H. M. Parekh

Bactericidal activity of different oxovanadium(IV) complexes with Schiff bases and application of chelation theory

Oxovanadium(IV) complexes have been synthesized and characterized the general composition [VOL(A)], where H2L = salicylidene-o-aminothiophenol A1 = bis(benzylidene)ethylenediamine, A2 = bis(acetophenone)ethylenediamine, A3 = 2,2′-bipyridylamine, A4 = bis(benzylidene) − 1,8-diaminonaphthalene, A5 = thiophene-o-carboxaldeneaniline and A6 = thiophene-o-carboxaldene-p-anisidine. Spectral studies indicate that the oxovanadium(IV) complexes assume a six-coordinate octahedral geometry. The antibacterial activities of the complexes against Salmonella typhi, Escherichia coli and Serratia mercescens are higher as compared to the free ligands, vanadyl sulphate, and the control (DMSO) but of moderate activity as compared to the standard drug (tetracycline).

Preparation, characterization and toxic activity of oxovanadium(IV) mixed-ligand complexes

New oxovanadium(IV) mixed-ligand complexes of the general composition [VO(L)(A)], where KHL = potassium salt of salicylideneglycine, A1 = bis(benzylidene)ethylenediamine, A2 = bis (acetophenone)ethylenediamine, A3 = di(2-pyridyl)amine, A4 = bis(benzylidene)-1,8-diaminonaphthalene, A5 = thiophene-o-carboxaldene-aniline, A6 = thiophene-o-carboxaldene-p-anisidine, have been synthesized by the interaction of these ligands with vanadyl sulphate. The mixed-ligand complexes have been characterized on the basis of elemental analysis, magnetic measurements, electronic and infrared spectra. An octahedral structure has tentatively been assigned to all of the mixed-ligand complexes. The mixed-ligand complexes show higher toxic activity against the Salmonella typhi, Escherichia coli and Serratia mercescen as compared to the ligands, vanadyl sulphate and control (dimethyl sulphoxide). The mixed-ligand complexes were also tested against a standard drug (tetracycline).

Synthesis, structural characterization, and antifungal activity of schiff bases and their transition metal mixed-ligand complexes

Mixed-ligand complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been prepared with biologically active Schiff bases, viz. potassium salt of o-hydroxyacetophenoneglycine [KHL] and bis(benzylidene)ethylenediamine [A1] or thiophene-o-carboxaldene-p-toluidine [A2]. The synthesized mixed-ligand complexes have been characterized on the basis of elemental analysis, thermogravimetric analysis, magnetic measurements, and electronic and infrared spectra. The mixed-ligand complexes show higher antifungal activity as compared to the free ligands, metal salts, and the control (dimethylsulfoxide) but moderate activity as compared to the standard fungicides (bavistin and emcarb).

Synthesis, physicochemical characteristics, and biocidal activity of some transition metal mixed-ligand complexes with bidentate (NO and NN) Schiff bases

Mixed-ligand complexes of the type [M(SB)2acphen], where M = Mn(II), Co(II), Ni(II), Cu(II), and Cd(II), HSB = 3,5-dibromosalicylideneaniline, and acphen = bis(acetophenone)ethylenediamine, have been prepared and characterized on the basis of elemental analyses, magnetic measurements, thermogravimetry, and infrared and electronic absorption spectroscopy. All the mixed-ligand complexes exhibit an octahedral geometry. The mixed-ligand complexes show antimicrobial activities against bacteria, yeast, and fungi.

Polymeric Coordination Compounds Derived from Transition Metal(II) with Tetradentate Schiff‐base: Synthetic, Spectroscopic, Magnetic and Thermal Approach

The polymeric coordination compounds have been synthesized using the dipotassium salt of N,N′‐di(carboxymethylene)terephthalaldehydediimine (K2SB1) or N,N′‐di(carboxyethylene)terephthalaldehydediimine (K2SB2) with manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II). The ligands have been characterized by 1H‐NMR, and 13C‐NMR spectra. The polychelates have been characterized by elemental analyses, magnetic measurements, thermogravimetric analyses, electronic spectra and infrared spectra. The coordination compounds are colored, and the central metal ions are octahedrally coordinated with two water molecules and the Schiff bases. The Schiff bases act as di‐negative tetradentate ligands, in which bonding occurs through two oxygen and two nitrogen atoms. The polymers are insoluble in all common organic solvents such as acetone, methanol, ethanol, N,N‐dimethylformamide and dimethylsulfoxide.

Synthesis and antifungal activity of oxovanadium(IV) complexes with Schiff bases

A series of preparations are reported representing complexes between a range of ligands [KHL = potassium salt of salicylidene-β-alanine, A1 = 2,2′-bipyridylamine, A2 = bis(benzylidene)ethylenediamine, A3 = thiophene-o-carboxaldene-aniline, A4 = thiophene-o-carboxaldene-p-toluidine, A5 = bis(benzylidene)-1,8-diaminonaphthalene, A6 = bis(acetophenone)ethylenediamine] and oxovanadium(IV) ion. Relevant electronic (UV), infrared (IR) spectra, thermogravimetric analyses, elemental analyses, and magnetic measurements are reported and interpreted in terms of the metal ion coordination geometry and, where appropriate, the likely octahedral structures of the compounds. The complexes are paramagnetic in nature. The antifungal activity of the complexes against A. niger, F. oxysporum, and A. flavus species is reported. All the tested complexes show higher antifungal activity as compared to free ligands, vanadyl sulfate, and the control (DMSO), but moderate activity as compared to the reference fungicides bavistin and emcarb.

Synthesis, structural elucidation, electro-chemical behaviour and fungitoxic activity of transition metal(II) mixed-ligand complexes with some Schiff bases

The Schiff bases, potassium salt of salicylidene-β-alanine [KHL], bis(benzylidene)ethylenediamine [SB1] and thiophene-o-carboxaldene-p-toluidine [SB2], and mixed-ligand complexes with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been prepared. They were characterized by elemental analyses, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.), infrared spectra and electronic spectra. The mixed-ligand complexes were found to have the general composition [M(L)(SB)(H2O)]. All the mixed-ligand complexes were found to have six-coordinated octahedral geometry. The fungitoxic activity of the ligands, metal salts, control (DMSO), bavistin, emcarb, and mixed-ligand complexes were screened against Aspergillus niger, Fusarium oxysporum and Aspergillus flavus. All the mixed-ligand complexes show higher fungitoxic activity as compared to the Schiff bases, metal nitrate and control (dimethyl sulphoxide, DMSO), and moderate fungitoxic activity as compared to the fungicides (bavistin and emcarb).

In vitro fungitoxic activity of some Schiff bases and their oxovanadium(IV) complexes

The oxovanadium(IV) (VO(IV)) complexes, Schiff bases, vanadyl sulphate, standard fungicides (bavistin and emcarb) and control (dimethyl sulphoxide) were tested for their in vitro fungitoxic activity on A. niger, F. oxysporum and A. flavus. The oxovanadium(IV) complexes show higher fungitoxic activity as compared with the free ligands, vanadyl sulphate and control (dimethyl sulphoxide), but moderate fungitoxic activity as compared with the standard fungicides (bavistin and emcarb). Oxovanadium(IV) complexes have been prepared with biologically active Schiff bases viz. the potassium salt of salicylidene-DL-alanine (sal-ala), 2,2′-bipyridylamine (bipym), bis(benzylidene)ethylenediamine (benen), thiophene-o-carboxaldeneaniline (tca), thiophene-o-carboxaldene-p-toluidine (tct), bis(benzylidene)-1,8-diaminonaphthalene (bendan) or bis(acetophenone)ethylenediamine (acphen). They have been characterized on the basis of elemental analysis, thermogravimetric analysis, magnetic measurements, electronic and infrared spectra. An octahedral geometry has been tentatively assigned to all the complexes.

Coordination Polymeric Assemblies of some d‐Block Elements with Schiff Bases and its Characterization

A few coordination chain polymeric assemblies of the type [M(SB)(H2O)2]n [M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), H2SB1=1,1′‐dihydroxy‐2,2′‐(1‐isonitriloethylidyne ‐4‐nitrilomethylidenephenyl)diphenyl or H2SB2=1‐thio‐1′‐hydroxy‐2,2′‐(1‐isonitriloethylidyne‐4‐nitrilomethylidenephenyl)diphenyl have been investigated. Structural and spectroscopic properties have been studied on the basis of elemental analyses, infrared spectra, 1H‐NMR, 13C‐NMR, electronic spectra, magnetic measurements and thermogravimetric analyses. The Schiff bases act as binegative tetradentate ligands and bonding occur through the nitrogen and oxygen or sulfur atoms. An octahedral geometry has been assigned to all the prepared coordination polymers. The coordination polymers are insoluble in common organic solvents like benzene, acetone, ethyl acetate, methanol, ethanol, chloroform, dimethyl formamide and dimethyl sulphoxide.