The effect of copper(II), iron(II) sulphate and vitamin C combinations on the weak antimicrobial activity of (+)-catechin against Staphylococcus aureus and other microbes

Few attempts have been made to improve the activity of plant compounds with low antimicrobial efficacy. (+)-Catechin, a weak antimicrobial tea flavanol, was combined with putative adjuncts and tested against different species of bacteria. Copper(II) sulphate enhanced (+)-catechin activity against Pseudomonas aeruginosa but not Staphylococcus aureus, Proteus mirabilis or Escherichia coli. Attempts to raise the activity of (+)-catechin against two unresponsive species, S. aureus and E. coli, with iron(II) sulphate, iron(III) chloride, and vitamin C, showed that iron(II) enhanced (+)-catechin against S. aureus, but not E. coli; neither iron(III) nor combined iron(II) and copper(II), enhanced (+)-catechin activity against either species. Vitamin C enhanced copper(II) containing combinations against both species in the absence of iron(II). Catalase or EDTA added to active samples removed viability effects suggesting that active mixtures had produced H2O2via the action of added metal(II) ions. H2O2 generation by (+)-catechin plus copper(II) mixtures and copper(II) alone could account for the principal effect of bacterial growth inhibition following 30 minute exposures as well as the antimicrobial effect of (+)-catechin–iron(II) against S. aureus. These novel findings about a weak antimicrobial flavanol contrast with previous knowledge of more active flavanols with transition metal combinations. Weak antimicrobial compounds like (+)-catechin within enhancement mixtures may therefore be used as efficacious agents. (+)-Catechin may provide a means of lowering copper(II) or iron(II) contents in certain crop protection and other products.

Synthesis, characterisation and magnetic properties of a one-dimensional Iron(II) coordination polymer

A new iron(II) coordination polymer, [FeCl2(NC7H9)2(N2C12H12)], has been synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. This material crystallizes in the monoclinic space group C2/c, with a = 11.2850(6), b = 13.8925(7), c = 17.0988(9) Å and β = 94.300(3)º (Z = 4). The crystal structure consists of neutral zig-zag chains, in which the iron(II) ions are octahedrally coordinated. The infinite polymer chains are packed into a three-dimensional structure through C–H···Cl interactions. Magnetic susceptibility measurements reveal the existence of weak antiferromagnetic interactions between the iron(II) ions. The effective magnetic moment, μ eff = 5.33 μ B , is consistent with a high-spin iron(II) configuration.

Solvatochromic and lonochromic Effects of Iron(II)bis-(1,10-phenanthroline)dicyano: a Theoretical Study

Solvatochromic and ionochromic effects of the iron(II)bis(1,10-phenanthroline)dicyano (Fe(phen)(2)(CN)(2)) complex were investigated by means of combined DFT/TDDFT calculations using the PBE and B3LYP functionals. Extended solvation models of Fe(phen)(2)(CN)(2) in acetonitrile and aqueous solution, as well as including interaction with Mg(2+), were constructed. The calculated vertical excitation energies reproduce well the observed solvatochromism in acetonitrile and aqueous solutions, the ionochromism in acetonitrile in the presence of Mg(2+), and the absence of ionochromic effect in aqueous solution. The vertical excitation energies and the nature of the transitions were reliably predicted after inclusion of geometry relaxation upon aqueous micro- and global solvation and solvent polarization effect in the TDDFT calculations. The two intense UV-vis absorption bands occurring for all systems studied are interpreted as transitions from a hybrid Fe(II)(d)/cyano N(p) orbital to a phenanthroline pi* orbital rather than a pure metal-to-ligand-charge transfer (MLCT). The solvatochromic and ionochromic blue band shifts of Fe(phen)(2)(CN)(2) were explained with preferential stabilization of the highest occupied Fe(II)(d)/cyano N(p) orbitals as a result of specific interactions with water solvent molecules or Mg(2+) ions in solution. Such interactions occur through the CN(-) groups in the complex, and they have a decisive role for the observed blue shifts of UV-vis absorption bands.

Spectroscopic and electrochemical properties of iron(II) complexes of polydentate Schiff bases containing pyrazine, pyridine and imidazole groups

We report the synthesis and spectroscopic/electrochemical properties of iron(II) complexes of polydentate Schiff bases generated from 2-acetylpyridine and 1,3-diaminopropane, acetylpyrazine and 1,3-diaminopropane, and from 2-acetylpyridine and L-histidine. The complexes exhibit bis(diimine)iron(II) chromophores in association with pyrazine, pyridine or imidazole groups displaying contrasting pi-acceptor properties. In spite of their open geometry, their properties are much closer to those of macrocyclic tetraimineiron(II) complexes. An electrochemical/spectroscopic correlation between E degrees(Fe(III/II)) and the energies of the lowest MLCT band has been observed, reflecting the stabilization of the HOMO levels as a consequence of the increasing backbonding effects in the series of compounds. Mossbauer data have also confirmed the similarities in their electronic structure, as deduced from the spectroscopic and theoretical data. (C) 2008 Elsevier B.V. All rights reserved.

Effect of Iron II on Hydroxyapatite Dissolution and Precipitation in vitro

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Iron(II) djenkolate: synthesis and properties

Djenkolate complex of iron, [Fe(C(7)H(12)N(2)O(4)S(2))]. H(2)O, has been synthesized by the reaction of potassium djenkolate with Fe(SO(4)). 7H(2)O under nitrogen atmosphere. X-Ray diffraction pattern has been indexed in orthorhombic system with lattice parameters: a=11.24 Angstrom, b=7.50 Angstrom and c=6.96 Angstrom. According to IR spectroscopy, coordination is performed through COO(-) and NH(2) groups. An octahedral geometry for Fe ion is suggested by UV-Vis and Mossbauer spectroscopies. Thermal decomposition leads to the formation of Fe(2)O(3) (hematite). The compound shows poor solubility in water and in common organic solvents. (C) 2000 Elsevier B.V. S.A. All rights reserved.

Synthesis, characterization and electropolymerization of a new polypyrrole iron(II) Schiff-base complex

This work presents the synthesis of the complex [Fe(L)(2)](PF6)(2) (.) H2O (L = 2,6-bis[1-(3-pyrrol-1-yl-propylimino)ethyl]pyridine (Fig. 1) and its characterization through elemental and thermal analysis, X-ray diffraction and UV-Vis, IR and H-1 NMR spectra. The use of this compound in the preparation of modified electrodes is also described. The best electrochemical parameters to achieve optimum film formation have been established and the effects of both the upper-limit of the applied scanning potential (E-aul) and the number of scans on the efficiency of film formation have been investigated. Film surface morphology has been characterized by atomic force microscopy. (C) 2004 Elsevier Ltd. All rights reserved.

Reaction of pentacarbonyliron with a nitrogen heterocycle. X-ray crystal structure of bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II)

The monomeric compound bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II) was synthesized and studied by IR and Mossbauer spectroscopy, cyclic voltammetry and X-ray diffraction. The molecule has two terminal carbonyl groups and two quinoline-2-thiolate anions coordinated as N,S-donor chelates, and the iron atom shows an octahedral coordination geometry.

Spin-crossover in metallomesogens of iron(II)

Covalent grafting mesogenic groups to the coordination cores of the parent mononuclear low-spin and spin-crossover compounds afforded metallomesogenic complexes of iron(II). In comparison with the parent complexes the spin-crossover properties of the alkylated derivatives are substantially modified. The type of the modification was found to be dependent on the properties of the parent system and the nature of the used anion, however, the general tendency is the destabilization of the low-spin state at the favor of spin-crossover or high-spin behavior below 400 K. The structural insight revealed the micro-segregated layered organization. The effect of the alkylation of the parent compounds consists first of all in the change of the lattice to a two-dimensional lamellar one retaining significant intermolecular contacts only within the ionic bilayers. The comprehensive analysis of the structural and thermodynamic data in the homologous series pointed at the mechanism of the interplay between the structural modification on melting and the induced anomalous change of the magnetic properties. A family of one-dimensional spin-crossover polymers was synthesized and characterized using a series of spectroscopic methods, X-ray powder diffraction, magnetic susceptibility measurements and differential scanning calorimetry. The copper analogue of was also synthesized and its crystal structure solved. In comparison with the mononuclear systems, the polymeric mesogens of iron(II) are less sensitive to the glass transition, which was attributed to the moderate concomitant variation of the structure. Nevertheless, the observed increase of the magnetic hysteresis with lengthening of the alkyl substituents was ascribed to the interplay of the structural reorganization of the coordination core due to spin-crossover with the structural delay in the spatial reorganization of the mesogenic substituents. The classification of mononuclear and polymeric metallomesogens according to the interactions between the structural- and the spin-transition and analysis of the data on the reported spin-crossover metallomesogens led to the separation of three types, namely: Type i: systems with coupling between the electronic structure of the iron(II) ions and the mesomorphic behavior of the substance; Type ii: systems where both transitions coexist in the same temperature region but are not coupled due to competition with the dehydration or due to negligible structural transformation; Type iii: systems where both transitions occur in different temperature regions and therefore are uncoupled. Fine-tuning, in particular regarding the temperature at which the spin-transition occurs with hysteresis properties responsible for the memory effect, are still a major challenge towards practical implementation of spin-crossover materials. A possible answer to the problem could be materials in which the spin-crossover transition is coupled with another transition easily controllable by external stimuli. In the present thesis we have shown the viability of the approach realized in the mesogenic systems with coupled phase- and spin-transitions.

A Donor-Acceptor Tetrathiafulvalene Ligand Complexed to Iron(II): Synthesis, Electrochemistry, and Spectroscopy of Fe(phen)(2)(TTF-dppz)(PF6)(2)

The synthesis and photophysical properties of the complex Fe(phen)(2)(TTF-dppz)(2+) (TTF-dppz = 4',5'-bis-(propylthio)tetrathiafulvenylidipyrido3,2-a:2',3'-c-phenazine, phen = 1,10-phenanthroline) are described. In this complex, excitation into the metal ligand charge transfer bands results in the population of a high-spin state of iron(II), with a decay lifetime of approximately 1.5 ns, in dichloromethane, at room temperature. An intraligand charge transfer state can also be obtained and has a lifetime of 38 ps. A mechanism for the different states reached is proposed based on transient absorption spectroscopy.