Complexes of cobalt(II), nickel(II), copper(II), cadmium(II), and mercury(II) with tetradentate Schiff base ligands

Summary A series of metal complexes with three new tetradentate Schiff bases derived from benzoin and benzil withc-toluidine and benzil with diaminoethane have been prepared and characterised by physical and chemical methods. The modes of bonding of the ligands with the metal ions have been proposed. Electronic spectra and room temperature magnetic moment values suggest octahedral geometry for the Co^II and Ni^II complexes, whereas the Hg^II and Cd^II complexes have tetrahedral geometry. The Cu^II complexes are square planar. Apart from the complexes of the Schiff bases derived from benzoin, all the other complexes have high molar conductance values suggesting them to be electrolytes. The complexes have been screened against some fungal pathogens.     

Spectroscopic Characterization and Biological Activity of Salicylaldehyde Thiazolyl Hydrazone Ligands and their Metal Complexes

Two novel bidentate Schiff base ligands, 2-(2-hydroxy-3,5-dichloro/diboromo) benzaldehyde-[4-(3-methyl-3-mesitylcyclobutyl)-1,3-thiazol-2-yl]hydrazone, L¹H, L²H and their transition metal complexes are reported. The new ligands and their complexes have been characterized by elemental analyses, Λ_M, infrared, u.v.–vis, ¹H- and ¹³C-n.m.r. spectroscopy, and magnetic susceptibility measurements. The thermal properties of all complexes have been investigated by TG technique. The complexes contain two monoanionic, bidentate NO ligands. It was found that all the complexes are mononuclear. Antimicrobial activities of the ligands and their complexes have been tested against five different microorganisms, and some of the complexes were found to be active against some of the microorganisms studied.     

Complexes of platinum,rhodium, iridium and ruthenium with a thiosemicarbazone derived from thiophene-2-carboxaldehyde

Summary Complexes of thiophene-2-carboxaldehyde thiosemicarbazone with Ru^III, Rh^III, Ir^III and Pt^IV have been prepared and characterized by elemental analyses, molar conductance, room temperature, magnetic moments, infrared and electronic spectral studies. Probable structures for the complexes are suggested. All are diamagnetic except the Ru^III complexes and possess octahedral structures. The crystal field parameters of the complexes have also been calculated.     

Synthesis,characterization and antimicrobial activity of the Schiff bases derived from 2,4-disubstituted thiazoles and 3-methoxysalicylaldehyde,and their cobalt(II), copper(II), nickel(II) and zinc(II) complexes

Two new Schiff base ligands containing 2,4–disubstituted thiazoles and cyclobutane rings, 4-(1-methyl-1-phenylcyclobutane-3-yl)-2-(2-hydroxy-3-methoxybenzylidenehydrazino)thiazole (L¹H), 4-(1-methyl-1-p-xylylcyclobutane-3-yl)-2-(2-hydroxy-3-methoxybenzylidenehydrazino)thiazole (L²H) and their mononuclear complexes with a 1:2 metal–ligand ratio have been prepared from acetate salts of Co^II, Cu^II, Ni^II and Zn^II in EtOH. The authenticity of the ligands and their complexes have been established by microanalyses, i.r., ¹³C- and ¹H-n.m.r. spectra, and by magnetic susceptibility and conductivity measurements. The complexes are mononuclear. Thermal properties of the ligands and complexes have been studied by t.g.a. and d.s.c. techniques. Antimicrobial activities of the ligands and their complexes have been tested against six different microorganisms; three are yeast and three are bacteria. One of the ligands and many of the complexes were found to be active against some of the microorganisms studied.     

Synthesis,characterization, photophysical,and redox properties of three trinuclear Ru(II) polypyridyl complexes possessing 5-amino-1,10-phenanthroline ligands

Three ruthenium(II) polypyridyl complexes with 5-amino-1,10-phenanthroline ligands have been successfully designed and synthesized. They have been fully characterized by ESI-MS, ESI-HRMS, ¹H NMR, and elemental analyses. The photophysical and electrochemical properties of the three complexes have been investigated in organic solvent. The geometrical configuration and the electron density distribution in the frontier molecular orbitals of the three complexes have been studied. The three complexes show metal-to-ligand charge transfer (¹MLCT) absorption at 445 nm, and intense triplet metal-to-ligand (³MLCT) emission at around 619 nm in fluid solution at 298 K and 580 nm in low-temperature glass. Electrochemical studies of the three complexes are consistent with one Ru^III/II reversible couple at around 1.31 V accompanied by three ligand-centered reduction couples.

     

Synthesis,Spectroscopic Studies,and In Vitro Antifungal Activity of Organosilicon(IV) and Organotin(IV) Complexes of 4-Amino-5-mercapto-3-methyl-S-triazole Schiff Bases

The Schiff bases derived from condensation of s-triazole with heterocyclic aldehydes and their 1:1 and 1:2 complexes have been synthesized. These complexes have been characterized by elemental analyses, molar conductance and spectroscopic studies, including UV, IR, ¹H, ¹³C, ²⁹Si, and ¹¹⁹Sn NMR spectroscopy. On the basis of these studies, the resulting complexes have been proposed to have trigonal bipyramidal and octahedral geometries. The biological activity of these complexes against various fungi has been investigated.     

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.     

Synthesis, characterization, catalytic, electrochemical and thermal properties of tetradentate Schiff base complexes

In this study, the Schiff base ligands H₂L¹–H₂L³ and their Cu^II, Co^II, Ni^II, Fe^III Ru^III and VO^IV complexes have been prepared and characterized by spectroscopic and analytical techniques. All the complexes are mononuclear. Keto-enol tautomeric forms of the ligands have been investigated in polar and apolar solvents. The ligands favor the keto-form in the C₇H₈ and C₆H₁₄. The C–C coupling reaction of the 2,6-di-t-butylphenol has been investigated by the Co^II and Cu^II complexes. Thermal properties of the complexes have been assessed using thermal techniques and similar properties were found. In the Fe^III and Ru^III complexes, firstly, the coordinated water molecule is lost from the complex; in the second step, the chloride ion leaves the molecule in the 300–350 °C temperature range. Finally, the complexes decompose to the appropriate metal oxide at the higher temperature ranges. The electrochemical properties of the complexes have been studied in the two different solvents (DMF and CH₃CN).     

Electron spin resonance spectroscopy of iron nitrosyl complexes with organic ligands

ESR spectra of liquid and frozen solutions of nitrosyl iron complexes formed in aqueous solution with a variety of mercaptans, dithiocarbamates and azoles have been studied. The hyperfine ¹⁴N splittings from nitrosyl groups and azole nitrogen as well as ¹H splittings in the case of nitrosyl mercaptan complexes have been observed. Structures of these complexes are suggested on the basis of the ESR spectral parameters.     

Polymerization and oxidation of pyrrole by organic electron acceptors

Simultaneous chemical polymerization and oxidation of pyrrole have been initiated by organic electron acceptors, 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and tetrachloro-o-benzoquinone(chloranil). The polypyrrole (PPY) complexes so produced are semiconductive and granular in nature. For the PPY–DDQ and PPY–chloranil complexes obtained from bulk polymerization, the respective electrical conductivities (σ) are of the order of 10^?1 and 10^?3 ohm^?1 cm^?1. However, σ is substantially lower for the complexes prepared in solvent media. Both complexes are relatively stable in the atmosphere. Thin uniform films of the PPY–organic acceptor complexes have also been synthesized on SnO₂ electrode by electrochemical polymerization in acetonitrile. The physicochemical properties of the PPY–organic acceptor complexes prepared chemically under the various experimental conditions are examined in detail.     

Binuclear complexes of Pt(II) with platinated 2-phenylbenzothiazole and bridged derivatives of pyridin- and benzothiazol-2-thiols

Binuclear complexes of Pt(II) cycloplatinated with 2-phenylbenzothiazole and bridging ligands have been shown to contain the Pt-Pt bond. The complexes have been studied by X-ray diffraction, ¹H NMR and electronic absorption spectroscopy, and electrochemical methods. The complexes cis-N_(bt),S-isomers with antisymmetric positions of the cyclometalated and the bridging ligands have been detected in the crystals as well as in the solutions. The low-wavelength absorption and luminescence of the complexes have been assigned to the metal-metal-ligand charge transfer. The two-electron oxidation and reduction waves in the voltamperograms are associated with the metal- and the ligand-centered processes, respectively.     

Complexes of morin and quercetin with boric acid and oxalic acid in acetic acid medium. Fluorimetric determination of boron

The binary and ternary fluorescent complexes of morin or quercetin with boric acid and oxalic acid in an anhydrous acetic acid medium are described. The physico-chemical and spectral properties and chemical composition of these complexes have been established. The ternary complexes are suitable for fluorimetric determinations of boron. The limits of detection are 0.1 ng B ml^-1 and 0.3 ng B ml^-1, for the morin and quercetin complexes, respectively, and calibration graphs are linear up to 10 μg B ml^-1.     

Transition metal complexes of 2-Carbethoxypyridine (Ethyl picolinate)

Summary A variety of metal(II) complexes of 2-carbethoxypyridine (L) have been prepared and characterised. With metal(II) chlorides the bis complexes can be formulated [ML₂Cl₂]^o (M=Cu^II, Ni^II, Co^II, Fe^II or Mn^II). The complexes are six-coordinate with 2-carbethoxypyridine acting as a bidentate ligandvia the pyridine nitrogen and the carbonyl group of the ester. The chloro complexes are nonelectrolytes in nitroethane; magnetic susceptibility measurements, i.r. and d-d electronic spectra are reported. With metal(II) perchlorate salts the complexes can be formulated as six-coordinate [ML₂ (OH₂)₂] [ClO₄]₂ species containing ionic perchlorate. The ester exchanges of some of these complexes with a variety of primary alcohols have been investigated.     

Cobalt(II), copper(II), nickel(II) and zinc(II) complexes of two novel Schiff base ligands and their antimicrobial activity

Two new, Schiff base ligands containing cyclobutane and thiazole rings, 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-(2,4-dihydroxybenzylidenehydrazino)thiazole (L¹H) and 4-(1-methyl-1-mesitycyclobutane-3-yl)-2-(2-hydroxy-3-methoxybenzylidenehydrazino)thiazole (L²H) and their mononuclear complexes with a 1:2 metal-ligand ratio have been prepared with acetate salts of Co^II, Cu^II, Ni^II and Zn^II in EtOH. The structures of the ligands and their complexes have been established by microanalyses, i.r., u.v.–vis., ¹³C- and ¹H-n.m.r. spectra, and by magnetic susceptibility measurements. The complexes are mononuclear. Thermal properties of the ligands and complexes have been studied by t.g.a. and d.s.c. techniques. Antimicrobial activities of the ligands and their complexes have been tested against eight different microorganisms. Some of the complexes and L¹H were found to be active against some of the microorganisms studied.     

Coordination properties of new indazole derivatives

Summary The bidentate nitrogen donor ligands 2-(1-indazolyl) pyridine and 2-(1-indazolyl) pyrimidine have been synthesised. Their complexes with Mn^II, Co^II, Ni^II, Cu^II and Zn^II have been prepared and characterised by elemental analysis, i.r., u.v. spectra and magnetic susceptibility measurements. The complexes are nonelectrolytes and have magnetic moments consistent with an octahedral environment.     

Synthesis,spectral, thermal and electrochemical characterization of metal(II) complexes with 1-S-methylcarbodithioate-4-substituted thiosemicarbazides

1-S-Methylcarbodithioate-4-substituted thiosemicarbazides (L¹-L³) have been prepared and confirmed by spectral data and elemental analysis. Co(II), Ni(II), Cu(II), Cd(II) and Zn(II) complexes with L¹-L³ have been prepared and characterized by elemental and thermal analyses, molar conductance, magnetic moment, as well as spectral data (IR, ¹H NMR, mass and electronic spectra). The molar conductance data reveal that the chelates are non-electrolytes. The IR and ¹H NMR spectra showed that L¹-L³ are deprotonated in the complexes and act as binegative SNNS donors. The electronic spectra of the complexes as well as their magnetic moments provide information about geometries. Thermogravimetric analysis of some complexes suggests different decomposition steps and ending with metal sulfide as final product. The redox properties of the complexes are explored by cyclic voltammetry.     

Spectral nature,antifungal activity and molecular structure of metal complexes of acetylpyrazine 4N-substituted thiosemicarbazones

Summary Nickel(II) and copper(II) complexes of acetylpyrazine 3-azabicyclo[3.2.2]-nonylthiosemicarbazone and nickel(II) complexes of acetylpyrazine ⁴N-methyl-, ⁴N-dimethyl-, and 3-hexamethyleneiminylthiosemicarbazone have been synthesized and characterized by their spectral and physical properties. Crystal structures for the nickel(II) complexes of the ⁴N-methyl- and ⁴N-dimethyl-derivatives, with a chloro ligand in the fourth coordination position, are included. The growth inhibition by the four thiosemicarbazones and their metal complexes against two human pathogenic fungi, Aspergillus niger and Paecilomyces variotii, have been evaluated.     

Biologically potent sulphonamide imine complexes of organotin(IV): Synthesis, spectroscopic characterization and biological screening

Coordination behaviour of a biologically potent sulphonamide-imine having N^∩N donor moiety towards the diorgano and triorganotin(IV) have been investigated. The unimolar and bimolar reactions of di-and triorgano-tin(IV) chlorides with monobasic bidentate imine resulted in the formation of colored solids, soluble in DMSO, DMF and MeOH, which have been characterized by elemental analyses, molecular weight determinations and conductance measurements. Structures of the resulting complexes have been proposed using IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectral studies. All the complexes are monomeric in nature as indicated by their molecular weight determinations. Conductivity measurements in dry DMF show them to be non-electrolytes. The pathogenicity and virulence of certain microbial infections associated with ions of the complexes have been found to be potent and like broad spectrum antibiotics. These results made it desirable to delineate a comparison between the ligand and its metal complexes. Emphasis has been given to the nematicidal properties.     

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.     

Convenient,mild and rapid synthesis and characterization of some Schiff-base ligands and their complexes with uranyl(II) ion

Some Schiff-base complexes of UO₂(II) ion derived from 2-hydroxyacetophenone and aliphatic diamines under reflux conditions have been synthesized. The resulting ligands and their complexes have been characterized by elemental analyses (C, H, N), infrared, ¹H NMR, ¹³C NMR and mass spectra. In these efficient reactions, Schiff-base complexes with important applications in analytical and organic chemistry are prepared.