Microwave assisted synthesis,characterization and biological evaluation of palladium and platinum complexes with azomethines

Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicarbazone (C₉H₁₃N₃OS₂ or L¹H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C₉H₁₃N₃OS or L²H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, ¹H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the complexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested.     

Studies on some oxovanadium(IV) complexes of acyl pyrazolone analogues

A series of novel bidentate pyrazolone based Schiff base ligands were synthesized by interaction of 4-benzoyl-3-methyl-1-(4′-methylphenyl)-2-pyrazolin-5-one with various aromatic amines like aniline, o-,m-,p-chloroaniline and o-,m-,p-toluidine in a ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR and ¹H NMR data. The molecular geometries of five of these ligands have been determined by single crystal X-ray study. Crystallographic study reveals that these ligands exist in the amine-one tautomeric form in the solid state. NMR study also suggests the existence of the amine-one form in solution at room temperature. Ab initio calculations for representative ligand HL¹ has been carried out to know the coordination site of the ligand. Novel vanadium Schiff base complexes of these ligands with general formula [OV(L^1–7)₂(H₂O)] have been prepared by interaction of aqueous solution of vanadyl sulfate pentahydrate with DMF solution of the appropriate ligands. The resulting complexes have been characterized on the basis of elemental analysis, vanadium determination, molar conductance and magnetic measurements, thermo gravimetric analysis, infrared and electronic spectral studies. Suitable distorted octahedral structures have been proposed for these complexes.     

Green synthesis of new Ge(IV) complexes with bio-potent ligands and their antimicrobial,DNA cleavage,and antioxidant activities

Green microwave supported synthesis, spectral, antimicrobial, DNA cleavage, and antioxidant studies of Ge(IV) complexes with bio-potent ligands, 1-acetylferrocenehydrazinecarboxamide (L¹H) and 1-acetylferrocenehydrazinecarbothioamide (L²H) have been carried out. The ligands and their respective complexes have been characterized on the basis of elemental analysis, IR, ¹H and ¹³C NMR spectra, and X-ray powder diffraction studies. The ligands are coordinated to the Ge(IV) via azomethine nitrogen and thiolic sulfur atom/ enolic oxygen atom. Both ligands and their complexes demonstrated appreciable fungicidal and bactericidal properties. The metal complexes demonstrated stronger antimicrobial than the respective free ligands. DNA cleavage activity of the complexes study revealed higher activity of the complexes than the ligands. Antioxidant activity of the complexes was tested for their hydrogen peroxide scavenging.     

Synthesis,Spectroscopic Characterization,and In Vitro Antimicrobial Potency of Sulfur-Bonded Complexes of Boron(III)

The present article describes the synthesis and characterization of tetracoordinated boron (III) complexes with monobasic bidentate ligands (L ¹ H, L ² H, L ³ H, L ⁴ H, L ⁵ H, and L ⁶ H) having the general formulae PhB(L)(OH) and PhB(L) ₂ . The 1:1 and 1:2 reactions of phenyl boronic acid with monobasic bidentate ligands resulted in the formation of colored solids. The complexes have been characterized by elemental analysis, molecular weight determinations, and IR and NMR ( ¹ H, ¹³ C and ¹¹ B) spectroscopy, as well as UV-vis spectral studies. Based on these studies, a tetrahedral geometry has been proposed for the resulting complexes. The ligands, along with their complexes, have been screened in vitro against a number of pathogenic fungal and bacterial strains. The studies indicate that the boron chelates are more potent than the parent ligands.     

Synthetic, structural, and antimicrobial studies of organotin(IV) complexes of semicarbazone, thiosemicarbazone derived from 4-hydroxy-3-methoxybenzaldehyde

Reaction of dibutyltin dichloride, dimethyltin dichloride, and tributyltin chloride with ligands derived from thiosemicarbazone and semicarbazone leads to the formation of a new series of organotin(IV) complexes of general formula R₂SnCl₂·L and R₃SnCl·L (where L ligands derived from the condensation of thiosemicarbazide and semicarbazide with 4-hydroxy-3-methoxybenzaldehyde). The authenticity of these ligands and their metal complexes have been established on the basis of elemental analysis, conductance measurements, molecular weight determinations, infrared, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR, and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a bidentate. An octahedral structure is proposed for the organotin(IV) complexes. The ligands and its metal complexes are screened for their antimicrobial activities against some Gram-positive and Gram-negative bacteria, and fungus. The studies demonstrated that metalation can increase the antimicrobial activity rather than the free ligands.     

Synthesis,Structural, and Antibacterial Studies of Some Mixed Ligand Complexes of Zn(II), Cd(II), and Hg(II) Derived From Citral Thiosemicarbazone and N-Phthaloyl Amino Acids

A series of new mixed ligand complexes of Zn(II), Cd(II), and Hg(II) with cis-3,7-dimethyl-2,6-octadienthiosemicarbazone (CDOTSC; LH) and N-phthaloyl amino acids (AH) have been synthesized by the reaction of metal dichloride with ligands CDOTSC and N-phthaloyl derivative of DL-glycine (A₁H), L-alanine (A₂H), or L-valine (A₃H) in a 1:1:1 molar ratio in dry refluxing ethanol. All the isolated complexes have the general composition [M(L)(A)]. The plausible structure of these newly synthesized complexes has been proposed on the basis of elemental analyses, molar conductances, molecular weight measurement, and various spectral (IR, ¹H NMR, and ¹³C NMR) studies, and four coordinated geometries have been assigned to these complexes. All the complexes and ligands have been screened for their antibacterial activity.     

Antimicrobial,antifertility, and antiradiation studies of Ga(III) and Tl(I) complexes with N∩S and N ∩ O donor systems

New complexes of gallium(III) and thallium(I) derived from 5,6-dimethyl-1H-indol-2,3-dione hydrazinecarbothioamide (L¹H) and 5,6-dimethyl-1H-indol-2,3-dione hydrazinecarboxamide (L²H) have been prepared and investigated using a combination of microanalytical analysis, melting point, molar conductance measurement, electronic, IR, ¹H NMR, and ¹³C NMR spectral studies. Gallium isopropoxide interacts with the ligands in 1 : 1, 1 : 2, and 1 : 3 molar ratios resulting in the formation of colored products, whereas TlCl forms only unimolar products. The mono- and bis-alkoxy derivatives are dimeric, while the tris ligand metal complexes are monomeric. On the basis of conductance and spectral evidences, a pentacoordinate structure for gallium(III) 1 : 1 complexes, hexacoordinate structure for 1 : 2 and 1 : 3 complexes, and a bicoordinate geometry for thallium(I) complexes have been assigned. The ligands are coordinated to gallium(III) and thallium(I) via the azomethine nitrogen and the thiolic sulfur/enolic oxygen. The antimicrobial activities of the ligands and complexes have been screened in vitro against bacteria Pseudomonas cepacicola and Bacillus subtilis and fungi Collectatrichum capsici and Fusarium oxysporum. The complexes have higher activities than the free bases. In vivo studies of the ligands and their corresponding complexes have also been carried out to assess their antifertility and antiradiation activities. The results of these activities indicate the antiandrogenic and radiation protective nature of these complexes.     

DNA cleavage and antimicrobial studies of 17-membered schiff base macrocyclic triazoles: synthesis and spectroscopic approach

A novel series of 17-membered complexes [MLCl₂] (M = Co²⁺, Ni²⁺ and Cu²⁺) have been synthesized with newly derived biologically active ligands (L^I–L^IV). These ligands were synthesized by the condensation of 3-subtituted-4-amino-5-hydrazino-1,2,4-triazole with bis(phthalaldehyde)ethylenediamine precursor. The structure of the complexes has been proposed by elemental analyses, IR, EPR, electronic spectral studies, conductivity, magnetic, thermal and electrochemical studies. All the complexes are soluble in DMF and DMSO and are non-electrolytes. All these Schiff bases and their complexes have been screened for their antibacterial (Escherichia coli, Staphylococus aureus, Salmonella typhi, Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and Cladosporium) by the Agar and Potato dextrose agar diffusion method. The DNA cleavage study was done by Agarose gel electrophoresis technique.     

Synthesis,characterization, DNA binding,DNA cleavage,antioxidant and in vitro cytotoxicity studies of ruthenium(II) complexes containing hydrazone ligands

The synthesis, spectral characterization, and biological studies of ruthenium(II) hydrazone complexes [RuCl(CO)(PPh₃)₂L] (where L = hydrazone ligands) have been carried out. The hydrazones are monobasic bidentate ligands with O and N as the donors and are preferably found in the enol form in all the complexes. The molecular structure of the ligands HL¹, HL²_, and HL³ were determined by single-crystal X-ray diffraction. The DNA binding studies of the ligands and complexes were carried out by absorption spectroscopic and viscosity measurements. The results revealed that the ligands and complexes bind to DNA via intercalation. The DNA cleavage activity of the complexes, evaluated by gel electrophoresis assay, revealed that the complexes are good DNA cleaving agents. The antioxidant properties of the complexes were evaluated against DPPH, OH, and NO radicals, which showed that the complexes have strong radical-scavenging. Further, the in vitro cytotoxic effect of the complexes examined on HeLa and MCF-7 cancer cell lines showed that the complexes exhibited significant anticancer activity.     

Antimicrobial and DNA Cleavage Studies of New N2O2 Diazadioxa Macrocyclic Schiff Base Co(II), Ni(II) and Cu(II) Complexes Containing Triazole Head Unit: Synthesis and Spectroscopic Approach

A novel series of N₂O₂ diazadioxa macrocyclic complexes [MLCl₂] (M=Co²⁺, Ni²⁺ and Cu²⁺) have been synthesized with newly derived biologically active ligands (L^I-L^IV). These ligands were synthesized by the condensation of 1, 6-bis(2-formylphenyl)hexane and 3-subtituted-4-amino-5-hydrazino-1, 2, 4-triazole. The mode of bonding and overall geometry of the complexes have been inferred through IR, EPR, electronic spectral studies, conductivity, magnetic, thermal and electrochemical studies. All the complexes are soluble in DMF and DMSO and are non-electrolytes. All these complexes have been screened for their antibacterial (Escherichia coli, Staphylococus aureus, Salmonella typhi, Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and Cladosporium) by the MIC method. The DNA cleavage study was done by Agarose gel electrophoresis.     

Synthesis and characterization of two binuclear iron(III) complexes of aminoethanol derivatives of aminophenol as models for non-heme iron enzymes active sites

Two aminoethanol derivatives of aminophenol ligands were synthesized and characterized by IR and ¹H NMR spectroscopies. The binuclear iron(III) complexes of these ligands have been prepared and characterized by IR, ¹H NMR and UV-Vis spectroscopic techniques, cyclic voltammetry, single crystal X-ray diffraction and magnetic susceptibility studies. X-ray analysis revealed binuclear complexes, Fe₂(L₂), in which Fe(III) centers are surrounded by two phenolate and hydroxyl oxygen atoms, and amine nitrogens of the ligands. The metal active sites of both complexes are held together by the two above mentioned hydroxyl bridges. Variable temperature magnetic susceptibility indicates antiferromagnetic coupling between the iron centers of both complexes. This exchange coupling is stronger for Fe₂(L^ae)₂, such that it shows a room temperature strong coupling between the two iron centers. The investigated complexes undergo irreversible electrochemical oxidation and reduction.     

Mixed-ligand Copper(II) Complexes: Investigation of their Spectroscopic, Catalysis, Antimicrobial and Potentiometric Properties

Schiff base ligands HL¹–HL⁶ have been prepared from the reaction of 2,6-diformyl-4-t-butylphenol and 2,6-di-formyl-4-methylphenol with various aromatic amines in ethanolic solution. The Schiff base ligands 2,2′-dipyridine (dp) mixed-ligand Cu^II complexes have been obtained. Mixed-ligand Cu^II complexes containing the dp ligand have ionic nature and they conduct the electricity in solution media. The complexes have been obtained in two different forms: one of them is [Cu₂(Lⁿ)Cl₃] (n: 1, 2, 3, 4, 5 and 6) and other complexes have the general formula [Cu₂(Lⁿ)(dp)₂]3Cl. Ligands and their complexes have been characterized by elemental analyses, FT-IR, electronic spectra, molar conductance, ¹H(¹³C)-n.m.r. and mass spectral data. Their stoichiometric protonation constants have been determined potentiometrically in dioxan using a combined pH electrode at 25 °C, under a nitrogen atmosphere. For the calculation of the protonation constants, PKAS computer programme has been used. The effects of the substituents on the protonation constants and the additivities of these effects are discussed. The antimicrobial activity studies of the ligands and their complexes have been studied against the Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcuc faecalis, bacteria and Saccoramyces cerevisia, yeast. The catalytic properties of the complexes have been studied on the ascorbic acid, catechol and 2,6-di-t-butylphenol substrates. Thermal behaviour of the complexes has been studied by thermal techniques.     

Coordination chemistry of palladium(II) and platinum(II) complexes with bioactive Schiff bases: Synthetic,spectral, and biocidal aspects

The Schiff bases, 5-nitro-indol-2,3-dionehydrazinecarboxamide (HSCZ¹) and 7-nitro-indol-2,3- dionehydrazinecarboxamide (HSCZ²), have been synthesized by the condensation of 5-nitro-indol-2,3-dione and 7-nitro-1H-indol-2,3-dione with semicarbazide hydrochloride, respectively. The palladium(II) and platinum( II) complexes have been prepared by mixing palladium chloride and platinum chloride in 1: 2 molar ratios with monobasic bidentate Schiff bases. The ligands and complexes of palladium and platinum have been characterized by elemental analyses, melting point determinations, conductance measurements, molecular weight determinations, and IR, ¹H NMR, and UV spectral studies. These studies showed that the ligands coordinate to the metal atoms in a monobasic bidentate mode, coordinating through oxygen and nitrogen donor systems. Thus, a tetracoordinated environment around the metal atom has been proposed. Both the ligands and their complexes have been screened for their biological activity on several pathogenic fungi and bacteria and were found to possess appreciable fungicidal and bactericidal properties. Plant growth regulating activity of one of the ligands and its complexes has also been recorded on gram plant, and results have been discussed. The article is published in the original.     

Antimicrobial,antioxidant and SOD activities of copper(II) complexes derived from 2-aminobenzothiazole derivatives

A series of Cu(II) complexes have been synthesized from bidentate Schiff base ligands (by condensation of Knoevenagel condensate of acetoacetanilide (obtained from substituted benzaldehydes and acetoacetanilide) and 2-aminobenzothiazole). They were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, UV–vis., molar conductance, magnetic moment, ESR spectra and electrochemical studies. Based on the magnetic moment, ESR, and electronic spectral data, a distorted square planar geometry has been suggested for the complexes. Antibacterial and antifungal screening of the ligands and their complexes reveal that all the complexes show higher activities than the ligands. The antioxidant activities of the ligands and complexes were determined by superoxide and hydroxyl radical scavenging methods in vitro, indicating that the complexes exhibit more effective antioxidant activity than the ligands alone. The results show that the Cu(II) complexes also have similar superoxide dismutase activity to that of native Cu, Zn-SOD. All complexes exhibit suitable Cu(II)/Cu(I) redox potential (E_1/2) to act as synthetic antioxidant enzyme mimics.     

Sulfur-Bonded Coordination Compounds of Palladium(II) and Platinum(II) and Their Antimicrobial Activity

The synthetic, spectroscopic, and biological studies of some new palladium(II) and platinum(II) complexes derived from biologically active sulfur donor ligands 1H-indol-2,3-dione benzothiazoline (Bzt ₁ H) and 5-nitro-1H-indol-2,3-dione benzothiazoline (Bzt ₂ H) have been described. The reactions were carried out in 1:2 molar ratios. The authenticity of the benzothiazolines and their complexes has been established on the basis of elemental analyses; molecular weight determinations; and IR, ¹ H NMR, ¹³ C NMR, and UV spectral studies. Based on IR and ¹ H NMR spectral studies, a square-planar structure has been assigned to these complexes. Studies were conducted to assess the comparative growth inhibiting potential of the synthesized complexes against the benzothiazolines for a variety of fungal and bacterial strains. The studies demonstrate that the ligands and complexes possess antimicrobial properties. Further, it was noted that the growth-inhibiting potential of the complexes is greater than the parent benzothiazolines.     

Microwave-assisted synthesis of nitrogen-sulfur and nitrogen-oxygen donor ferrocene-containing ligands and their organotitanium(IV) and organozirconium(IV) complexes

The synthetic routes and spectroscopic studies of organotitanium(IV) and organozirconium(IV) complexes derived from azomethines, 1-acetylferrocenethiosemicarbazone (L¹H) and 1-acetylferrocenesemi-carbazone (L²H), have been carried out in 1 : 1 and 1 : 2 stoichiometric ratios. Azomethines and their complexes have been characterized by elemental analyses, conductance measurements, molecular weight determinations, and spectral studies. The electronic, IR, and ¹H NMR and ¹³C NMR spectral data indicate that azomethines act as bidentate ligands and coordinate to the metal (Ti or Zr) via nitrogen and the sulfur or oxygen atoms giving trigonal bipyramidal and octahedral geometries for the resulting complexes. All the ligands and their complexes have been screened for their biological activity on several pathogenic fungi and bacteria and were found positive in this respect. The text was submitted by the authors in English.     

Synthesis and characterization of coordination compounds of organotin(IV) with nitrogen and sulfur donor ligands

The reactions of dimethyltin dichloride with nitrogen and sulfur donor ligands derived by condensation of S‐benzyldithiocarbazate with indol‐3‐carboxylaldehyde, thiophene‐2‐aldehyde and furfuraldehyde have been investigated in 1:1 and 1:2 molar ratios in anhydrous alcohol. These ligands act as mononegatively charged bidentate species and coordinate to the central tin(IV) atom through the thiosulfur by proton exchange with the azomethine nitrogen. The newly synthesized complexes have been characterized by elemental analysis, conductance measurements and molecular weight determinations. The mode of bonding and the geometry of the complexes have been suggested on the basis of infrared, electronic and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, and probable structures have been assigned to these complexes. A few representative ligands and their tin(IV) complexes have also been screened for their antifungal and antibacterial activities and found to be quite active in this respect. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis and characterization of Schiff base metal complexes: their antimicrobial,genotoxicity and electrochemical properties

We have synthesized the three Schiff-base ligands H₂L¹–H₂L³ and their Co^II, Fe^III and Ru^III metal complexes. All compounds have been characterized by analytical and spectroscopic methods. Oxidation of cyclohexane has been done by the metal complexes in CH₃CN using H₂O₂ and/or t-butylhydroperoxide (TBHP) as a co-catalyst. The keto-enol tautomeric forms of the ligands have been studied in polar and non-polar organic solvents. Electrochemical properties of the complexes have been studied at different scan rates. Thermal studies were carried out for the compounds. The ligands H₂L¹–H₂L³ were mutagenic on Salmonella Typhimurium TA 98 strain in the presence and/or absence of S9 mix. While the ligands H₂L¹ and H₂L² showed mutagenic activity on the strain TA 100 with and without S9 mix, the ligand H₂L³ was not mutagenic for TA 100. Antimicrobial activity studies of the compounds have also been carried out.     

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.     

Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

The reaction of 2,2′:4,4′′:4′,4′′′‐quaterpyridyl (qtpy), with d⁶ ruthenium(II) (Ru^II), and rhenium(I) (Re^I) metal centers has been investigated. The pendant pyridyl groups on the products have also been methylated to produce a second series of complexes containing coordinated Meqtpy²⁺. The absorption spectra of the complexes are dominated by intraligand and charge‐transfer bands. The ruthenium(II) complexes display broad unstructured luminescence consistent with emission from a Ru(d)→diimine(π*) manifold in acetonitrile solutions. In aqueous solutions, their emissions are weaker and the lifetimes are shorter. This effect is particularly acute for complexes incorporating coordinated dipyridylpyrazine, dppz, ligands. Although the emission of the ruthenium(II) complexes containing Meqtpy²⁺ is generally shorter than their qtpy analogs, it is notable that solvent‐dependent effects are much less intense. The rhenium(I) complexes also display broad unstructured luminescence but, compared with the ruthenium(II) systems, they have a relatively short lifetime in acetonitrile. Electrochemical studies reveal that all of the Ru^II complexes display chemically reversible metal‐based oxidations. Re^I complexes only display irreversible metal‐based oxidations. In most cases, the reduction processes were not fully chemically reversible. The electrochemical and optical studies reveal that the nature of the lowest excited state of these complexes—particularly, the systems incorporating dppz—is highly dependent on the nature of the coordinated ligands. Calculations indicate that, although the excited state of most of the complexes is centered on the qtpy or Meqtpy²⁺ ligands, the excited state of the complexes containing dppz ligands is switched away from the dppz by qtpy methylation. A crystallographic study on one of the dicationic ruthenium(II) structures reveals that it forms an inclusion complex with benzene.