FeIII Ions Research Articles

A Series of Linear {FeIII2 FeII } Complexes with Paramagnetic Building-Block-Modified Spin Crossover Behaviors.

Tuning of the spin crossover (SCO) behavior through paramagnetic building blocks with different steric hindrance effects is of great interest in terms of the synergy between SCO and magnetic interactions. Herein, the steric effect of specified FeIII building blocks is modified, from the large Tp* (hydridotris(3,5-dimethylpyrazol-1-yl)borate) analogue to a small Tp (hydrotris(pyrazolyl)borate) derivative; the FeII SCO unit and FeIII paramagnetic ions are incorporated into three well isolated trinuclear complexes featuring thermally induced and light-induced SCO properties. Reanalysis of the structures reveals that π-π stacking interactions play a key role in the thermal hysteresis and anomalous octahedral distortion parameter Σ around the FeII ion. The Tp* ligand showing the largest steric hindrance induces elongated FeII -N bond lengths and bending of the C≡N-FeII angle in 1, as well as having a relatively large electron donor effect, which leads to the lowest thermal transition temperature among the three compounds.

Synergistic treatment of triple-negative breast cancer by doxorubicin and thioridazine and its nano-formulation

Three new trinuclear hetero-metallic complexes, [(NiLR)2Fe(N3)3] (1), [(NiLR(H2O))2Fe(C6H5CH2CO2)2]·(HSO4) (2) and [(NiLR(H2O))2Fe(C6H5CO2)2]·(HSO4)·(H2O)·(CH2Cl2) (3) have been synthesized using [NiLR] as a “metalloligand” (where H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic study. In the angular trinuclear units of 1, the two terminals [NiLR] coordinate through double phenoxido bridges to the central FeIII ion which is penta-coordinated having terminally coordinated azide ion. The two terminal NiII centers are connected to each other and also to neighbouring units through μ1,3-azido bridges to form an alternating chain. On the other hand, complexes, 2 and 3 are linear discrete trinuclear species [NiII–FeIII–NiII] in which two terminal octahedral [NiLR] units coordinate to the central octahedral FeIII ion, located on a crystallographic centre of symmetry, through a μ2-phenoxido oxygen atom and a bridging carboxylato ion. Variable temperature magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions in 1 mediated through the phenoxido bridges (J1 = −33.2 cm−1,) and μ1,3-N3 single bridges (J2 = −19.9 cm−1 and J3 = −16.7 cm−1). On the other hand, compounds 2 and 3 show ferromagnetic coupling interactions mediated through the double phenoxido bridges with J values of +4.9 and +3.0 cm−1 for 2 and 3, respectively.

On the Effect of the Internal Pressure on the Photoinduced Spin‐Crossover Behavior of [FexM1–x(1,10‐phenanthroline)2(NCS)2] Solid Solutions (M = NiII, ZnII, and CdII)

The thermal and light‐induced magnetic properties of a family of metal‐diluted spin‐crossover complexes, [FexM1–x(phen)2(NCS)2] (phen = 1,10‐phenantholine and M = NiII, CdII), are reported and compared to previous results obtained for the same series but with ZnII ions used to substitute FeII ions; the ultimate goal was to validate the influence of the size and nature of the inert metal ion on the light‐induced properties of spin‐crossover compounds. For all of the materials, we measured the thermally induced spin‐crossover temperature (T1/2) and T(LIESST) (LIESST = light‐induced excited spin‐state trapping) values systematically. We observed clearly that the dilution has a strong effect on the magnetic and photomagnetic properties. The magnitude of these effects depends strongly on the nature of the diluting metal. This comparison gives insights into the effect of the size of the diluting ion on T(LIESST) and T1/2 and completes the previous studies on the effect of internal pressure on the lifetime of the photoinduced state.

Synthesis, characterization, crystal structure and electrochemical studies of ionic iron(III) dipicolinato complex

The new complex (NH4)[Fe(dipic)2] (1) (dipicH2 = 2,6-pyridinedicarboxylic acid), was synthesized and characterized by elemental analysis, FTIR and UV–Vis spectroscopy and single crystal X-ray method. The crystal system is tetragonal with space group I41/a. The FeIII ion and the N atom of the ammonium cation are located on a crystallographic fourfold rotoinversion axis (4¯). The NH⋯O and CH⋯O intermolecular hydrogen bonding and π⋯π stacking interactions play an important role in the formation of a 3-dimensional anion-cation network and stabilization of the crystal structure. The redox behavior of the complex was also investigated by cyclic voltammetry.

Bromidocarbonyl{(1S,2S)-N-[2-(dicyclohexylphosphanyl)ethylidenyl]-N′-[2-(diphenylphosphanyl)ethyl]-1,2-diphenylethane-1,2-diamine}iron(II) tetraphenylborate

In the title compound, trans-(S,S)-[FeBr(CO)(PPh2CH2CH2NHCHPhCHPhNCHCH2PCy2)]BPh4, the FeII ion is in a distorted octahedral complex geometry with a cis-β ligand geometry in which two diastereomers co-crystallized in the asymmetric unit. These diastereomers differ by the orientation of the N—H moieties on the ligand; one is in the S conformation (A), and the other R (B). Diasteromer A has a P—Fe—P angle of 104.36 (6)° and B has a P—Fe—P angle of 102.70 (6)°. During the refinement of the structure, electron density peaks were located that were believed to be highly disordered solvent molecules (possibly diethyl ether). Attempts made to model the solvent molecule were not successful. The SQUEEZE [Spek (2015). Acta Cryst. C71, 9–18] option in PLATON indicated there was a large solvent cavity of 363 Å3. In the final cycles of refinement, this contribution of 117 electrons to the electron density was removed from the observed data. The density, the F(000) value, the molecular weight and the formula are given without taking into account the results obtained with SQUEEZE.

Mössbauer Spectra of Mouse Hearts Reveal Age-dependent Changes in Mitochondrial and Ferritin Iron Levels

Cardiac function requires continuous high levels of energy, and so iron, a critical player in mitochondrial respiration, is an important component of the heart. Hearts from 57Fe-enriched mice were evaluated by Mössbauer spectroscopy. Spectra consisted of a sextet and two quadrupole doublets. One doublet was due to residual blood, whereas the other was due to [Fe4S4]2+ clusters and low-spin FeII hemes, most of which were associated with mitochondrial respiration. The sextet was due to ferritin; there was no evidence of hemosiderin, a ferritin decomposition product. Iron from ferritin was nearly absent in young hearts, but increased steadily with age. EPR spectra exhibited signals similar to those of brain, liver, and human cells. No age-dependent EPR trends were apparent. Hearts from HFE-/- mice with hemochromatosis contained slightly more iron overall than controls, including more ferritin and less mitochondrial iron; these differences typify slightly older hearts, perhaps reflecting the burden due to this disease. HFE-/- livers were overloaded with ferritin but had low mitochondrial iron levels. IRP2-/- hearts contained less ferritin than controls but normal levels of mitochondrial iron. Hearts of young mice born to an iron-deficient mother contained normal levels of mitochondrial iron and no ferritin; the heart from the mother contained low ferritin and normal levels of mitochondrial iron. High-spin FeII ions were nearly undetectable in heart samples; these were evident in brains, livers, and human cells. Previous Mössbauer spectra of unenriched diseased human hearts lacked mitochondrial and blood doublets and included hemosiderin features. This suggests degradation of iron-containing species during sample preparation.

Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings.

A family of wheel-shaped charge-neutral heterometallic {FeIII4LnIII2}- and {FeIII18MIII6}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe4Ln2}-type compounds [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(EtOH), Ln = Dy (1a), Er (1b), Ho (1c); [Fe4Tb2(O2CCMe3)6(N3)4(Htea)4] (1d); [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(CH2Cl2), Ln = Dy (2a), Er (2b); [Fe4Ln2(O2CCMe3)4(N3)6(Htea)4]·2(EtOH)·2(CH2Cl2), Ln = Dy (3a), Er (3b) and the {Fe18M6}-type compounds [Fe18M6(O2CCHMe2)12(Htea)18(tea)6(N3)6]·n(solvent), M = Dy (4, 4a), Gd (5), Tb (6), Ho (7), Sm (8), Eu (9), and Y (10) form in ca. 20–40% yields in direct reaction of trinuclear FeIII pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H3tea) and azide ligands in different solvents: EtOH for the smaller {Fe4Ln2} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe18M6} wheels. Single-crystal X-ray diffraction analyses revealed that 1–3 consist of planar centrosymmetric hexanuclear clusters built from FeIII and LnIII ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in 1a–c, 2 CH2Cl2 in 2, and 2 EtOH and 2 CH2Cl2 in 3). In 4–10, the largest 3d/4f wheels currently known, nearly linear Fe3 fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of 1–10 reveal slow magnetization relaxation for {Fe4Tb2} (1d) and slow relaxation for {Fe4Ho2} (1c), {Fe18Dy6} (4), and {Fe18Tb6} (6).

C=N Bond Activation and Hydration by an Iron(III) Complex with Asymmetric Sulfur Oxygenation

The presence of asymmetric cysteine sulfur‐oxygenation donors, consisting of sulfenate (SO), sulfinate (SO2), and thiolate (S), around a trivalent iron is essential for the catalytic function of Fe‐ or Co‐type nitrile hydratase (NHase). To gain insight into the role of this asymmetric ligation, an octahedral bisthiolate low‐spin FeIII complex and two of its S‐oxygenation derivatives, unprecedented mixed sulfinate/thiolate and O‐bound bissulfinate complexes, were generated. The placement of anionic nitrogen atoms trans to the thiolates in the bisthiolate complex caused the axial imino C=N bonds to be more polarized and thus resembled the activation of bound nitrile in nitrile hydratase. The polarization was found to be even more severe in the monosulfinate species, and hydration of the Fe‐bound C=N bond by HO– was observed. The generation of an O‐bound bissulfinate octahedral complex implied that the equatorial carboxamido and axial thiolate ligation in Fe‐NHase provided greater electron buffering capacity in keeping the electron density of the FeIII ion constant even in the presence of equatorial S‐oxygenations.

Green-to-Red Electrochromic Fe(II) Metallo-Supramolecular Polyelectrolytes Self-Assembled from Fluorescent 2,6-Bis(2-pyridyl)pyrimidine Bithiophene.

The structure and properties of metallo-supramolecular polyelectrolytes (MEPEs) self-assembled from rigid 2,6-bis(2-pyridyl)pyrimidine and the metal ions FeII and CoII are presented. While FeL1-MEPE (L1 = 1,4-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]benzene) is deep blue, FeL2- and CoL2-MEPE (L2 = 5,5'-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]-2,2'-bithiophene) are intense green and red in color, respectively. These novel MEPEs display a high extinction coefficient and solvatochromism. Ligand L2 shows a high absolute fluorescence quantum yield (Φf = 82%). Viscosity and static light-scattering measurements reveal that the molar masses of these MEPEs are in the range of 1 × 108 g/mol under the current experimental conditions. In water, FeL1-MEPE forms a viscous gel at 20 °C (c = 8 mM). Thin films of high optical quality are fabricated by dip coating on transparent conducting indium tin oxide (ITO) glass substrate. Optical, electrochemical, and electrochromic properties of the obtained MEPEs are presented. Green to red and blue to colorless electrochromism is observed for FeL2-MEPE and FeL1-MEPE, respectively. The results show that the electrochromic properties are affected by the ligand topology. The Fe-MEPEs show a reversible redox behavior of the FeII/FeIII couple at 0.86 and 0.82 V versus Fc+/Fc and display an excellent redox cycle stability under switching conditions. FeL2-MEPE in its oxidized state exhibits a broad absorption band covering the near-IR region (ca. 1500 nm) due to the ligand-to-metal charge transfer transition originating due to charge delocalization in the bithiophene spacer.

The magnetoresistance effect in a conducting molecular crystal consisting of dicyano(phthalocyaninato)manganese(iii).

A conducting molecular crystal TPP[MnIII(Pc)(CN)2]2 (MnIII: d4, S = 1, TPP = tetraphenylphosphonium and Pc = phthalocyanine) was fabricated. In its crystal structure, the [MnIII(Pc)(CN)2] units formed a one-dimensional regular chain along the c-axis with an overlap integral value of 8.6 × 10-3. TPP[MnIII(Pc)(CN)2]2 showed a semiconducting behaviour that also has been observed for isostructural TPP[CoIII(Pc)(CN)2]2 (CoIII: d6, S = 0) and TPP[FeIII(Pc)(CN)2]2 (FeIII: d5, S = 1/2) whose ground states are charge-ordered states. In spite of the local magnetic moment of the MnIII ion (S = 1) at the centre of the Pc ligand, TPP[MnIII(Pc)(CN)2]2 exhibited an almost isotropic and small negative magnetoresistance (MR) effect (the MR ratio was -8.7% under 8 T at 10.7 K), contrarily to the anisotropic giant negative MR effect of TPP[FeIII(Pc)(CN)2]2. The isotropy was found to be due to a (dxz)1(dyz)1 electronic configuration, and the smaller MR effect was explained by a weaker antiferromagnetic interaction between MnIII ions than that between FeIII ions, as suggested by a Weiss temperature Θ of -3.1 K (|Jdd|/kB = 1.2 K).

Syntheses and Structure Investigations of 3d Transition Metal Complexes with a Flexible N4O2-Donor Hexadentate Schiff-Base Ligand

The syntheses and structure investigations of four new 3d transition metal complexes (1–4) with a flexible N4O2-donor hexadentate Schiff-base ligand are described; three complexes (1, 2, and 4) of FeIII, CoIII, and CuII metal ions have been investigated by UV-vis, FT-IR, high-resolution mass spectrometry (HR-MS), and scanning electron microscopy–electron dispersive spectroscopy, as well as single crystal X-ray diffraction. The X-ray structure of NiII complex 3 is also reported. The molecular structures of the complexes (1–3) demonstrate distorted octahedral coordination geometry, each exhibiting 1 : 1 (M : L) ratios and the CuII complex 4 shows a trinuclear structure with a CuII : L ratio of 3 : 2 in the solid state, which has been proven by X-ray diffraction. On the other hand, a mononuclear species of the CuII complex is formed in solution, which has been identified by electrospray ionization HR-MS.

Syntheses, Structures, Luminescence, and Magnetic Properties of a Series of Novel Coordination Polymers Constructed by Nanosized [Ln8Fe4] Rings

A total of five three-dimensional Ln-Fe coordination polymers (CPs) [(CH3)2NH][(CH3)2NH2][Ln2Fe(SO4)4(L)]·3H2O (Ln = Eu, 1; Dy, 2; Gd, 3; Sm, 4; Er, 5; H2L = tartaric acid) have been successfully synthesized under solvothermal conditions and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analyses, luminescence, and magnetic properties. Structural analysis indicates that the frameworks of 1–5 are constructed from novel [Ln8Fe4] rings. In the strcutures of 1–5, LnIII and FeIII ions interconnect through O donors of sulfate anions to generate a one-dimensional chain, and the adjacent chains are joined together by ligand [L]2– to form a two-dimensional zonary plane, which is further bridged by ligand [L]2– to give a new topology and named as “Xhd1”. Magnetic properties of 2 and 3 were investigated using variable temperature magnetic susceptibility, and weak ferromagnetic exchange between the FeIII and LnIII ions has been established for the Gd derivative. Meanwhile, we also studi...

Crystal structure of bis-(bis-{μ3-3-methyl-3-[(4-nitro-2-oxido-benzyl-idene)amino]-propane-1,3-diolato}tris-[chlorido-(dimethyl sulfoxide)-iron(III)]) dimethyl sulfoxide hepta-solvate dihydrate.

The title compound, [Fe3(C11H11N2O5)2Cl3(C2H6OS)3]2·7C2H6OS·2H2O, was isolated accidentally from an Fe0-NiCl2·6H2O-H3L-TEA-DMSO system [where H3L is the product of the condensation between p-nitro-salicyl-aldehyde and 2-amino-2-methyl-propane-1,3-diol and dimethyl sulfoxide (DMSO), and TEA is triethylamine]. The structure is based on a trinuclear {Fe3(μ-O)4} core, with an angular arrangement of the FeIII ions that can be explained by the geometrical restrictions of two bulky ligands, each coordinating to all of the metal cations.

Cage-like Fe,Na-Germsesquioxanes: Structure, Magnetism, and Catalytic Activity.

A series of four unprecedented heterometallic metallagermsesquioxanes were synthesized. Their cage-like architectures have a unique type of molecular topology consisting of the hexairon oxo {Fe6 O19 } core surrounded in a triangular manner by three cyclic germoxanolates [PhGe(O)O]5 . This structural organization induces antiferromagnetic interactions between the FeIII ions through the oxygen atoms. Evaluated for this first time in catalysis, these compounds showed a high catalytic activity in the oxidation of alkanes and the oxidative formation of benzamides from alcohols.

Cage‐like Fe,Na‐Germsesquioxanes: Structure, Magnetism, and Catalytic Activity

AbstractA series of four unprecedented heterometallic metallagermsesquioxanes were synthesized. Their cage‐like architectures have a unique type of molecular topology consisting of the hexairon oxo {Fe6O19} core surrounded in a triangular manner by three cyclic germoxanolates [PhGe(O)O]5. This structural organization induces antiferromagnetic interactions between the FeIII ions through the oxygen atoms. Evaluated for this first time in catalysis, these compounds showed a high catalytic activity in the oxidation of alkanes and the oxidative formation of benzamides from alcohols.

Magnetic Bistability in Macrocycle‐Based FeII Spin‐Crossover Complexes: Counter Ion and Solvent Effects

Two new iron(II) complexes of formula [Fe(L2)](tcm)2·2H2O (1) and [Fe(L2)][Ni(CN)4]·H2O (2) {L2 = 1,8‐bis(2′‐pyridylmethyl)‐1,4,8,11‐tetraazacyclotetradecane; tcm– = [C(CN)3]– = tricyanomethanide anion} have been synthesized and characterized by X‐ray diffraction and magnetic measurements and compared with the previously described compound of the same series [Fe(L2)](BF4)2·H2O (3). The crystal structures of the three compounds show discrete iron(II) complexes in which the FeII ions adopt distorted FeN6 octahedral geometries. A hydrogen‐bonding network involving the water molecules and the different counter ions, tcm– in 1 and [Ni(CN)4]2– in 2, leads to chains for both compounds whereas compound 3 reveals no significant intermolecular contacts. For 1, the magnetic measurements show an abrupt and incomplete high‐spin→low‐spin (HS→LS) spin transition (ST) with a hysteresis of 9 K (T1/2down = 136 K; T1/2up = 145 K) that is also optically observed. Compound 2 presents slightly weaker intermolecular contacts and shows an abrupt ST at 85 K without hysteretic behaviour. Finally, compound 3, in which the FeII complex is well isolated, exhibits a gradual spin transition centred at 150 K. Detailed X‐ray diffraction studies performed at various temperatures (293–120 K) show strong modifications of the iron coordination sphere in 1 and 3, in agreement with the presence of a ST in this temperature range in both complexes.

One‐Step Assembly of Phytic Acid Metal Complexes for Superhydrophilic Coatings

AbstractWhile of immense scientific interest, superhydrophilic surfaces are usually difficult to prepare, and preparation methods are typically substrate specific. Herein, a one‐step coating method is described that can endow superhydrophilicity to a variety of substrates, both inorganic and organic, using the coordination complexes of natural phytic acid and FeIII ions. Coating deposition occurs in minutes, and coatings are ultrathin, colorless, and transparent. Superhydrophilicity is attributed, in part, to the high density of phosphonic acid groups. The ease, rapidness, and mildness of the assembly process, which is also cost‐effective and environmental‐friendly, points towards potential applications, such as self‐cleaning, oil/water separation, antifogging.

Tri‐ and Pentanuclear Complexes Derived from Manganese(III) Schiff Base and Hexacyanoferrate(III) Building Blocks

A tri‐ and a pentanuclear cyanido‐bridged complex based on manganese(III) Schiff base and hexacyanoferrate(III) units, namely, [{Mn(naphtmen)}2{Fe(CN)6}][Mn(naphtmen)(CH3OH)2]2ClO4·5CH3OH·H2O [1; naphtmen2– = N,N′‐(1,1,2,2‐tetramethylethylene)bis(naphthylideneiminato) dianion] and [{Mn(naphtmen)}4{Fe(CN)6}]ClO4 (2), were synthesized and structurally characterized by X‐ray single‐crystal diffraction. The structural analyses show that 1 consists of linear trinuclear clusters of [{Mn(naphtmen)}2{Fe(CN)6}]– anions, which are further linked into one‐dimensional chains by the out‐of‐plane biphenolate bridges. In 2, magnetically isolated cyanido‐bridged pentanuclear {[Mn(naphtmen)]4[Fe(CN)6]}+ cations were obtained. The temperature‐dependent magnetic susceptibilities indicate that the exchange interactions between the FeIII and MnIII ions through the cyanido bridges are ferromagnetic in 1 and 2. The magnetic fittings for 1 and 2 gave magnetic coupling constants JMnFe = 6.68 and 4.31 cm–1, respectively. Complex 2 exhibits a clear frequency‐dependent alternating‐current (AC) magnetic susceptibility below 3.5 K, which is due to single‐molecule magnet behavior with Ueff = 23.4 cm–1 and τ0 = 7.5 × 10–10 s.

Anion-Directed Entangling Coordination Networks: Luminescence Sensing and Magnetic Properties.

Solvothermal reactions of a bifunctional ligand 4-(2-ethyl-1H-imidazol-1-yl)benzoic acid (2-Heiba) with Cu(NO3 )2 and Cu(OAc)2 afforded two coordination polymers, [Cu3 (2-eiba)4 (NO3 )2 ]⋅5 DMF (1; DMF= N,N-dimethylformamide) and [Cu(2-eiba)2 ] (2), respectively, which show a twofold interpenetrated 3D network and 2D+2D→3D polycatenated architecture. Complex 1 is a potential luminescent detector for nitrobenzene and FeIII ions, whereby strong antiferromagnetic interactions are also found between the CuII centers.

Intra‐ and inter‐supramolecular complexation of poly(butyl methacrylate)‐co‐2‐(1,2,3‐triazol‐4‐yl)pyridine copolymers induced by CoII, FeII, and EuIII ions monitored by molecular hydrodynamics methods

ABSTRACTPoly(butyl methacrylate) copolymers embedding bidentate 2‐(1,2,3‐triazol‐4‐yl)pyridine (trzpy) chelating units as comonomer in the side chains were synthesized by controlled radical addition‐fragmentation transfer (RAFT) polymerization. Intracomplexation and intercomplexation of the macromolecules of the poly(butyl methacrylate) copolymers containing 20 % mol of trzpy units induced by CoII, FeII, and EuIII ions were studied in the solutions by macromolecular hydrodynamics methods. The sedimentation velocity of extremely diluted copolymer solutions and the dynamic viscosity of moderately diluted solutions were studied in a wide range of the salts concentrations. Differences were observed with respect to the copolymer behavior in the presence of the Co2+, Fe2+, Eu3+ ions. These differences are namely due to the differences in the number of coordination bonds required for complex formation and not explicitly to the nature of the corresponding anions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2632–2639