FeIII Ions Research Articles

An [FeIII 34 ] Molecular Metal Oxide.

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made.

An [FeIII34] Molecular Metal Oxide

AbstractThe dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made.

A cyanide-bridged FeIII-MnII heterobimetallic one-dimensional coordination polymer: synthesis, crystal structure, experimental and theoretical magnetism investigation.

A new cyanide-bridged FeIII-MnII heterobimetallic coordination polymer (CP), namely catena-poly[[[N,N'-(1,2-phenylene)bis(pyridine-2-carboxamidato)-κ4N,N',N'',N''']iron(III)]-μ-cyanido-κ2C:N-[bis(4,4'-bipyridine-κN)bis(methanol-κO)manganese(II)]-μ-cyanido-κ2N:C], {[FeMn(C18H12N4O2)(CN)2(C10H8N2)2(CH3OH)2]ClO4}n, (1), was prepared by the self-assembly of the trans-dicyanidoiron(III)-containing building block [Fe(bpb)(CN)2]- [bpb2- = N,N'-(1,2-phenylene)bis(pyridine-2-carboxamidate)], [Mn(ClO4)2]·6H2O and 4,4'-bipyridine, and was structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction analysis shows that CP 1 possesses a cationic linear chain structure consisting of alternating cyanide-bridged Fe-Mn units, with free perchlorate as the charge-balancing anion, which can be further extended into a two-dimensional supramolecular sheet structure via inter-chain π-π interactions between the 4,4'-bipyridine ligands. Within the chain, each MnII ion is six-coordinated by an N6 unit and is involved in a slightly distorted octahedral coordination geometry. Investigation of the magnetic properties of 1 reveals an antiferromagnetic coupling between the cyanide-bridged FeIII and MnII ions. A best fit of the magnetic susceptibility based on the one-dimensional alternating chain model leads to the magnetic coupling constants J1= -1.35 and J2 = -1.05 cm-1, and the antiferromagnetic coupling was further confirmed by spin Hamiltonian-based density functional theoretical (DFT) calculations.

Surface-Initiated ARGET ATRP of Antifouling Zwitterionic Brushes Using Versatile and Uniform Initiator Film.

In this study, we developed a uniform initiator layer that can be formed on various surfaces, and formed site-selectively, for the subsequent antifouling polymer brush formation. Initially, metal-organic films composed of tannic acid (TA) and FeIII ions (TA-FeIII) were formed on various surfaces, followed by functionalization with an aryl azide-based initiator (ABI) under photoreaction. In particular, combination with a photolithographic technique enabled the presentation of initiators only on the intended region within a single-surface platform. A resultant initiator film (TF-ABI) was formed under mild reaction conditions and meets the uniformity and transparency requirements concurrently. Subsequently, we showed that TF-ABI can be further utilized to form a polymer brush by proceeding with surface-initiated polymerization using a zwitterionic monomer, namely, sulfobetaine acrylamide (SBAA). Instead of applying a classical, yet air-sensitive atom transfer radical polymerization (ATRP) technique, we utilized an activator regenerated by electron transfer (ARGET) ATRP under air conditions without a cumbersome deoxygenation step. Overall, our initiator layer allowed the antifouling poly(SBAA) brush to be used on various surfaces, and enabled their pattern generation.

Enhanced adhesion property of aramid fibers by polyphenol-metal iron complexation and silane grafting

ABSTRACT In this work, a green and efficient method for the surface modification of aramid fibers is proposed, aiming to enhance their adhesion property with rubber matrix. The surface of the aramid fibers was pre-deposited with a polyphenol-metal complex coating via rapid (1 min) complexation between FeIII ions and tannic acid (TA), followed by silane grafting. The influences of reactant concentration and reaction temperature on the grafting efficiency of bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) were also characterized. The adhesion force of the modified aramid fibers/rubber composites showed a maximum improvement of 73.6% compared to that of untreated aramid fibers/rubber composites. This approach showed great potential in rubber industry due to its low-cost and high-efficiency.

Electrochemical development of magnetic long-range correlations with Tc = 128 K in a tetraoxolene-bridged Fe-based framework

The generation of the paramagnetic radical (Cl2An3−) in the framework-edge moieties of an Fe-based two-dimensional honeycomb framework with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinonate (Cl2Ann−), (H3O)2(phz)3[Fe2(Cl2An)3] (phz = phenazine), allowed the formation of long-range magnetic correlations over the network with a relative high magnetic phase transition temperature (Tc) of 128 K. The original compound is a paramagnet with a diamagnetic Cl2An2− linker that significantly separates paramagnetic FeII ions (S = 2), where the [(H3O)2(phz)3]2+ cation is located between layered frameworks. Post-synthetic electron-doping, i.e., reduction in the solid state, using a lithium-ion battery (LIB) system, finally produced (Li+)3(H3O+)2(phz)3[(Fe2+)2(Cl2An3−)3], which demonstrated a drastic magnetic change.

Systematic Design of Crystal Structure for Hofmann-Like Spin Crossover Fe(L)2[Ag(CN)2]2 Complexes

The synthesis, crystal structures, and magnetic properties of a new two-dimensional (2D) Hofmann-like series, FeII(L)2[AgI(CN)2]2 (L = 3-cyano-4-methylpyridine (1), allyl isonicotinate (2), phenyl-isonicotinate (3), and benzyl nicotinate (4)) were studied. These compounds have a 2D sheet structure because of their strongly determinate self-assembly process. An octahedral FeII ion is coordinated with the nitrogen atoms of[AgI(CN)2 linear units at equatorial positions and monodentate pyridine derivatives at the axial position. The layers construct a parallel stacking array. Compounds 1–3 show pairs of layers constructed by intermetallic Ag···Ag interactions. Compound 4 shows a mono-layer structure. The substituent bulk of the ligands affects the interlayer space. Compounds 1–4 undergo a 100% spin transition. However, compound 1, incorporating a smaller group, has a relatively lower critical temperature (Tc = 182 K (1), Tc = 221 K (2), Tc = 227 (3) and Tc1 = 236 K, Tc2 = 215 K (4)). We investigated the correlations between our systematic crystal design, substituent size, and the spin crossover profiles.

Hydrolysis and degradation of dazomet with pyrite: Implications for persistence in produced waters in the Marcellus Shale

Hydraulic fracturing and horizontal drilling in the Marcellus Shale present a novel use of chemical additives at unprecedented volumes. Reuse of produced water has become a popular option in Pennsylvania, complicating our understanding of the fate of chemical additives due to the variability of produced water chemistry. This study investigates the effect of pH, temperature, ionic strength and the presence of pyrite on the kinetics of degradation of dazomet, a commonly-used biocide, under a range of conditions expected during hydraulic fracturing. The results show that the degradation rate of dazomet is highly dependent on many of the variables tested. The hydrolysis is base-catalyzed over the pH range of interest which results in half-lives decreasing from 8.5 h to 3.4 h as the pH is increased from 4.1 to 8.2. Dissolved FeII ions catalyze dazomet degradation kinetics with solutions of 0.8 mM FeII causing degradation rates to increase by 190% over iron-free water. Increasing temperatures from 34 °C to 57 °C quadrupled hydrolysis rates (estimated activation energy of 60 kJ/mol). Reaction with oxygen-exposed pyrite surface led to accelerated degradation of dazomet, but unoxidized pyrite had no effect on the degradation rate of dazomet. The key hydrolysis products of dazomet degradation are formaldehyde and methyl isothiocyanate which are shown to be significantly more toxic than the parent compound. The study points to the need to assess the specific environmental conditions and any toxic by-products in conducting risk assessments for geological applications.

Crystal structure of a low-spin poly[di-μ3-cyanido-di-μ2-cyanido-bis-(μ2-2-ethyl-pyrazine)-dicopper(I)iron(II)

In the title metal-organic framework, [Fe(C6H8N2)2{Cu(CN)2}2] n , the low-spin FeII ion lies at an inversion centre and displays an elongated octa-hedral [FeN6] coordination environment. The axial positions are occupied by two symmetry-related bridging 2-ethyl-pyrazine ligands, while the equatorial positions are occupied by four N atoms of two pairs of symmetry-related cyanide groups. The CuI centre is coordinated by three cyanide carbon atoms and one N atom of a bridging 2-ethyl-pyrazine mol-ecule, which form a tetra-hedral coordination environment. Two neighbouring Cu atoms have a short Cu⋯Cu contact [2.4662 (7) Å] and their coordination tetra-hedra are connected through a common edge between two C atoms of cyanide groups. Each Cu2(CN)2 unit, formed by two neighbouring Cu atoms bridged by two carbons from a pair of μ-CN groups, is connected to six FeII centres via two bridging 2-ethyl-pyrazine mol-ecules and four cyanide groups, resulting in the formation of a polymeric three-dimensional metal-organic coordination framework.

1-D Chain Tungstotellurate Hybrids Constructed from Organic-Ligand-Connecting Iron-Lanthanide Heterometal Encapsulated Tetrameric Polyoxotungstate Units.

A family of inorganic-organic hybrid one-dimensional (1-D) chain iron-lanthanide (Ln) heterometal encapsulated tungstotellurates [H2N(CH3)2]8K2Na4[Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2][Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]·50H2O [Ln = Eu3+ (1), Tb3+ (2), Dy3+ (3), Er3+ (4), HAc = acetate acid, H2pdca = 2,5-pyridinedicarboxylic acid] were prepared using a facile "one-pot" reaction. The molecular structures of 1-4 consist of an intriguing organic-ligand-connecting Fe-Ln heterometal inserted tetrameric unit [Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2][Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]14-. Appealingly, the tetrameric unit is composed of two sandwich-type subunits [Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2]8- and [Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]6-, in which each sandwich-type subunit can be regarded as a derivative of two Ln-organic complexes substituting two external FeIII ions in the classic Krebs-type [Fe4(H2O)10(β-TeW9O33)2]4- fragment. Furthermore, adjacent tetrameric units are interconnected into a 1-D chain arrangement by Hpdca- bridges. 1-4 represent the first examples of Fe-Ln heterometal encapsulated tungstotellurates. Comprehensive magnetic measurements of 3 imply the possible single-molecule magnet properties in 3 with an estimated relaxation time τ0 ≈ 6.06 × 10-6 s at Hdc = 0 Oe and τ0 ≈ 6.97 × 10-5 s at Hdc = 1500 Oe. In addition, the solid-state photoluminescence spectra of 1 and 2 at room temperature exhibit the typical f-f transitions of Ln cations. The Commission International d'Eclairage (CIE) color coordinates of (0.540 24, 0.442 44) for 1 and (0.428 71, 0.428 30) for 2 along with the correlated color temperatures of 1995 and 3278 K, dominant wavelengths of 586 and 578 nm, and color purities of 95.09% and 57.27% for 1 and 2 are obtained.

Crystal structure of catena-poly[[gold(I)-μ-cyanido-[di-aqua-bis-(2-phenyl-pyrazine)-iron(II)]-μ-cyanido] dicyanidogold(I)

In the title polymeric complex, {[Fe(CN)2(C10H8N2)2(H2O)2][Au(CN)2]} n , the FeII ion, which is located on a twofold rotation axis, has a slightly distorted FeN4O2 octa-hedral geometry. It is coordinated by two phenyl-pyrazine mol-ecules, two water mol-ecules and two di-cyano-aurate anions, the Au atom also being located on a second twofold rotation axis. In the crystal, the coordinated di-cyano-aurate anions bridge the FeII ions to form polymeric chains propagating along the b-axis direction. In the crystal, the chains are linked by Owater-H⋯Ndi-cyano-aurate anions hydrogen bonds and aurophillic inter-actions [Au⋯Au = 3.5661 (3) Å], forming layers parallel to the bc plane. The layers are linked by offset π-π stacking inter-actions [inter-centroid distance = 3.643 (3) Å], forming a supra-molecular metal-organic framework.

A Biomimetic Coordination Nanoplatform for Controlled Encapsulation and Delivery of Drug-Gene Combinations.

Inspired by natural biomineralization processes, a simple and universal strategy is introduced to construct a biomimetic nanoplatform for systemic codelivery of a nucleic acid therapeutic (G3139) and a chemotherapeutic drug doxorubicin (DOX). This codelivery system was synthesized through one-pot supramolecular self-assembly of G3139, DOX, and FeII ions through multiple coordination interactions, followed by an adapted surface mineralization with metal-organic frameworks. The resulting core-shell nanoparticles have uniform size, well-defined nanosphere structure, robust colloidal stability, ultrahigh drug loading efficiency and capacity, and precisely adjustable ratios of two therapeutic agents. The system can efficiently accumulate in the tumor, allowing for sensitive MRI detection and synergistical inhibition of tumor growth without apparent systemic toxicity.

Crystal structure, synthesis and thermal properties of tetra-kis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)iron(II).

The asymmetric unit of the title compound, [Fe(NCS)2(C12H9NO)4], consists of an FeII ion that is located on a centre of inversion, as well as two 4-benzoyl-pyridine ligands and one thio-cyanate anion in general positions. The FeII ions are coordinated by two N-terminal-bonded thio-cyanate anions and four 4-benzoyl-pyridine ligands into discrete complexes with a slightly distorted octa-hedral geometry. These complexes are further linked by weak C-H⋯O hydrogen bonds into chains running along the c-axis direction. Upon heating, this complex loses half of the 4-benzoyl-pyridine ligands and transforms into a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, that might be isotypic to the corresponding MnII compound and for which the structure is unknown.

Dicyanometalates as Building Blocks for Multinuclear Iron(II) Spin-Crossover Complexes.

A synthetic strategy featuring dicyanometalates [M(CN)2]- (M = Ag, Au) as N-coordinating ditopic linkers connecting partially blocked FeII centers has been employed to produce heterometallic hexanuclear complexes, which exhibit spin-crossover (SCO) behavior at the FeII sites. The reaction between tris(2-pyridylmethyl)amine (tpma)-capped FeII ions and [Ag(CN)2]- proceeded with partial decomposition of the dicyanoargentate and led to the formation of {[Fe(tpma)]4(μ-CN)2[μ-Ag(CN)2]2}(ClO4)4·3H2O (1), in which both [Ag(CN)2]- and CN- act as bridging ligands, and the opposite [Ag(CN)2]- bridges are engaged in a pronounced argentophilic d10-d10 interaction. In an analogous synthesis, the more stable [Au(CN)2]- species remained intact and furnished the complex {[Fe(tpma)]2[μ-Au2(CN)4]2} (2), which features two FeII centers bridged by two [Au2(CN)4]2- dimers. The use of S,S'-bis(2-pyridylmethyl)-1,2-thioethane (bpte) as a mixed-donor, N2S2-coordinating capping ligand yielded {[Fe(bpte)]2[μ-Au2(CN)4]2} (3), with a structure analogous to that of 2. Variable-temperature magnetic susceptibility measurements revealed that complexes 1-3 exhibit an onset of SCO above 350 K. Measurements above 400 K further confirmed the occurrence of a gradual spin-state conversion for complex 2.

Crystal structure of bis-(4-meth-oxy-pyridine-κN)(meso-5,10,15,20-tetra-phenyl-porphyrinato-κ4 N,N',N'',N''')iron(III) perchlorate.

In the crystal structure of the title compound, [Fe(C44H28N4)(C6H7NO)2]ClO4, the FeIII ions are coordinated in an octa-hedral fashion by four N atoms of the porphyrin moiety and two N atoms of two 4-meth-oxy-pyridine ligands into discrete complexes that are located on inversion centers. Charge-balance is achieved by perchlorate anions that are disordered around twofold rotation axes. In the crystal structure, the discrete cationic complexes and the perchlorate anions are arranged into layers with weak C-H⋯O inter-actions between the cations and the anions. The porphyrin moieties of neighboring layers show a herringbone-like arrangement.

Tuning the Magnetization Dynamic Properties of Nd⋅⋅⋅Fe and Nd⋅⋅⋅Co Single-Molecular Magnets by Introducing 3 d-4 f Magnetic Interactions.

By using paramagnetic [Fe(CN)6 ]3- anions in place of diamagnetic [Co(CN)6 ]3- anions, two field-induced mononuclear single-molecular magnets, [Nd(18-crown-6)(H2 O)4 ][Co(CN)6 ]⋅2 H2 O (1) and [Nd(18-crown-6)(H2 O)4 ][Fe(CN)6 ]⋅2 H2 O (2), have been synthesized and characterized. Single-crystal X-ray diffraction analysis revealed that compounds 1 and 2 were ionic complexes. The NdIII ions were located inside the cavities of the 18-crown-6 ligands and were each bound by four water molecules on either side of the crown ether. Magnetic investigations showed that these compounds were both field-induced single-molecular magnets. By comparing the slow relaxation behaviors of compounds 1 and 2, we found significant differences between the direct and Raman processes for these two complexes, with a stronger direct process in compound 2 at low temperatures. Complete active space self-consistent field (CASSCF) calculations were also performed on two [Nd(18-crown-6)(H2 O)4 ]3+ fragments of compounds 1 and 2. Ab initio calculations showed that the magnetic anisotropies of the NdIII centers in complexes 1 and 2 were similar to each other, which indicated that the difference in relaxation behavior was not owing to the magnetic anisotropy of NdIII . Our analysis showed that the magnetic interaction between the NdIII ion and the low-spin FeIII ion in complex 2 played an important role in enhancing the direct process and suppressing the Raman process of the single-molecular magnet.

A {Tb2Fe3} Pyramid Single‐Molecule Magnet with Ferromagnetic Tb‐Fe Interaction

Summary of main observation and conclusionThe influence of magnetic interactions to the magnetization dynamics was well experimentally studied in a 3d‐4f single‐molecule magnet (SMM) [TbIII2FeIII3(μ5‐O)L2(NO3)4Cl] (1, H4L = N,N,N’,N’‐tetrakis(2‐hydroxyethyl)ethylene diamine) and its diamagnetic‐ ion‐diluted samples. Significant ferromagnetic coupling between TbIII and FeIII ions and SMM behavior of 1 were observable, which proved clearly that the magnetic interaction between 3d‐4f spin carriers has also an excessive impact on fine‐tuning the magnetization dynamic behaviors of 3d‐4f complexes.

An Air-Stable Fe(II) Complex with a Fish and Fish-Net Like Supramolecular Framework: Synthesis, Structure, Magnetic Properties and DFT Investigation

A new H3O+ ions containing air stable complex [FeII(CN)6][(CH3)4N]2(H3O)2 (1) with fish-net like {[FeII(CN)6](H3O)2}2- anions and fish like tetramethylammonium cations is obtained. The crystal structure and magnetic properties have been characterized. The study of the magnetism reveals that the typical diamagnetism of low spin (LS) FeII. The presence of H3O+ ions prevents FeII ions from oxidation in the system, which is proved by DFT investigation and offering a handy approach to obtain the stable FeII ion containing material hard to prepare previously. The hydrogen bonding network might be interesting to the proton conductivity research, as well.

Synthesis, structures and magnetic properties of cyano- and amide-bridged FeIII-LnIII tetranuclear heterometallic clusters

Three FeIII2LnIII2 tetranuclear heterometallic clusters, [H4LGd(H2O)Tp*Fe(CN)3]2·8H2O·2MeOH (1) and [H4LLn(MeOH)Tp*Fe(CN)3]2·6MeOH·2MeCN (Ln = Tb and Dy for 2 and 3, respectively, H6L = N,N′-(2,6-pyridine-dicarboxyl)-disalicylhydrazide, Tp* = hydridotris(3,5dimethylpyrazol-1-yl)-borate), were synthesized by use of the [(Tp*)Fe(CN)3]− unit as a metalloligand toward LnCl3 and H6L species. Structural analyses reveal that FeIII and LnIII ions in all complexes are connected to each other by one cyanide to form a heterobinuclear unit of [Ln(H4L)][(Tp*)Fe(CN)3], which is dimerized through Ln–N–C = O–Ln interaction. Magnetic susceptibility measurements show weak antiferromagnetic interactions between cyano-bridged FeIII and GdIII ions and amide-bridged GdIII ions are operative. Complex 1 displays the magnetocaloric effect with −ΔSmmax = 12.70 J·kg−1·K−1 at 4.0 K for ΔH = 7 T. No single-molecule magnetic properties are observed for 2 or 3 down to 1.8 K.

Surface Deposition of Juglone/FeIII on Microporous Membranes for Oil/Water Separation and Dye Adsorption.

Deposition of dopamine and tannic acid has received great attention in the fields of surface and interface science and technology. The deposition behaviors of various metal-phenolic systems have been investigated, and it is generally accepted that at least one catechol group is essential to the formation of the coatings. Herein, we report a novel and effective surface-coating system based on the coordination complexes of FeIII ions with a natural product juglone that contains only one phenolic hydroxyl. We investigated the deposition behaviors of this novel system on various substrates. Microporous polypropylene membrane modified with juglone/FeIII coatings is superhydrophilic and underwater superoleophobic, showing high separation efficiency and good reusability for various oil/water emulsions. In addition, the modified membrane can adsorb anionic dyes and selectively remove them from dye mixtures with high efficiency. We further demonstrated that the coating is a result of the synergetic effect of juglone/FeIII coordination and FeIII hydrolysis. This work not only provides new insights into surface deposition systems but also expands the polyphenol family for surface coatings of multifunctional materials.