging ligands of the form Py₂CNNHC(S)SR; Hdpksme (R = Me; the di-2-pyridyl ketone Schiff base of S-methyldithiocarbazate) and Hdpksbz (R = Bz; the di-2-pyridyl ketone Schiff base of S-benzyldithiocarbazate). Complexation of these ligands with Cu(II) in a 1:1 M ratio leads to the formation of dinuclear complexes of the general formula [Cu(NNNS)X]₂ (X = Cl⁻, NO₃⁻, H₂O). X-ray crystallographic structure determinations show that each ligand provides three donor atoms (NNS) in a meridional configuration to one metal, viz. one of the pyridine nitrogen atoms, the azomethine nitrogen atom and the thiolate sulfur, while the nitrogen atom of the second pyridyl group forms a bridge to another copper(II) ion within the dimer. The coordination geometry around each copper(II) ion is approximately square pyramidal, the basal plane of which is composed of one of the pyridine nitrogen atoms, the azomethine nitrogen atom and a chlorido, nitrato or aqua ligand. The apical position of the square pyramid is always occupied by the pyridine nitrogen atom of the second ligand.