Iron Coordination Compounds Research Articles

Synthesis, structure, and catalytic properties of iron complexes with mono- and bisformazans in sulfide oxidation and ethylene oligomerization reactions

Metal complexes with different numbers of iron atoms in a predominantly nitrogen-containing coordination environment have been synthesized on basis of benzothiazole mono- and bisformazans. The composition and structures of the resulting iron coordination compounds have been characterized by electronic absorption spectroscopy, elemental analysis, mass spectrometry, electron spin resonance, and magnetochemistry. The catalytic behavior of these metal chelates in the liquid-phase oxidation of sulfides and the oligomerization of ethylene has been studied.

Catalytic behaviour of a novel Fe(iii) Schiff base complex in the mild oxidation of cyclohexane

An iron coordination compound, possessing an unsaturated coordination environment, has been prepared by reaction of FeCl3with a polydentate Schiff base revealing a complex catalytic behaviour in the mild oxidation of cyclohexane by hydrogen peroxide.

Получение субстанции тимофера и ее количественное определение

Описано получение субстанции иммуномодулирующего препарата «Тимофер», представляющего собой водный 0,0148 % раствор координационных соединений изолейцил-триптофана и железа(II). Получают субстанцию механическим смешением порошков дипептида и сульфата железа(II) в эквимолярном соотношении. Препарат, полученный из разработанной субстанции, и препарат, приготовленный путем смешивания водных растворов дипептида и соли железа, не отличались друг от друга по физико-химическим показателям. Разработаны методы контроля качества субстанции тимофера по основным показателям. Применение разработанной субстанции позволило исключить стадии приготовления раствора дипептида, приготовления раствора соли железа и их смешивания при производстве готовой лекарственной формы препарата.

Разработка иммунотропного лекарственного препарата на основе координационных соединений синтетического низкомолекулярного тимусного пептида с ионом железа

Описана разработка иммуномодулирующего препарата тимофер, представляющего собой водный 0,0148 % раствор координационных соединений дипептида изолейцил-триптофан и сульфата железа (II), включая синтез свободного дипептида и лекарственной формы тимофера и технологию производства. Изучено взаимодействие и определен состав координационных соединений дипептида изолейцил-триптофан с ионом железа (II). Показано, что при взаимодействии пептида и иона металла в водном растворе образуется несколько комплексных форм, обусловленных ступенчатым процессом комплексообразования.

Syntheses and structural characterization of iron(II) and copper(II) coordination compounds with the neutral flexible bidentate N-donor ligands

Two new coordination compounds [Fe(bib)2(N3)2]n(1) and [Cu2(bpp)2(N3)4] (2) with azide and flexible ligands 1,4-bis(imidazolyl)butane (bib) and 1,3-bis(3,5-dimethylpyrazolyl)propane (bpp) were prepared and structurally characterized. In the 2D network structure of 1, the iron(II) ion lies on an inversion center and exhibits an FeN6 octahedral arrangement while in the dinuclear structure of 2, the copper(II) ion adopts an FeN5 distorted square pyramid geometry. In the complex 1, each μ2-bib acts as bridging ligand connecting two adjacent iron(II) ions while in the complex 2, the bpp ligand is coordinated to copper(II) ion in a cyclic-bidentate fashion forming an eight-membered metallocyclic ring. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction. Thermal analysis of polymer 1 was also studied.

Synthesis, crystal structure, and physicochemical properties of the new metal-organic framework — the iron(iii) complex with benzene-1,3,5-tricarboxylate

A new iron(iii) coordination compound with the benzene-1,3,5-tricarboxylate anion of the composition [Fe iii 2(OH)0.3(H2O)1.7(btc)4/3]Cl1.7·2.8DMF·1.9H2O (1) was synthesized. Its crystal structure was determined, and the Mossbauer spectra were analyzed. The adsorption of salicylaldehyde and nitromethane by compound 1 was studied. The adsorption kinetics of salicylaldehyde is described by the pseudo-second order equation. The diffusion of this aldehyde in particles of compound 1 is, most probably, the rate-limiting step in the Henry reaction.

Spin-crossover in complexes of iron(II) carboranes with tris(pyrazol-1-yl)methane

Synthesis procedures for coordination compounds of iron(II) 1,5,6,10-tetra(R)-7,8-dicarba-nido-undecaborates(-1) (carboranes) with tris(pyrazol-1-yl)methane (HC(pz)3) of the composition [Fe{HC(pz)3}2]A2·nH2O (A = (7,8-C2B9H12)− (I), (1,5,6,10-Br4-7,8-C2B9H8)− (II), (1,5,6,10-I4-7,8-C2B9H8)− (III), n = 0–2) are developed. The compounds are studied by static magnetic susceptibility in the temperature range of 160–500 K, electron (diffuse reflectance spectra), IR, and Mossbauer spectroscopy methods. It is shown that the complexes have high-temperature spin-crossover 1A1 ⇔ 5T2. Transition temperatures (Tc) for I–III are 370 K, 380 K, and 400 K respectively. Spin-crossover is accompanied by thermochromism (color change: pink ⇔ white).

Synthesis and Structural Characterization of Molybdenum(VI) and Iron(II) Coordination Compounds with S-Alkyl-N-methyl-S-(2-pyridyl)sulfoximines and Catalytic Epoxidation Activity of the Molybdenum Complexes

Coordination compounds oxido(diperoxido)(S-butyl-N-methyl-S-(2-pyridyl)sulfoximine)molybdenum(VI), [MoO(O2)2{SO(NMe)(n)Bu(NC5H4)}] (5c), and bis{(dichlorido)(N,S-dimethyl-2-pyridylsulfoximine)iron(II)}, tetrahydrofuran solvate (1:1) (6), [FeCl2{SO(NMe)Me(NC5H4)}]2·THF are prepared from the free ligand 4 and molybdenum(VI) oxidediperoxide(dihydrate) and iron dichloride, respectively. The crystal structures reveal a trigonal bipyramid with the pyridine ring and the single oxygen on molybdenum in a trans arrangement for 5c and a planar μ(2)-Cl2Fe2 ring with trans-oriented exocyclic Cl atoms for 6 whereas the structures of the N,N-dicoordinated ligands are only little effected by the metals. Coordination compounds (5) efficiently catalyze the epoxidation of cyclooctene or of monosubstituted alkenes by tert-butyl hydroperoxide.

Investigating the effect of flexible ligands on the crystal engineering of the iron(II) coordination compounds

Iron(II) coordination compounds [Fe(bib)2(NCS)2]n(1) and [Fe(bpp)(NCS)2] (2) were synthesized by using the neutral flexible bidentate N-donor ligands 1,4-bis(imidazolyl)butane (bib) and 1,3-bis(3,5-dimethylpyrazolyl)propane (bpp), mono-anionic NCS− ligand and appropriate iron(II) salts. In the CdSO4 network structure of 1, the iron(II) ion lies on an inversion center and exhibits an FeN6 octahedral arrangement while, in the monomeric structure of 2, the iron(II) ion adopts an FeN4 tetrahedral geometry. In the complex 1, each μ2-bib acts as bridging ligand connecting two adjacent iron(II) ions while in the complex 2, the bpp ligand is coordinated to an iron(II) ion in a cyclic-bidentate fashion forming an eight-membered metallocyclic ring. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction. Thermal analysis of polymer 1 was also studied. An attempt to synthesize [Fe(bbd)(NCS)2] (3) (bbd=1,4-bis(3,5-dimethylpyrazolyl)butane) with the reaction of bbd, Fe(NH4)2(SO4)2·6H2O and KNCS was failed.

Iron complexes with gallic acid: a computational study on coordination compounds of interest for the preservation of cultural heritage

The electronic structures of iron coordination compounds [FeL4H12]−, [FeL4H12]2−, [Fe3L8H22]−, and [Fe3L8H22]2− (H4L = gallic acid, 3,4,5-trihydroxybenzoic acid) have been studied by density functional theory calculations, together with the 1-D periodic complex [Fe3L6H15]∞. Data regarding the ground-state spin multiplicities of these models for iron gall inks, the charge and spin distributions, the oxidation states of the metal centers, and the oxidizing potentials of the complexes have been computed. The absorption properties of these compounds have been related to the electronic structure of the coordinated ligands.

Spin state switching in iron coordination compounds.

The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices.The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property.

Spin Crossover and Thermochromism of Iron(II) Coordination Compounds with 1,2,4‐Triazoles and Tris(pyrazol‐1‐yl)methanes

AbstractWe review herein the synthesis and investigation of iron(II) coordination compounds with 1,2,4‐triazoles or tris(pyrazol‐1‐yl)methanes as ligands. Both groups of complexes demonstrate thermally induced spin crossover accompanied by thermochromism [pink (magenta) ↔ white color change]. Factors that influence the nature and temperature of the spin crossover are discussed.

Synthesis and characterization of poly(siloxane–azomethine) iron(III) coordination compounds

Siloxane-containing polyazomethines with linear (PAZ) and cross-linked (CPAZ) architectures and their iron complexes (FePAZ and CFePAZ) have been prepared. The structures of the resulted compounds were investigated by spectral methods (FT-IR, 1H NMR, UV–vis) and electrospray ionization mass spectrometry (ESI-MS). X-ray fluorescence spectrometry was used to determine the Si/Fe ratio and for quantitative analysis of silicon. Paramagnetic susceptibility (χ) and magnetic moment (μ eff) of the soluble iron complex were estimated based on 1H NMR measurements. The iron spin state was determined by Mössbauer spectroscopy, while the electrochemical behavior was studied by cyclic voltammetry. The catalytic activity in hydrogen peroxide decomposition reaction, in alkaline solution was tested. The compound FePAZ proved to increase the dielectric constant of a silicone matrix in which it was incorporated even in very low percent, acting also as an effective plasticizer.

Spin crossover in the coordination compounds of iron(II) with tris(3,5-dimethylpyrazol-1-yl)methane

Iron(II) complexes with tris(3,5-dimethylpyrazol-1-yl)methane {HC(3,5-Me2Pz)3} of the composition [Fe{HC(3,5-Me2Pz)3}2]Am · nH2O (A = Cl− (I), ClO 4 − (II), SO 4 2− (III), CF3SO 3 − (IV), m = 1, 2, n = 0.1) are synthesized. The compounds are studied by static magnetic susceptibility, IR and diffuse reflectance spectroscopy, and X-ray structure analysis. The crystal structures of two polymorphous modifications of the [Fe{HC(3,5-Me2Pz)3}2](ClO4)2 (IIa and IIb) and [Fe{HC(3,5-Me2Pz)3}2](CF3SO3)2 (IV) complexes are determined. The temperature dependence μeff(T) shows that the spin crossover 1 A 1 ai 5 T 2 is observed in the polycrystalline phase of complex I and in one of the single-crystal phases of complex II (IIa) and is accompanied by thermochromism (the change of the dark pink color ai to white).

Synthesis of a water purification reagent based on the Fe(II), Fe(III), Al(III), Cl−-H2O-OH-system

Formation kinetics of a water purification reagent based on the Fe(II), Fe(III), Al(III), Cl−-H2O-OH− system was studied in relation to the nature and state of the surface of dispersed aluminum, initial concentration of iron(III) ions, and pH value. The chemical composition of heteronuclear coordination compounds of iron and aluminum was determined by potentiometry, nuclear magnetic resonance, and X-ray phase analysis.

Synthesis, characterization, spectroscopic, crystal structures and solution studies of two coordination compounds of zinc(II) and iron(III) based on chelidamic acid and acridine

Two new proton transfer compounds, (acrH)2[Zn(hypydc)2]·10H2O 1 and (acrH)[Fe(hypydc)2]·4.5H2O 2 [where hypydcH2=4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) and acr=acridine] have been synthesized and characterized by elemental analysis, spectral (UV–Vis, IR), 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffraction. The crystallographic analysis revealed that ZnII and FeIII atoms are coordinated by two N atoms and four O atoms from the carboxylate groups of (hypydc)2− ligands, forming a distorted octahedral geometry. In the anions two pyridine rings are inclined to one another by 88.10(5)° and 83.95(13)° for 1 and 2, respectively. The (H2O)n [n=3–6] cyclic–linear water clusters connected two layers of anionic complexes in 1. The crystal packing of 1 show a 3D network formed through H-bonds involving water molecules, NH groups of acridinium and carboxylate anions. In 2 two types of rubout O–H⋯O hydrogen bond synthons, R44 (16) and R44 (18) link the anions and water molecules to form two-dimensional network parallel to bc plane. In crystal structures of both complexes extensive O–H⋯O, N–H⋯O and C–H⋯O hydrogen bonds as well as electrostatic forces, C–O⋯π and π–π stacking play important roles in stabilizing structures. The protonation constants of hypydc and acr, in all of probability protonated forms, the equilibrium constants for the hypydc–acr proton transfer system and the stoichiometry and stability of complexation of this system with Zn2+ and Fe3+ ions in 50% dioxane–50% water (V/V) solvent were investigated by potentiometric pH titration method. The stoichiometries of the most complex species in solution were compared with corresponding crystalline metal ion complexes 1 and 2.

Synthesis and Characterization of New Pentacoordinate Iron‐Based Aryloxide Complexes

AbstractHeterobimetallic lithium–iron coordination compounds are interesting targets for several reasons: they can be used as precursors for mixed metal oxides, as catalysts, for example, for ring‐opening polymerization reactions or to study oxidation/reduction processes. Finally their magnetic properties are also of interest. New heterobimetallic aryloxide complexes, namely [(thf)4Li3Fe(OPh)3(O2C6H4)Cl]2 (1), [{(thf)3Li3Fe(OPh)5Cl}3]n (2), and [(thf)3Li3Fe(OPh)6]2 (3), have been synthesized and characterized by single‐crystal X‐ray diffraction. While compounds 1 and 3 were synthesized by an oxidative substitution reaction, compound 2 was directly obtained from the FeIII salt. These compounds are accessible by both synthetic pathways. Additionally, in compound 1, the phenoxy ligand was catalytically oxidized to ortho‐catechol, which was incorporated into the structure of 1 as a ligand that coordinates strongly to iron. All compounds feature the FeIII ion with a trigonal, bipyramidal environment, with coordination number 5.

High-temperature spin crossover in the [Fe(L) 2][Fe(L)(NCS) 3](NCS)·2H 2O complex, L = tris(pyrazol-1-yl)methane

A novel iron(II) coordination compound with tris(pyrazol-1-yl)methane ( L) of the composition [FeL 2][Fe(L)(NCS) 3](NCS)·2H 2O has been synthesized. Employing the XRD technique, its crystal structure has been determined. The compound was studied with the help of IR and UV–Vis spectroscopy and static magnetic susceptibility methods. A magnetochemical study of the complex within the temperature range 78–400 K has demonstrated that the compound exhibits a high-temperature spin crossover (SCO) 1А 1 ⇔ 5Т 2. The transition temperature amounts to 380 K.

High-temperature spin transition in the iron(II) trifluoromethylsulfonate, perrhenate, and tetraphenylborate complexes with tris(pyrazol-1-yl)methane

New coordination compounds of iron(II) trifluoromethylsulfonate, perrhenate, and tetraphenylborate with tris(pyrazol-1-yl)methane (HC(Pz)3) of the composition [Fe(HC(Pz)3)2]A2 (A = CF3SO3− (I), ReO4− (II), and B(C6H5)4− (III)) were synthesized and studied by the method of static magnetic susceptibility and IR and electronic spectroscopies. The crystal and molecular structures of compounds I and II were determined by X-ray diffraction analysis. The magnetochemical study of complexes I—III in the interval from 275 to 500 K showed that they possessed the high-temperature spin transition 1A1 ⇄ 5T2 accompanied by thermochromism.

ChemInform Abstract: Isomers in the Chemistry of Iron Coordination Compounds

AbstractReview: 111 refs.