Mixed Ligand Complexes Of Iron Research Articles

Dual magnetic behavior of Co(II) and Fe(II) bis(chelate) adducts with Di-o-diiminobenzoquinone: Quantum chemical modeling

Computational modeling (DFT UB3LYP*/6-311++G(d,p)) of electroneutral binuclear 2: 1 adducts of cobalt and iron bis(chelates) with N-phenyl-di-o-diiminobenzoquinone bearing the dimethylene linker is performed. The geometries of all electromers of the complexes are determined, and their stabilization energies and exchange interaction parameters are calculated. The magnetic properties of the compounds under study are determined by the metal nature: the cobalt diketonate adducts undergo one- and two-step valence tautomeric rearrangements, while the mixed-ligand iron complexes are capable of demonstrating spin crossover. The calculation results make it possible to regard the studied adducts as the basis for designing molecular switches and spin qubits.

Computational design of magnetically active trinuclear heterometallic complexes on the basis of 1,3,5-triazapentadiene ligands

A series of trinuclear mixed-ligand complexes of iron(II) 2,6-di(pyrazol-1-yl)pyridine moieties with linkers on the basis of 1,3,5-triazapentadiene transition metal (M = Co, Ni, Cu, Zn) bischelates has computationally been designed using the density functional theory TPSSh/6-311++G(d,p) calculations. The systems possessing complete (M = Co, Ni) and partial (M = Cu, Zn) two-step spin-crossover phenomenon at ferrous ions have been revealed. Two spin-state switching mechanisms determining by spin-crossover at iron centers and configurational isomerism at cobalt ion may simultaneously occur in solution of corresponding heterometallic compound (M = Co). The nature of the exchange interactions between paramagnetic metal centers is controlled by variation of a metal in bischelate linker (M = Co, Ni, Cu, Zn). Energy and magnetic characteristics of electromeric forms of the complexes with nickel and copper central metal ions (M = Co, Ni) allow to consider them as promising candidates for the design of molecular switches.

Studies on mixed ligand complexes of iron (III) with dibasic tridentate schiff bases as primary and naphthoic acids as Co-Ligands

Studies on mixed ligand complexes of iron (III) with dibasic tridentate schiff bases as primary and naphthoic acids as Co-Ligands

Introducing a new azoaromatic pincer ligand. Isolation and characterization of redox events in its ferrous complexes.

The isolation and complete characterization of a new bis-azoaromatic ligand, 2,6-bis(phenylazo)pyridine (L), are described, and its coordination to iron(II) is reported. A pseudo-trigonal-bipyramidal mixed-ligand complex of iron(II), FeLCl2 (1), and a homoleptic octahedral iron complex, mer-[Fe(L)2]ClO4 [2]ClO4, have been synthesized from L and FeCl2 or hydrated Fe(ClO4)2, respectively, in boiling methanol. Determination of the X-ray crystallographic structure together with magnetic data (≈ 5.06 μB) and Mössbauer analysis of 1 established a high-spin Fe(II) complex ligated by one neutral 2,6-bis(phenylazo)pyridine ligand. The X-ray crystallographic structure (showing dN-N > 1.30 Å), Mössbauer data, and magnetic susceptibility measurements (≈ 1.65 μB) as well as a nearly isotropic EPR signal with only a small metal contribution at g = 1.968, on the other hand, suggest a low-spin Fe(II) complex with a one-electron-reduced radical ligand coordination in [2]ClO4. The ligand and the metal complexes have well-behaved redox properties, with the ligand(s) functioning as the redox-active site(s) responsible for redox events. The uncoordinated ligand, L, displays a reversible one-electron wave at -1.07 V and a quasi-reversible wave at -1.39 V. The partially reduced ligand L(•-) shows a single-line EPR spectrum at g = 2.001, signifying that L(•-) is a free radical. While complex 1 shows a reversible reduction at -0.08 V and an irreversible cathodic response at -0.98 V, the bis-chelate [2]ClO4 undergoes a reversible one-electron oxidation at 0.54 V and three successive reversible one-electron reductions at -0.18, -0.88, and -1.2 V, all occurring at the ligands without affecting the metal ion oxidation state. The electronic structures of the parent monocationic complex [2](+) and its oxidized and reduced forms, generated by exhaustive electrolyses, have been characterized by using a host of spectroscopic techniques and density functional theory (DFT). It is found that the 2,6-bis(phenylazo)pyridine ligand (L) is truly redox noninnocent and is capable of coordinating transition-metal centers in its neutral ([L](0)), monoanionic monoradical ([L(•)](-)), and dianionic diradical ([L(••)](2-)) forms.

Synthesis, physicochemical characterization and biological activity of nano complexes of iron(III) of 3(2'‐hydroxyphenyl)‐5‐(4′‐substituted phenyl) pyrazolines and aspartic acid

Mixed ligand complexes of Iron(III) with aspartic acid and 3(2′‐hydroxy phenyl)‐5‐(4′‐substituted phenyl) pyrazolines of type [Fe(C4O4NH6)2(C15H12N2OX)] and [Fe(C4O4NH6)(C15H12N2OX)2], where (C4O4NH6) = aspartate, (C15H12N2OX) = deprotonated 3(2′‐hydroxyphenyl)‐5‐(4′‐substituted phenyl) pyrazolines (X = H, CH3, OCH3, Cl), have been synthesized. These newly synthesized derivatives have been physicochemically characterized by elemental analysis (C, H, N, Cl and Fe), magnetic moment data, thermogravimetric analysis, molar conductance, cyclic voltammetry, spectral analysis (UV–visible, IR, far IR and fast atom bombardment mass spectrometry). Scanning electron microscopy, transmission electron microscopy and X‐ray powder diffraction studies have been carried out for powdered samples, which show nanometric particles of these derivatives. Antibacterial and antifungal potential of free pyrazoline and some iron(III) complexes have been evaluated. Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis, spectroscopic (IR, electronic, FAB-mass, and PXRD), magnetic, and antimicrobial studies of new iron(III) complexes containing Schiff bases and substituted benzoxazole ligands

Mixed ligand complexes of iron(III), [Fe(sb)2(py)Cl] · 2H2O (1–9) [where sbH = Schiff bases (derived from condensation of 2-aminopyridine (sapH), 2-aminophenol (saphH), o-toluidine (o-smabH), aminobenzene (sabH), p-toluidine (p-smabH), 3-nitroaniline (snabH), and anthranilic acid (saaH) with salicylaldehyde and substituted (mercapto-)benzimidazole (mbzH), {2-(o-hydroxyphenyl)}benzoxazole, (pboxH)], have been synthesized by the interactions of iron(III) chloride with corresponding ligands in 1 : 2 molar ratio in refluxing pyridine. These complexes have been characterized by elemental analyses, melting points, spectral, and magnetic studies. Powder X-ray diffraction studies of some representative complexes are also reported herein. The antibacterial and antifungal activities of the free ligands and their iron(III) complexes were found in vitro. The complexes showed good antibacterial and antifungal effect to some bacteria and fungi. Two standard antibiotics (chloromphenicol and terbinafine) were used for comparison with these complexes.

Mixed-ligand complexes of iron(II), iron(III), copper(II), and cobalt(II) with pyrazolonic and 2,2′-bipyridine ligands

New mixed-ligand complexes, [M2(BAMP)(bipy)2][MCl4]2, M=Co+2(1), Cu+2(2), [M2(TAMEN)(bipy)2][MCl4]2, M=Fe+2(3), Co2+(4), and [Fe2(TAMEN)(bipy)2][FeCl6]2 (5), where BAMP and TAMEN stand for the Mannich bases N,N′-bis(antipyryl-4-methylene)-piperazine and N,N′-tetra(antipyryl-4-methylene)-1,2-ethane-diamine, respectively, have been obtained and characterized by elemental analyses, conductometric and magnetic susceptibility measurements at room temperature, mass spectrometry, UV-Vis, infrared, and mass spectroscopy, and 1H NMR spectra for the ligands.

Synthesis, X-ray structure and study of a mixed ligand iron(III) complex with tridentate Schiff base as a homogeneous catalyst in the efficient oxidation of sulfides

Abstract A mononuclear mixed ligand complex of iron, [FeIII(N-OPh-sal)(acac)EtOH], where Hacac and N-HOPh-Hsal denote acetylacetone and N-hydroxyphenyl-salicylideneamine, respectively, has been synthesized and characterized by elemental analysis, spectral studies and X-ray crystallography. The catalytic system containing this complex and urea hydrogen peroxide as oxidizing agent was used to selectively oxidize a range of sulfides to the corresponding sulfoxides in good yields under mild conditions. The electronic spectra of the catalytic system were applied to explore reactivity and stability of the catalyst during sulfide oxidation reactions and to examine the nature of active species, as well.

ESI‐MS studies of mixed‐ligand Fe(II) complexes containing 1,10‐phenanthroline and 1,10‐phenanthroline‐5,6‐dione as ligands

In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione. Owing to the solvent-ligand hydrogen-bond formation, the solvent-ligand clusters were formed in the polar protic solvents. The number of protic solvent molecules per complex ion in cluster depended on the number of 1,10-phenanthroline-5,6-dione ligands in the complex ion. Unlike MeOH, EtOH, or water, ACN was not involved in the formation of the solvent clusters with the iron complexes containing 1,10-phenanthroline-5,6-dione as ligand. We also showed that the NCS- group under certain solvent conditions served as a bidentate ligand.

Mixed ligand complexes of iron-, cobalt- and nickel(II) with 2,3-dihydroxypyridine and some nitrogen donors

Mixed ligand complexes of iron-, cobalt- and nickel(II) with 2,3-dihydroxypyridine and some nitrogen donors

Synthesis, Spectral Studies, Spin Cross-Over in Mixed Ligand Complexes of Iron(II) and the Influence of Solvent on Magnetic Behaviour

Mixed ligand complexes of iron(II) with polypyridine ligands like 1, 10-phenanthroline (phen), 2,2′-bipyridine (bpy) and oxalic acid (ox) have been synthesized, viz. [Fe (phen)2ox]. 5. 2H2O and [Fe(bpy)l. 04(ox)1. 1]. 0. 3H2O and were characterized by analytical, spectral, magnetic and thermal studies. Variable temperature magcetic measurements indicate spin cross-over changes of the Fe(II) complexes with temperature. Mossbauer studies confirm the predominantly low-spin nature of the complexes at low temperature while the X-ray photoelectron spectrum (XPS) of the bpy complex shows divalency of the metal center. The minor variations in the crystal packing due to the change in the method of preparation and the number of water molecules present in the crystal lattice drastically change the magnetic behaviour of these systems when compared with those of analogous complexes reported earlier.

Mixed-ligand Complexes of Iron-, Cobalt- and Nickel(II) with 2-Amino-3- hydroxypyridine and Some Nitrogen Donors

Mixed-ligand Complexes of Iron-, Cobalt- and Nickel(II) with 2-Amino-3- hydroxypyridine and Some Nitrogen Donors

Chemistry of Iron with Dipicolinic Acid. 4. Mixed-Ligand Complexes of Iron(III) and Related Compounds

Chemistry of Iron with Dipicolinic Acid. 4. Mixed-Ligand Complexes of Iron(III) and Related Compounds

Complexes of Iron(III) Containing Heterocyclic Ligands

Abstract The following mixed ligand complexes of iron(III) have been synthesised and characterised: Fe(Pipdtc)2.,(HDz); Fe(Pipdtc)(OX)2, Fe(Pipzdtc)(OX)2, Fe(morphdtc)(OX)2, Fe(Etxan)(OX)2, Fe(i-Prxan)(OX)2, Fe(Buxan)(OX)2, and Fe(i-Amxan)(OX)2. The spectral data permited us to assign an octahedral structure around iron(III). The thermal decomposition of the complexes has been studied and the decomposition steps have been correlated with the proper evolved or decomposed products.

Mixed ligand complexes of iron with cyanide and phenanthroline as new probes of metalloprotein electron transfer reactivity. Analysis of reactions involving rusticyanin from Thiobacillus ferrooxidans.

A family of 12 different mixed ligand complexes of iron with cyanide and substituted 1,10-phenanthroline was prepared. The electron transfer properties of each reagent were systematically manipulated by varying the substituent(s) on the aromatic ring system and the stoichiometry of the two types of ligands in the complex. Values for the standard reduction potentials of each member of this family of electron transfer reagents were determined and spanned from 500 to 900 mV. The one-electron transfer reactions between each of these substitution-inert reagents and the high potential blue copper protein, rusticyanin, from Thiobacillus ferrooxidans were studied by stopped flow spectrophotometry under acidic conditions. For comparison with the protein results, the kinetics of electron transfer between each of these reagents and sulfatoiron were also investigated. The Marcus theory of electron transfer was successfully applied to this set of kinetic data to demonstrate that 10 of the 12 reagents had equal kinetic access to the redox center of the rusticyanin and utilized the same reaction pathway for electron transfer. The utility of these synthetic electron transfer reagents in characterizing the electron transfer properties of very high potential, redox-active metalloproteins is illustrated.

Unusually stable monothiolate and S/N, S/O mixed ligand complexes of iron(III) tetramesitylporphyrin

The reaction of tetramesitylporphinatoiron(III) hydroxide with ethyl 3-mercaptopropionate in toluene generates the air and temperature stable five co-ordinate iron(III) monothiolate complex, which adds imidazole or other Lewis base to give a six co-ordinate adduct, the unusual stability of which allows characterization by UV-VIS spectrophotometry at room temperature.

Spherical wave analysis of EXAFS data including multiple scattering

A rapid method for spherical-wave calculation of EXAFS spectra including multiple scattering is described. Examples include Co and Cu imidazole complexes, a mixed ligand iron complex, and the native and substrate complexed forms of protocatechuate 3,4-dioxygenase (PCD).

Experimental approach to the chemical evolution of iron containing enzymes: Role of mixed ligand complexes of iron(II)

Experimental approach to the chemical evolution of iron containing enzymes: Role of mixed ligand complexes of iron(II)

Chemical evolution of iron containing enzymes: mixed ligand complexes of iron as intermediary steps.

Activities of the iron complexes of evolutionary importance like K4[Fe(CN)6], K4[Fe(CN)5(gly)], and K4[Fe(CN)5(trigly)] have been tested towards some redox reactions of biological significance, namely, decomposition of hydrogen peroxide, dehydrogenation of NADH and ascorbic acid both coupled with reduction of methylene blue. It has been observed that the catalytic activities of iron (II) complexes towards the redox reactions studied at pH 9.18 followed the order, K4[Fe(CN)6] less than K4[Fe(CN)5(gly)] less than K4[Fe(CN)5(trigly)]. Decomposition of H2O2 catalysed by cyanocomplexes of iron (II) has been discussed through the formation of an innersphere complex in which loosly bound ligands like, glycine and triglycine are replaced by hydroperoxide ion. A tentative mechanism for the catalysed decomposition of H2O2 has been discussed. Based upon the experimental observations a hypothesis on the evolution of iron containing enzymes has been envisaged as: iron(II) ion----iron(II) cyanide complexes----mixed ligand iron(II) cyanide and amino acid complexes----iron(II) complexes of macromolecules----pŕoenzyme or early enzyme containing iron(II).

Synthesis and Study of Mixed Ligand Complexes of Iron(III) with Fluorinated 1,3-Diketones

Abstract Mixed ligand complexes of iron(III) with bis(salicylidene)ethylenediimine, a tetradentate Schiff base, and various fluorinated 1,3-diketones have been prepared. These high-spin complexes with an octahedral geometry have been characterised on the basis of elemental analyses, spectral data and magnetic studies.