Iron Phthalocyanine Complexes Research Articles

A highly efficient iron phthalocyanine-intercalated CuFe-LDH catalyst for the selective oxidation of 5-hydroxymethylfurfural to 5-formyl-2-furanic acid

A catalyst with high selectivity for the catalytic oxidation of 5-hydroxymethylfurfural (HMF) to 5-formyl-2-furanic acid (FFCA) in alkaline media was successfully developed by ultrasonic intercalation of a copper‑iron layered double hydroxide (CuFe-LDH) platelets with an iron phthalocyanine (FePc) complex. The effects of reaction temperature, reaction time, H2O2 concentration, NaOH concentration and amount of catalyst on HMF conversion and FFCA selectivity were systematically investigated. Under the optimized testing condition the developed FePc-CuFe catalyst delivered a HMF conversion of 85% with a FFCA selectivity of 81.8%. Further, the catalyst showed excellent stability over 5 testing cycles.

Application of Lever’s Electrochemical EL Parameters Scale Toward Fe(II)/Fe(III) Versus Pc(2-)/Pc(1-) Oxidation Process Crossover Point in Axially Coordinated Iron(II) Phthalocyanine Complexes and Its Relation to the MLCT1 Energy Derived from MCD Spectroscopy

The electronic structures, and, particularly, the nature of the HOMO in a series of the low-spin PcFeL2, PcFeL′L″, and [PcFeX2]2- iron(II) phthalocyanine complexes were probed by electrochemical, spectroelectrochemical and chemical oxidation approaches and complimented by MCD spectroscopy as well as theoretical (DFT and TDDFT) studies. In general, energies of the metal-centered occupied orbitals in the various six-coordinate iron phthalocyanine complexes correlate well with Lever’s electrochemical parameter, EL, and intercross the phthalocyanine-centered a1u orbital in several compounds with moderate-to-strong p-accepting axial ligands. In these cases, an oxidation of the phthalocyanine macrocycle (Pc(2-)/Pc(1-)) rather than the central metal ion (Fe(II)/Fe(III)) was theoretically predicted and experimentally confirmed. The experimentally derived using MCD spectroscopy or theoretically predicted using TDDFT calculations energy of the MLCT1 transition (dπ→Pc(π*)) on iron(II) phthalocyanines also follows the trend expected for the EL properties of the axial ligands.

Charge-Transfer Spectroscopy of Bisaxially Coordinated Iron(II) Phthalocyanines through the Prism of the Lever's EL Parameters Scale, MCD Spectroscopy, and TDDFT Calculations.

The position of the experimentally observed (in the UV-vis and magnetic circular dichroism (MCD) spectra) low-energy metal-to-ligand charge-transfer (MLCT) band in low-spin iron(II) phthalocyanine complexes of general formula PcFeL2, PcFeL'L″, and [PcFeX2]2- (L, L', or L″ are neutral and X- is an anionic axial ligand) was correlated with the Lever's electrochemical EL scale values for the axial ligands. The time-dependent density functional theory (TDDFT)-predicted UV-vis spectra are in very good agreement with the experimental data for all complexes. In the majority of compounds, TDDFT predicts that the first degenerate MLCT band that correlates with the MCD A-term observed between 360 and 480 nm is dominated by an eg (Fe, dπ) → b1u (Pc, π*) single-electron excitation (in traditional D4h point group notation) and agrees well with the previous assignment discussed by Stillman and co-workers[ Inorg. Chem. 1994, 33, 573-583]. The TDDFT calculations also suggest a small energy gap for b1u/b2u (Pc, π*) orbital splitting and closeness of the MLCT1 eg (Fe, dπ) → b1u (Pc, π*) and MLCT2 eg (Fe, dπ) → b2u (Pc, π*) transitions. In the case of the PcFeL2 complexes with phosphines as the axial ligands, additional degenerate charge-transfer transitions were observed between 450 and 500 nm. These transitions are dominated by a2u (Pc + L, π) → eg (Pc, π*) single-electron excitations and are unique for the PcFe(PR3)2 complexes. The energy of the phthalocyanine-based a2u orbital has large axial ligand dependency and is the reason for a large energy deviation for B1 a2u (Pc + L, π) → eg (Pc, π*) transition. The energies of the axial ligand-to-iron, axial ligand-to-phthalocyanine, iron-to-axial ligand, and phthalocyanine-to-axial ligand charge-transfer transitions were discussed on the basis of TDDFT calculations.

Electrochemical, spectroelectrochemical, electrocatalytic oxygen reducing, and heavy metal ion sensing properties of novel tetrakis-[4-((2, 8-bis (trifluoromethyl) quinolin-4-yl) oxyl)] substituted metallophthalocyanines

Novel tetrakis-[4-((2,8-bis(trifluoromethyl)quinolin-4-yl)oxyl)] substituted phthalocyanine complexes were obtained by the tetramerization reaction of corresponding phthalonitrile derivative with appropriate metal salts under determined conditions. The structures of the complexes were clarified by elemental analysis, fourier transform infrared, ultraviolet–visible and matrix-assisted laser desorption ionization time-of-flight mass spectroscopic methods. The redox properties of zinc, cobalt, and iron phthalocyanines were investigated by voltammetric and colorimetry supported in situ spectroelectrochemical measurements in non-aqueous solution medium. The metal and phthalocyanine ring based redox processes were observed to be associated with distinct spectral and color changes and affected by the presence of molecular oxygen in the medium. Furthermore, oxygen interaction measurements performed during the oxygenation of de-aerated electrolyte solution suggested that the iron phthalocyanine complex possesses oxygen binding capability and has the tendency of forming µ-oxo-dimer complexes and thus, displaying electrocatalytic activity for oxygen reduction reaction. Electrocatalytic oxygen reducing performances of the complexes were investigated in a medium similar to direct methanol or polymer electrolyte membraned fuel-cell working conditions and compared in detail. Iron(II) phthalocyanine complex appeared as suitable electrocatalyst for both polymer electrolyte membraned and direct methanol fuel cells with high catalytic performance towards oxygen reduction and high tolerance to methanol, respectively. The metallophthalocyanines modified quartz crystal microbalance sensors were designed to detect divalent heavy metal ions (cobalt(II), cadmium(II), cupper(II), and zinc(II)) in water samples. Frequency shift measurements of the complexes showed that the possibility of the use of iron(II) phthalocyanine as a novel cadmium(II) ion sensing material, owing to its high sensitivity, reversibility, stability, and the possibility to operate at room temperature.

Application of Lever's EL Parameter Scale toward Fe(II)/Fe(III) versus Pc(2-)/Pc(1-) Oxidation Process Crossover Point in Axially Coordinated Iron(II) Phthalocyanine Complexes.

The electronic structures and, particularly, the nature of the HOMO in a series of PcFeL2, PcFeL'L″, and [PcFeX2]2- complexes (Pc = phthalocyaninato(2-) ligand; L = NH3, n-BuNH2, imidazole (Im), pyridine (Py), PMe3, PBu3, t-BuNC, P(OBu)3, and DMSO; L' = CO; L″ = NH3 or n-BuNH2; X = NCO-, NCS-, CN-, imidazolate (Im-), or 1,2,4-triazolate(Tz-)) were probed by electrochemical, spectroelectrochemical, and chemical oxidation as well as theoretical (density functional theory, DFT) studies. In general, energies of the metal-centered occupied orbitals in various six-coordinate iron phthalocyanine complexes correlate well with Lever Electrochemical Parameter EL and intercross the phthalocyanine-centered a1u orbital in several compounds with moderate-to-strong π-accepting axial ligands. In these cases, an oxidation of the phthalocyanine macrocycle (Pc(2-)/Pc(1-)) rather than the central metal ion (Fe(II)/Fe(III)) was theoretically predicted and experimentally confirmed.

Study of the Interaction of an Iron Phthalocyanine Complex over Surface Modified Carbon Nanotubes.

Carbon nanotubes (CNT) were prepared by a modified chemical vapor deposition (CVD) method. The synthesized carbon materials were treated with acidic and basic solutions in order to introduce certain surface functional groups, mainly containing oxygen (OCNT) or amine (ACNT) species. These modified CNTs (OCNT and ACNT) as well as the originally prepared CNT were reacted with a non-ionic Fe complex, Iron (II) Phthalocyanine, and three composites were obtained. The amount of metal complex introduced in each case and the interaction between the complex and the CNT materials were studied with the aid of various characterization techniques such as TGA, XRD, and XPS. The results obtained in these experiments all indicated that the interaction between the complex and the CNT was greatly affected by the functionalization of the latter.

Accurate Prediction of Mössbauer Hyperfine Parameters in Bis-Axially Coordinated Iron(II) Phthalocyanines Using Density Functional Theory Calculations: A Story of a Single Orbital Revealed by Natural Bond Orbital Analysis.

Density Functional Theory (DFT) calculations coupled with several exchange-correlation functionals were used for the prediction of Mössbauer hyperfine parameters of 36 bis-axially coordinated iron(II) phthalocyanine complexes with the general formulas PcFeL2, PcFeL'L″, and [PcFeX2]2-, including four new compounds. Both gas-phase and PCM calculations using BPW91 and MN12L exchange-correlation functionals were found to accurately predict both Mössbauer quadrupole splittings and the correct trends in experimentally observed isomer shifts. In comparison, hybrid exchange-correlation functionals underestimated quadrupole splittings, while still accurately predicted isomer shifts. Out of ∼40 exchange-correlation functionals tested, only MN12L was found to correctly reproduce quadrupole splitting trends in the PcFeL2 complexes coordinated with phosphorus-donor axial ligands (i.e., P(OnBu)3 ≈ P(OEt)3 < PMe3 < P[(CH2O)2CH2]-p-C6H4NO2 < PEt3 ≈ PnBu3). Natural Bond Orbital (NBO) analysis was successfully used to explain the general trends in the observed quadrupole splitting for all compounds of interest. In particular, the general trends in the quadrupole splitting correlate well with the axial ligand dependent, NBO-predicted population of the 3dz2 orbital of the Fe ion and are reflective of the hypothesis proposed by Ohya and co-workers ( Inorg. Chem., 1984, 23, 1303) on the adaptability of the phthalocyanine's π-system toward Fe-Lax interactions. The first X-ray crystal structure of a PcFeL2 complex with axial phosphine ligands is also reported.

Direct Measurement of Electron Transfer Rates between Iron(II) Phthalocyanine and Gold with Different Interface Structures

Electron transfer in a metal/molecule system has been extensively studied using various methods. In particular, the relation between the structure of metal/molecule junctions and the electron transfer property is of great interest in the research field of molecular devices. In this study, we measured electron transfer rates of iron(II) phthalocyanine/gold system with different junctions to study the contribution of the atomistic interfacial structures to the electron transfer characteristics.An Au single-crystal disk with (111) or (100) orientation was modified with self-assembled monolayers of imidazole-terminated alkanethiols with the alkyl chain of ten carbon atoms (ImC10SH). Then, iron(II) phthalocyanine (FePc) complexes were attached on top of the monolayer through the axial ligation of the central Fe ions with the imidazole groups. The Au-S bonding structure was measured using Surface-enhanced Raman spectroscopy (SERS).1) The electron transfer rate between Au and FePc was measured by analyzing the cyclic voltammogram (CV) of redox behavior for FePc in 0.1 M perchloric acid aqueous solution.SERS measurements showed that the Au-S bonding structures were different between Au(111) and Au(100). According to the peak position of nAu-S, the dominant Au-S structure was determined to be three-fold hollow geometry on Au(111) and two-fold bridge geometry on Au(100). Figure shows the scan rate dependence of CVs of FePc/ImC10SH/Au(100) and FePc/ImC10SH/Au(111). With increasing the scan rate, the peak separation between the oxidation and reduction peaks became larger in both cases. However, the magnitude of the separation was larger for Au(111) than for Au(100), suggesting that the electron transfer through the Au-S junction was slower at the hollow site on Au(111) than at the bridge site on Au(100). The electron transfer rate can be calculated from the relation between the peak separation and the scan rate. We will present detailed quantitative analysis of the electron transfer rate for different Au-S bond structures, alkyl chain lengths, etc.1) M. Inagaki, K. Motobayashi, K, Ikeda, J. Phys. Chem. Lett., 8, 4236 (2017)Figure. Scan rate dependence of CVs of FePc/ImC10SH/Au(100) and, FePc/ImC10SH/Au(111) in 0.1 M perchloric acid aqueous solution. Figure 1

Iron-Catalyzed Synthesis, Structure, and Photophysical Properties of Tetraarylnaphthidines.

We describe the synthesis and photophysical properties of tetraarylnaphthidines. Our synthetic approach is based on an iron-catalyzed oxidative C–C coupling reaction as the key step using a hexadecafluorinated iron–phthalocyanine complex as a catalyst and air as the sole oxidant. The N,N,N’,N’-tetraarylnaphthidines proved to be highly fluorescent with quantum yields of up to 68%.

Iron-Catalyzed Oxidative C-C Cross-Coupling Reaction of Tertiary Anilines with Hydroxyarenes by Using Air as Sole Oxidant.

A mild procedure for the oxidative C−C cross‐coupling of tertiary anilines with phenols is described which provides the products generally in high yields and with excellent selectivity. The reaction is catalyzed by the hexadecafluorinated iron–phthalocyanine complex FePcF16 in the presence of substoichiometric amounts of methanesulfonic acid and ambient air as sole oxidant.

Chemiluminescence Reaction of an Iron(III)-Phthalocyanine Complex and Its Application to FIA of L-Tyrosine

Chemiluminescence (CL) of a metal–phthalocyanine complex was studied, and an analytical application of CL detection-flow injection analysis (FIA) of L-tyrosine was developed. The CL reaction of iron (III)–phthalocyanine tetrasulfonic acid (Fe–PTS) was examined using eight metals (Cu, Fe, Ni, Co, Mg, Pd, Pt and Zn)–phthalocyanine complexes. The CL signal immediately appeared, when the Fe-PTS aqueous solution was injected into a hydrogen peroxide solution. Moreover, the influence of foreign substances on the CL system of Fe–PTS was examined. The decrease in the CL intensity of the iron–phthalocyanine complex was caused by adding a reducing agent such as L-tyrosine. The CL detection-FIA of trace amounts of L-tyrosine was then developed using this quenching phenomenon. The calibration curve was obtained in the concentration range 2.5 × 10 −7 M to 7.5 × 10 −6 M, and the sampling rate was 150 samples h −1 . Further, the relative standard deviation (RSD) was 1.20 % (n = 25) for 1.0 × 10 −6 M, and the detection limit (3σ) were 8.54 × 10 −8 M. The interference of metal ions was able to inhibit using EDTA. Therefore, the interference of L-cysteine was able to inhibit using Zn 2+ . As an application to a practical sample, L-tyrosine in a supplement was determined. The experimental value is almost the same as the tabulated one (1.0 × 10 −6 M) measured by amino acid autoanalyzer at the Japan Food Research Laboratories.

A Nitrido-bridged Heterometallic Ruthenium(IV)/Iron(IV) Phthalocyanine Complex Supported by A Tripodal Oxygen Ligand, [Co(η5-C5H5){P(O)(OEt)2}3]−: Synthesis, Structure, and Its Oxidation to Give Phthalocyanine Cation Radical and Hydroxyphthalocyanine Complexes

Dinuclear iron nitrido phthalocyanine complexes are of interest owing to their applications in catalytic oxidation of hydrocarbons. While nitrido-bridged diiron phthalocyanine complexes are well documented, the oxidation chemistry of heterodinuclear iron(IV) phthalocyanine nitrides has not been well explored. In this paper we report on the synthesis of a heterometallic FeIV/RuIV phthalocyanine nitride and its oxidation to yield phthalocyanine cation radical and hydroxyphthalocyanine complexes. Treatment of [FeII(Pc)] (Pc2- = phthalocyanine dianion) with [RuVI(LOEt)(N)Cl2] (LOEt- = [Co(η5-C5H5){P(O)(OEt)2}3]-) (1) afforded the heterometallic μ-nitrido complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(H2O)] (2) that contains an RuIV=N = FeIV linkage with the Ru-N and Fe-N distances of 1.689(6) and 1.677(6) Å, respectively, and Ru-N-Fe angle of 176.0(4)°. Substitution of 2 with 4- tert-butylpyridine (Bupy) gave [Cl2(LOEt)RuIV(μ-N)FeIV(Pc)(Bupy)]. The cyclic voltammogram of 2 displayed a reversible Pc-centered oxidation couple at +0.18 V versus Fc+/0 (Fc = ferrocene). The oxidation of 2 with [N(4-BrC6H4)3]SbCl6 led to isolation of the cationic complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)(H2O)][SbCl6]0.85[SbCl5(OH)]0.15 (2[SbCl6]0.85[SbCl5(OH)]0.15), whereas that with PhICl2 yielded the chloride complex [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)Cl] (3). Complexes 2[SbCl6]0.85[SbCl5(OH)]0.15 and 3 have been characterized by X-ray crystallography. The UV/visible spectra of 2+ (λmax = 515 and 747 nm) and 3 (λmax = 506 and 748 nm) displayed absorption bands that are characteristic of Pc cation radical. The EPR spectrum of 3 showed a signal with the g value of 2.0012 (width = 5 G) that is consistent with an organic radical. The spectroscopic data support the formulation of 2+ and 3 as RuIV-FeIV Pc cation radical complexes. The reaction of 2 with PhI(CF3CO2)2 in dried CH2Cl2 afforded a mixture of [Cl2(LOEt)RuIV(μ-N)FeIV(Pc·+)(CF3CO2)] (4) and a hydroxyphthalocyanine complex, [Cl2(LOEt)RuIV(μ-N)FeIV(Pc-OH)(H2O)](CF3CO2) (5), whereas that in wet CH2Cl2 (containing ca. 0.5% water) led to isolation of 5 as the sole product. Complex 4 was independently prepared by salt metathesis of 3 with AgCF3CO2.

Conversion of Olefins into Ketones by an Iron‐Catalyzed Wacker‐type Oxidation Using Oxygen as the Sole Oxidant

AbstractWe describe a mild and operationally simple procedure for the oxidation of olefins into ketones. The reaction is catalyzed by the hexadecafluorinated iron–phthalocyanine complex FePcF16 with stoichiometric amounts of triethylsilane as an additive under oxygen atmosphere to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Ketone formation proceeds in up to 95 % yield and with 100 % regioselectivity while the corresponding alcohols were observed as side products.

Conversion of Olefins into Ketones by an Iron-Catalyzed Wacker-type Oxidation Using Oxygen as the Sole Oxidant.

We describe a mild and operationally simple procedure for the oxidation of olefins into ketones. The reaction is catalyzed by the hexadecafluorinated iron-phthalocyanine complex FePcF16 with stoichiometric amounts of triethylsilane as an additive under oxygen atmosphere to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Ketone formation proceeds in up to 95 % yield and with 100 % regioselectivity while the corresponding alcohols were observed as side products.

Insight into the reactivity difference of two iron phthalocyanine catalysts in chromogenic reaction: DFT theoretical study

ABSTRACTChromogenic reaction catalyzed by metal phthalocyanine (MPc) complexes is a novel and practical method for the facile identification of phenolic pollutants. Exploring the catalytic reaction mechanism is the current concern in the investigation. In this work, tetranitro iron (II) phthalocyanine (TNFe(II)Pc) and iron (II) phthalocyanine (Fe(II)Pc) catalyzed chromogenic reactions were studied at the B3LYP level on the basis of the density functional theory (DFT) calculation. The molecular structure, atomic charge, and frontier molecular orbital of these two kinds of iron phthalocyanine complex were investigated. The calculation results demonstrate that no obvious difference for geometry structures of Fe(II)Pc and TNFe(II)Pc macrocycle can be found, while the atomic charge of Fe atom increases obviously with the four nitro groups substituted on the peripheral of macrocycle. By applying the descriptor of donor–acceptor molecular hardness, the difference of electron transfer from chlorophenol substrates to TNFe(II)Pc/Fe(II)Pc was well explained. Our investigations could provide a new strategy in designing various MPc catalysts for chromogenic identification of chlorophenol pollutants.

Non-Precious Metal Catalyst That Combines Perovskite-Type Oxide and Iron Phthalocyanine for Use as a Cathode Catalyst in an Alkaline Fuel Cell

A non-precious metal catalyst was obtained by combining a perovskite-type oxide-carbon mixture (La0.6Sr0.4MnO3/C, La0.6Sr0.4CoO3/C, and La0.6Sr0.4Mn0.7Co0.3O3/C) and an iron phthalocyanine complex (Fe-Pc) with two-by-two electron O2 reduction activity. The oxygen reduction reaction (ORR) activities of the Fe-Pc/perovskite/C catalysts were investigated in alkaline media using rotating ring-disk electrode (RRDE) method. Although all of the Fe-Pc/perovskite/C catalysts showed enhanced ORR activities with a positive shift of the onset potential compared to perovskite/C and Fe-Pc/C, the number of electrons during ORR was different due to the HO2− reduction activity of the perovskite/C. Among the prepared catalysts, the Fe-Pc/La0.6Sr0.4Mn0.7Co0.3O3/C catalyst exhibited the highest catalytic activity, which was comparable to that of the Pt/C catalyst. Furthermore, oxygen reduction on this catalyst proceeds thorough an efficient 2+2 pathway with the formation of only a very small fraction of HO2− (0.5–3%).

A Mild Catalytic Oxidation System: FePcOTf/H2O2 Applied for Cyclohexene Dihydroxylation.

Iron (III) phthalocyanine complexes were employed for the first time as a mild and efficient Lewis acid catalyst in the selective oxidation of cyclohexene to cyclohexane-1,2-diol. It was found that the catalyst FePcOTf shown excellent conversion and moderate selectivity relative to other iron (III) phthalocyanine complexes. The optimum conditions of the oxidation reaction catalyzed by FePcOTf/H2O2 have been researched in this paper. Iron (III) phthalocyanine triflate (1 mol %) as catalyst, hydrogen peroxide as oxidant, methanol as solvent, and a mole ratio of substrate and oxidant (H2O2) of 1:1 were used for achieving moderate yields of 1,2-diols under reflux conditions after eight hours.

Co(II) and Fe(II) phthalocyanines: synthesis, investigation of their catalytic activity towards phenolic compounds and electrochemical behaviour

4‐[(1‐Benzylpiperidin‐4‐yl)oxy]‐substituted cobalt(II) and iron(II) phthalocyanine complexes were synthesized and their catalytic activity towards various phenolic compounds was investigated. Converting from environmentally harmful phenolic compounds into less harmful oxidation products using phthalocyanines makes this study attractive. This catalysis is feasible and time‐saving in terms of procedure and the best oxidation conditions determined. Electrochemical studies were also carried out using cyclic voltammetry and square wave voltammetry techniques. Voltammetric analyses of the synthesized phthalocyanine complexes supported their proposed structures. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Direct Synthesis of 1,4‐Diols from Alkenes by Iron‐Catalyzed Aerobic Hydration and CH Hydroxylation

AbstractVarious 1,4‐diols are easily accessible from alkenes through iron‐catalyzed aerobic hydration. The reaction system consists of a user‐friendly iron phthalocyanine complex, sodium borohydride, and molecular oxygen. Furthermore, the effect of additional ligands on the iron complex was examined for a model reaction. The second hydroxy group is installed by direct C(sp3)H oxygenation, which is based on a [1,5] hydrogen shift process of a transient alkoxy radical that is formed by formal hydration of the olefin.

Direct Synthesis of 1,4‐Diols from Alkenes by Iron‐Catalyzed Aerobic Hydration and CH Hydroxylation

Various 1,4-diols are easily accessible from alkenes through iron-catalyzed aerobic hydration. The reaction system consists of a user-friendly iron phthalocyanine complex, sodium borohydride, and molecular oxygen. Furthermore, the effect of additional ligands on the iron complex was examined for a model reaction. The second hydroxy group is installed by direct C(sp(3))-H oxygenation, which is based on a [1,5] hydrogen shift process of a transient alkoxy radical that is formed by formal hydration of the olefin.