Synthesis, characterization and antitumour activity of metal complexes of 5-carboxy-2-thiouracil

Metal complexes of 5-carboxy-2-thiouracil with Mn(ll), Co(ll), Ni(ll), Cu(ll), Zn(ll) and Cd(ll) ions were synthesized, characterized, and subjected to a screening system for evaluation of antitumour activity against Sarcoma-180 (S-180) tumour cells. The complexes were characterized by elemental analysis, infrared, electronic spectra, room temperature magnetic measurements and powder X-ray diffraction. The antitumour activity results indicate that some complexes have antitumour activity both in vivo and in vitro against S-180 tumour cells.     

Lanthanide complexes of new ditopic,tripodal macrocycles: synthetic,structural, stability and luminescence studies

Mannich reactions of salicylaldehyde with 1,4,7-triazacyclononane afford new ditopic, tripodal macrocycles that contain adjacent proton-binding and lanthanide-binding compartments; structural and stability studies illustrate the O₆-pendant compartments as metal-binding and the N₃-capping macrocyclic compartment as proton-binding while pH-modulated stabilities span the range Log 17–35. Luminescence of the Eu(III) and Tb(III) complexes is weak, as expected for complexes that include coordinated water.     

Conductometric studies of charge transfer complexes in solution

Conductometric study for formation of charge-transfer complexes, in the systems napthtalene: picric acid and biphenyl: picric acid in acetonitrile; and p-phenylendiamine:choloranil in acetone, methanol and acetonitrile yielded the stoichiometry of the napthalene:picric acid complex as 1:1 and that of the biphenyl:picric acid and p-phenylendediamine:chloranil complexes as 2:1. On dilution with inert solvent CCl₄μ_ν = A + Bm^{$\text{sol1}\text{2}$}_DA is found applicable but with positive slope. The positive values of B obtained are attributed to decreased ionization or/and enchanced ion pair formation with decrease in dielectric constant of the solvent medium.     

Electrodeposition of nanocrystalline CdSe thin films from dimethyl sulfoxide solution: Nucleation and growth mechanism, structural and optical studies

Cadmium selenide (CdSe) nanocrystalline semiconductor thin films have been synthesized by electrodeposition at controlled potential based in the electrochemical reduction process of molecular selenium in dimethyl sulfoxide (DMSO) solution. The nucleation and growth mechanism of this process has been studied. The XRD pattern shows a characteristic polycrystalline hexagonal wurtzite structure with a slight (1 0 1 0) crystallographic preferred orientation. The crystallite size of nanocrystalline CdSe thin films can be simply controlled by the electrodeposition potential. A quantum size effect is deduced from the correlation between the band gap energy and the crystallite size.     

Metal- and nonmetal-catalyzed synthesis of five-membered S,N-heterocycles

Due to significant biological activity associated with N-, O- and S-heterocycles, a number of reports for their synthesis have appeared in recent decades. The metal- and nonmetal-catalyzed synthesis of heterocycles is becoming an important and highly rewarding protocol in organic synthesis. This review summarizes the applications of metal and nonmetal as a catalyst for the synthesis of sulfur- and nitrogen-containing heterocycles. It describes the formation of five-membered heterocyclic rings.     

Metal complexes of diisopropylthiourea: synthesis, characterization and antibacterial studies

Co(II), Cu(II), Zn(II) and Fe(III) complexes of diisopropylthiourea have been synthesized and characterized by elemental analyses, molar conductivity, magnetic susceptibility, FTIR and electronic spectroscopy. The compounds are non-electrolytes in solution and spectroscopic data of the complexes are consistent with 4-coordinate geometry for the metal(II) complexes and six coordinate octahedral for Fe(III) complex. The complexes were screened for their antibacterial activities against six bacteria: Escherichia coli, Pseudomonas auriginosa, Klebsiella pneumoniae, Bacillus cereus, Staphylococcus aureus and Bacillus pumilus. The complexes showed varied antibacterial activities and their minimum inhibitory concentrations (MICs) were determined.     

Complexation and structural studies of a sulfonamide aza-15-crown-5 derivative

An aza-15-crown-5 derivative, N-[4-(phenyldiazo)benzenesulfonyl]-aza-15-crown-5, 1 was synthesised from commercially available starting materials in 55% yield. Compound 1, which contains a sulfonamide link between the crown ether macroring and the azobenzene, readily binds alkali metals in buffered ethanol–water (75:25 v/v, pH 6.66). Titration data for both sodium and potassium were readily fitted to a 1:1 metal ion/ligand binding model to obtain stability constants (log K) of 4.7 ± 0.4 and 4.8 ± 0.2 dm³ mol^? 1, respectively. We also investigated the structures of 1 and the sodium perchlorate salt of 1, [Na(1)(H₂O)]₂(ClO₄)₂, which were determined by X-ray crystallography. [Na(1)(H₂O)]₂(ClO₄)₂ is a dimer in the solid state whereby a sulfonamide oxygen atom from one of the [Na(1)(H₂O)] cations provides solvation of the adjacent macroring bound sodium cation. In the crystal structure, binding of a water molecule to the sodium cation is supported by hydrogen bonding to the sulfonamide oxygen, which represents a supramolecular lariat ether-like interaction.     

Triphenylamine substituted dipyrrinato metal complexes: Synthesis,optical and electrochemical studies

A series of triphenylamine substituted dipyrrinato metal complexes (1–8) have been synthesized. The mononuclear type complexes 1–6 have Ni(II), Co(II), Pd(II), In(III), and Zn(II) metal ions in the core. The binuclear type complexes 7 and 8 have Zn(II) metal ion in the center. All the compounds (1–8) were characterized by HRMS, NMR, IR, UV–vis absorption, cyclic voltammetry and fluorescence techniques. The presence of large electron rich triphenylamine moiety at dipyrrin ligands affected the spectral properties of complexes. Except Co(II) complex, other metal complexes exhibited blue shifted absorption maxima in UV–vis studies. The In(III) and Zn(II) metal complexes 4–6 showed red shifted emission maxima in fluorescence compared to their corresponding phenyl analogues. Complexes 3–8 exhibited good Stokes shifts in the range of 4600 to 7000 cm^− 1 with reduced quantum yields. Singlet state lifetimes of complexes 3–8 were in the range of 2 to 4 ns; also the decrease in radiative decay constants k_r and the increase in non-radiative decay constants k_nr were in line with the quantum yield data. CV studies of complexes 1–8 showed anodic shifts in the oxidation potentials, suggesting that meso-triphenylamine group has affected the electronic properties of complexes by making them difficult to oxidize.     

Catecholate complexes of zirconium: synthesis,spectroscopic characterization and polymerization studies

Varieties of new catecholate complexes containing zirconium were synthesized in high yields and purity. These derivatives are potent initiators for the ring‐opening polymerization (ROP) of rac‐lactide, l ‐lactide, ?‐caprolactone, δ‐valerolactone, rac‐β‐butyrolactone, ethylene and propylene. The number‐average molecular weights of the resulting polymers are slightly higher than the theoretical molecular weight and they have controlled molecular weight distributions. The isopropoxide moiety in these complexes is responsible for initiating the ROP. For ethylene and propylene polymerization, we were able to achieve good activity using methylaluminoxane as a co‐catalyst. © 2013 Society of Chemical Industry     

Two interesting tetranuclear Ag(I) complexes based on dipyrido[3,2-f:2,3-h]-quinoxaline: Synthesis,structural, luminescence and theoretical studies

Two new isostructural tetranuclear Ag(I) complexes, formulated as [AgX(Dpq)]₄ (X = I, 1; Br, 2; Dpq = dipyrido[3,2-f:2,3-h]-quinoxaline), were synthesized by slow diffusion method for the first time. The central portion of each structure consists of a (AgX)₄ core and is surrounded by four Dpq ligands. The Dpq units in the tetrameric structures are found to stack in almost parallel and display π–π stacking interactions. Moreover, Ag–Ag interactions are observed in both complexes (3.1505(7) Å for 1 and 3.1136(7) Å for 2). Density functional theory and time-dependent density functional theory calculations at the B3LYP/LanL2DZ* + 6-31G* level were performed on 1 and 2 to rationalize their experimental absorption spectra. Both complexes exhibit intense luminescence in ethanol solution at room temperature.     

Ultrafast X-ray absorption studies of the structural dynamics of molecular and biological systems in solution

We review our recent studies of excited state structures and dynamics of chemical and biological systems with pico- and femtosecond X-ray absorption spectroscopy in the liquid phase.     

Synthesis,characterization and antitumour studies of metal chelates of N1-isonicotinoyl-3-methyl-4-(p-hydroxybenzilidene)-2-pyrazolin-5-one

The cobalt(II), nickel(II) and copper(II) complexes of N-Isonicotinoyl-3-methyl-4-(p-hydroxybenzilidene)-2-pyrazolin-5-one (IMHBP) with different counter anions have been prepared and characterized. An octahedral geometry has been assigned to the cobalt(II) and nickel(II) complexes and a square-planar structure to the copper(II) complexes. IMHBP acts as a neutral bidentate ligand in all these complexes by coordinating through the oxygen atoms of the amide group and carbonyl at position-5. The other coordination sites are satisfied by anions alone or anions and water molecules. The ligand and the complexes were screened for their possible antitumour activity. The copper(II) complexes are appreciably active in reducing mice tumours.     

Synthesis,structural studies,and antimicrobial activity of polymeric copper(II) tetrathiocyanato diargentate(I) complexes with some acylhydrazones

Copper(II) complexes of the type Cu[Ag(SCN)₂]₂·L (where L is acetophenone benzoyl hydrazone, acetophenone isonicotinoyl hydrazone, acetophenone salicyloyl hydrazone, acetophenone anthraniloyl hydrazone, p‐hydroxyl acetophenone benzoylhydrazone, p‐hydroxyl acetophenone isonicotinoyl hydrazone, p‐hydroxyl acetophenone salicyloyl hydrazone, or p‐hydroxyl acetophenone anthraniloyl hydrazone) were synthesized and characterized. All the complexes were polymeric and insoluble in common organic solvent and were nonelectrolytes. The ligands were coordinated through >C?O and >C?N? groups. All the SCN groups present in the complexes acted as bridges between two metal centers, resulting in a polymeric structure of the Lewis acid Cu[Ag(SCN)₂]₂ as well as its complexes. Electronic and electron spin resonance spectra suggested a square planar geometry for the Lewis acid and an elongated tetragonally distorted octahedral geometry for all the complexes. The powder X‐ray diffraction parameters for acetophenone salicyloyl hydrazone and p‐hydroxyl acetophenone anthraniloyl hydrazone complexes corresponded to orthorhombic and tetragonal crystal lattices, respectively. The complexes showed a fair degree of antifungal activity against Rizoctonia sp., Aspergillus sp., and Stemphylium sp. and moderate antibacterial activity against Clostridium sp. (Gram‐positive) and Pseudomonas sp. (Gram‐negative). The complexes were more active than the parent ligands. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Silver(I) cis-diphenylphosphinoethylene complexes: Spectroscopic and structural characterization

Adducts of the diphosphine cis-Ph₂P(CHCH)PPh₂ (L) with AgX (X = NO₃, BF₄, ClO₄ or CF₃SO₃) have been synthesized and characterized both in solution (¹H, ³¹P NMR) and in the solid state (IR, single crystal X-ray structure analysis). The topologies of the structures in the solid state were found to depend on the nature of the counter-ion X. The adduct AgNO₃:L (2:1)₂ is tetranuclear, derivative of the chair form, the bidentate ligands bridging peripheral silver centers, the nitrates being coordinated through two oxygen atoms, the first O,O′-bridging the second bridging bidentate.     

Physical,chemical and structural aspects of the electrode/solution interface

The structure of interfacial water at metal electrodes is inferred and discussed on the basis of the experimental evidence resulting from the use of such diverse techniques and approaches as thermodesorption spectra, electroreflection spectroscopy, dielectric studies, quantum-chemical calculations, work function measurements, electrochemical adsorption and kinetic investigations, heat of adsorption, potential of zero charge determination. The behaviour at metal surfaces is shown to parallel that at oxides since in both cases the same factors are basically involved. Qualitative and quantitative differences are pointed out for sp-, d- and sd-metals. Besides the more usual aspect of water preferential orientation, also the role played by the surface electrons of the metal is illustrated. Structural effects related to the atomic configuration of the surface are finally taken into consideration.     

Mono-, di- and tri-nuclear Ni(II) complexes of N-, O-donor ligands: structural diversity and reactivity

A series of mono-, di- and tri-nuclear Ni(II) complexes of N, O-donating molecules possessing H₂CNH and HCN moieties have been synthesized and characterized and the structures have been determined by single crystal X-ray diffraction. All these exhibited interesting molecular packing in their crystal lattices. Di-nuclear complexes were found to be cleaved in pyridine to result in mononuclear ones with additional coordinations being provided by pyridine. Di-nuclear complexes were found to form urea adducts as demonstrated based on absorption and vibrational studies.     

Synthesis,spectral and structural study of sulfur-containing copper(II) complexes

A series of four new copper(II) complexes [Cu(H₂L)(L¹)] 1, [Cu(H₂L)(PMDT)] 2, [Cu(H₂L)(Dien)] 3 and [Cu(H₂L)(L²)] 4 have been synthesized by template condensation (H₂L=thiodiglycolic acid, L¹=N-[(1)-1-(4-methylphenyl)ethylidene]benzohydrazide, PMDT=N,N,N′,N′,N ^′′-pentamethyldiethylene- triamine, Dien=diethylenetriamine L²=N-[(1)-pyridin-2-ylmethylidene]benzohydrazide). The bonding and stereochemistry of the complexes have been characterized by molar conductance, elemental analysis, magnetic susceptibility, infrared, UV–visible, electron paramagnetic resonance structural studies and electrochemical studies. g-Values were calculated for all complexes in polycrystalline form as well as in DMSO solution. The magnetic and spectral data indicate square pyramidal geometry for 1 and octahedral geometry for 2–4 complexes. Cyclic voltammograms for all the complexes are similar and involve two irreversible redox processes. Their biological properties have also been studied. The thio complexes show more antibacterial activity than the controlled one. The antibacterial activities of the compounds have also been tested against Escherichia coli with different concentrations.