Molecular layers of ZnPc and FePc on Au(111) surface: Charge transfer and chemical interaction

We have studied zinc phthalocyanine (ZnPc) and iron phthalocyanine (FePc) thick films and monolayers on Au(111) using photoelectron spectroscopy and x-ray absorption spectroscopy. Both molecules are adsorbed flat on the surface at monolayer. ZnPc keeps this orientation in all investigated coverages, whereas FePc molecules stand up in the thick film. The stronger inter-molecular interaction of FePc molecules leads to change of orientation, as well as higher conductivity in FePc layer in comparison with ZnPc, which is reflected in thickness-dependent differences in core-level shifts. Work function changes indicate that both molecules donate charge to Au; through the π-system. However, the Fe3d derived lowest unoccupied molecular orbital receives charge from the substrate when forming an interface state at the Fermi level. Thus, the central atom plays an important role in mediating the charge, but the charge transfer as a whole is a balance between the two different charge transfer channels; π-system and the central atom.     

Potassium induced phase transition of FePc thin films

We have studied the structure and stoichiometry of potassium doped iron phthalocyanine (FePc) films using a combination of electron diffraction and core level excitation studies. We show that iron phthalocyanine undergoes structural phase transitions upon potassium addition, which can be described by the formation of two potassium doped phases with K2FePc and K4FePc composition.     

FePc结构对Pd(OAc)2/HQ/FePc催化环己烯氧化活性的影响

在乙腈酸性水溶液中,不同来源酞菁铁(FePc)和Pd(OAc)2/HQ（氢醌）组成的催化体系在环己烯氧化反应中有明显不同的催化活性.通过IR、Mssbauer、XPS、XRD、SEM、BET等技术对酞菁铁的分析表明,由酞菁铁组成的多组份催化体系的催化活性与酞菁铁中的飒 氧酞菁铁含量、酞菁铁结晶度和表面形态有关.     

FePc结构对Pd(OAc)_2/HQ/FePc催化环己烯氧化活性的影响

在乙腈酸性水溶液中 ,不同来源酞菁铁 (FePc)和 Pd(OAc)2/HQ(氢醌)组成的催化体系在环己烯氧化反应中有明显不同的催化活性 .通过 IR、 M ssbauer、 XPS、 XRD、 SEM、 BET等技术对酞菁铁的分析表明 ,由酞菁铁组成的多组份催化体系的催化活性与酞菁铁中的μ 氧酞菁铁含量、酞菁铁结晶度和表面形态有关 .     

Densely packed overlayer of iron phthalocyanine molecules grown on single-layer graphene

The FePc molecules form a series of order superstructures on single-layer graphene grown on Ru(0001) with increasing molecular coverage.     

Enhanced catalytic activity of Fe phthalocyanines linked to Au(111) via conjugated self-assembled monolayers of aromatic thiols for O2 reduction

We have obtained and characterized self assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (FePc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/FePc was examined for the reduction of O₂ in aqueous media (pH = 4) and compared with that of bare gold and of gold coated directly with FePc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by FePc. The electrocatalytic studies carried out with Au/FePc, Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O₂ reduction takes place by a 4-electron transfer to give water in contrast to a 2-electron-transfer process observed on the bare gold. The activity of the electrodes increases as follows: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc.     

Ammonia adsorption on iron phthalocyanine on Au(111): influence on adsorbate-substrate coupling and molecular spin

The adsorption of ammonia on Au(111)-supported monolayers of iron phthalocyanine has been investigated by x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory calculations. The ammonia-induced changes of the x-ray photoemission lines show that a dative bond is formed between ammonia and the iron center of the phthalocyanine molecules, and that the local spin on the iron atom is quenched. This is confirmed by density functional theory, which also shows that the bond between the iron center of the metalorganic complex and the Au(111) substrate is weakened upon adsorption of ammonia. The experimental results further show that additional adsorption sites exist for ammonia on the iron phthalocyanine monolayer.     

Dynamics of analyte binding onto a metallophthalocyanine: NO/FePc

The gas-surface reaction dynamics of NO impinging on an iron(II) phthalocyanine (FePc) monolayer were investigated using King and Wells sticking measurements. The initial sticking probability was measured as a function of both incident molecular beam energy (0.09-0.4 eV) and surface temperature (100-300 K). NO adsorption onto FePc saturates at 3% of a monolayer for all incident beam energies and surface temperatures, suggesting that the final chemisorption site is confined to the Fe metal centers. At low surface temperature and low incident beam energy, the initial sticking probability is 40% and decreases linearly with increasing beam energy and surface temperature. The results are consistent with the NO molecule sticking onto the FePc molecules via physisorption to the aromatics followed by diffusion to the Fe metal center, or precursor-mediated chemisorption. The adsorption mechanism of NO onto FePc was confirmed by control studies of NO sticking onto metal-free H2Pc, inert Au111, and reactive Al111.     

Effects of iron phthalocyanine on the inner pressure of MH/Ni battery

The inner gas pressure of the battery beyond 1.01 106 Pa can cause a release of gas from the safety valve for a normal sealed cell, leading to a drying out of electrolyte solution[1], and gradually decreasing the performance of the battery until finally destroying it. During overcharging, oxygen is produced rapidly on the nickel electrode, and it is necessary to eliminate the oxygen and restrain the rising speed of inner pres-sure so as to improve the performance of MH/Ni bat-tery. Phthalocy…     

On-Surface Synthesis of Iron Phthalocyanine Using Metal-Organic Coordination Templates

On-surface synthesis provides a convenient route to many kinds of conjugated molecular nanostructures, but it has remained challenging to precisely control the reaction pathway for using multicomponent precursors. Herein, we demonstrate a two-step strategy to synthesize iron phthalocyanine (FePc) molecules using metal-organic coordination for templating by using high-resolution scanning tunnelling microscopy and non-contact atomic force microscopy. In a first step, 1,2,4,5-tetracyanobenzene (TCNB) precursors and Fe atoms self-assembly into Fe(TCNB)₄ coordination complexes on a clean Au(111) surface. The Fe(TCNB)₄ complexes further undergo cyclic tetramerization upon thermal annealing, forming single FePc molecules. We expect that our demonstrated synthetic strategy may shed light on the design and synthesis of two-dimensional extended conjugated systems.     

Synthesis,thermal stability and structural characterisation of iron(II) phthalocyanine complex with 4-cyanopyridine

A new complex of bis-axially coordinated iron(II) phthalocyanine by 4-cyanopyridine (4-CNpy) has been obtained in crystalline form as an adduct with two 4-CNpy molecules. The [FePc(4-CNpy)₂] · 2(4-CNpy) crystallises in the monoclinic system, space group P2₁/c with two molecules in the unit cell. The iron(II) coordinates four isoindole nitrogen atoms of the almost planar phthalocyaninato(2−) macroring and axially two nitrogen atoms of 4-CNpy molecules. The coordination polyhedron around the Fe(II) atom approximates to a tetragonal by-pyramid. Four equatorial Fe–N bonds are shorter (1.936(2) Å) than two axial Fe–N bonds (2.027(2) Å). The centrosymmetric FePc(4-CNpy)₂ molecules form alternating sheets parallel to the bc crystallographic plane and solvated 4-CNpy molecules that are anti-parallel oriented by their polar cyano groups are located between the sheets of FePc(4-CNpy)₂ molecules. Ligation of the intermediate-spin iron(II) phthalocyanine by 4-CNpy molecules leads to the low spin Fe(II) complex. The importance of the d(π) → π^∗(Pc) back donation is manifested in the difference between the values of C–N isoindole and C–N azamethine bond lengths of the Pc macrocycle. The thermal analysis of the crystals of [FePc(4-CN)₂] · 2(4-CNpy) shows two steps responsible for a loss of solvated (∼170 °C) and coordinated (∼235 °C) 4-CNpy molecules.     

Molecular interface effect of heterogeneous molecular junctions consisting of nonfluorinated and fluorinated phthalocyanines

We report the tunneling behavior of homogeneous and heterogeneous molecular junctions using p-type molecules of iron phthalocyanine (FePc), phthalocyanine (H(2)Pc), and copper(II) octaalkoxyl substituted phthalocyanine (CuPcOC8) and n-type molecule of copper hexadecafluorophthalocyanine (F(16)CuPc). The molecular films formed on the electrode surfaces were inspected by X-ray photoelectron spectroscopy (XPS). The measured characteristic tunneling curves of single-component phthalocyanines revealed comparable energy gaps for homogeneous tunneling junctions using the photoemission method. In contrast, for the heterogeneous tunnel junctions of mixed phthalocyanines including fluorinated phthalocyanine a distinctive offset of the energy gaps to the positive bias voltage direction can be clearly identified. It is suggested that the substitution of phthalocyanines and surface affinity of phthalocyanines could contribute to the controlled phase separation within the heterogeneous tunneling junctions. The apparent shift of the tunneling spectra is attributed to the existence of an internal electric field originated with the phase separation of the binary mixture of p-type and n-type phthalocyanines within the tunneling junction.     

A density functional theory study on the binding of NO onto FePc films

To develop an atomistic understanding of the binding of NO with iron phthalocyanine (FePc), the interaction between NO (an electron withdrawing gas) and NH3 (an electron donating gas) with an isolated FePc molecule (monomer) was compared with density functional theory. The simulations show that NO strongly chemisorbs to the Fe metal and physisorbs to all the nonmetal sites. Additionally, when NO physisorbs to the inner ring nitrogens, NO subsequently undergoes a barrierless migration to the deep chemisorption well on the Fe metal. Conversely, NH3 only weakly chemisorbs to the Fe metal and does not bind to any other sites. Projected density of states simulations and analysis of the atomic charges show that the binding of NO to the FePc metal results in a charge transfer from the Fe metal to the NO chemisorbate; the opposite effect is observed for the binding of NH3 to the Fe metal. Simulations of NO binding to the Fe metal of a monolayer FePc film and FePc trimer were also performed to show that intermolecular FePc-FePc interactions have a negligible effect on the FePc electronic structure and NO binding.     

Exploiting distinct molecular architectures of ultrathin films made with iron phthalocyanine for sensing

The possibility of generating distinct film properties from the same material is crucial for a number of applications, which can only be achieved by controlling the molecular architecture. In this paper we demonstrate as a proof-of-principle that ultrathin films produced from iron phthalocyanine (FePc) may be used to detect trace amounts of copper ions in water, where advantage was taken of the cross sensitivity of the sensing units that displayed distinct electrical properties. The ultrathin films were fabricated with three methods, namely physical vapor deposition (PVD), Langmuir-Blodgett (LB), and electrostatic layer-by-layer (LbL) techniques, where for the latter tetrasulfonated phthalocyanine was used (FeTsPc). PVD and LB films were more homogeneous than the LbL films at both microscopic and nanoscopic scales, according to results from micro-Raman spectroscopy and atomic force microscopy (AFM), respectively. From FTIR spectroscopy data, these more homogeneous films were found to have FePc molecules oriented preferentially, tilted in relation to the substrate surface, while FeTsPc molecules were isotropically distributed in the LbL films. Impedance spectroscopy measurements with films adsorbed onto interdigitated gold electrodes indicated that the electrical response depends on the type of film-forming method and varies with incorporation of copper ions in aqueous solutions. Using principal component analysis (PCA), we were able to exploit the cross sensitivity of the sensing units and detect copper ions (Cu(2+)) down to 0.2 mg/L, not only in ultrapure water but also in distilled and tap water. This level of sensitivity is sufficient for quality control of water for human consumption, with a fast, low-cost method.     

Does CO poison Fe-based catalysts for ORR?

Catalysts for the oxygen reduction reaction (ORR) were prepared on carbon black (C) using Fe^IIphthalocyanine (FePc) and Cl–Fe^IIItetramethoxyphenylporphyrin (ClFeTMPP), as Fe precursors with and without a pyrolysis step at 800 °C. CO poisoning of the ORR catalytic sites for all these Fe/N/C electrocatalysts was attempted at pH 1 and 13, but to no avail, even if an iron ion is known to occupy the center of the active sites in at least the unpyrolyzed FePc/C or ClFeTMPP/C. The exact nature of the active center of these Fe-based heat-treated catalysts may still be a subject of debate but, in light of the absence of CO poisoning for unpyrolyzed FePc/C and ClFeTMPP/C, resistance to CO poisoning by the heat-treated catalysts cannot be used as evidence that the active center of their catalytic site is devoid of iron.     

The role of iron(II) phthalocyanine as a catalyst in Wacker oxidation of 1-decene

The Wacker oxidation of 1-decene to 2-decanone by dioxygen catalyzed by Pd(OAc)₂, hydroquinone and iron(II) phthalocyanine (FePc) in acidic aqueous dimethylformamide gives high yield m 40 min at room temperature. The major factors controlling the activity of the multi-component catalyst are the structure and morphology of the FePc, which were analyzed by IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and BET surface area measurement. The dimeric μ-oxo(1) form of FePc is highly active, has higher surface area, and is less crystalline than the inactive monomeric β-FePc. The rate of oxidation using the most active catalyst is limited by the solubility of 1-decene in aqueous DMF.     

Distribution and structure of N atoms in multiwalled carbon nanotubes using variable-energy X-ray photoelectron spectroscopy

We investigated the inhomogeneous distribution of concentration and electronic structure of the nitrogen (N) atoms doped in the multiwalled carbon nanotubes (CNTs) by variable-energy X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure, and electron energy-loss spectroscopy. The vertically aligned N-doped CNTs on the substrates were grown via pyrolysis of iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), and nickel phthalocyanine (NiPc) in the temperature range 750-1000 degrees C. They usually have a bamboo-like structure, and the diameter is in the range of 15-80 nm. As the photon energy of XPS increases from 475 to 1265 eV, the N content increases up to 8 atomic %, indicating a higher N concentration at the inside of nanotubes. We identified three typed N structures: graphite-like, pyridine-like, and molecular N(2). The pyridine-like N structure becomes significant at the inner walls. Molecular N(2) would exist as intercalated forms in the vicinity of hollow inside. The XPS valence band analysis reveals that the pyridine-like N structure induces the metallic behaviors. The CNTs grown using NiPc contain the higher content of pyridine-like structure compared to those grown using FePc and CoPc, so they exhibit more metallic properties.     

Mössbauer and ESR study of pyridine-inactive phthalocyanineiron (II) in zeolite supercage

Pyridine-treated phthalocyanineiron (II) (FePc) was synthesized in a NaY-zeolite supercage. Mössbauer spectra indicated the presence of pyridine-inactive FePc without any change of Mössbauer parameters. The relative yield of the inactive complex was not simply dependent on the amount of iron doped and the temperature during reduction for preparation. Spin-spin interaction may have broadened the ESR signal at g=6 for FePc in zeolite, suggesting that the FePc molecules are located close together in zeolite. It is postulated that two types of FePc in zeolite particle were formed, in accordance with the reactivity of FePc to pyridine adduct formation.     

Weak epitaxy growth and phase behavior of planar phthalocyanines on p-sexiphenyl monolayer film

We systematically investigated the weak epitaxy growth (WEG) behavior of a series of planar phthalocyanine compounds (MPc), i.e., metal-free phthalocyanine (H2Pc), nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), grown on a p-sexiphenyl ( p-6P) monolayer film by selected area electron diffraction (SAED) and atomic force microscopy (AFM). Two types of epitaxial relations, named as incommensurate epitaxy and commensurate epitaxy, were identified between phthalocyanine compounds and the substrate of the p-6P film. The tiny variation of the lattice constant of phthalocyanine compounds can result in different crystal orientations. The change rule of incommensurate and commensurate epitaxy was extracted. The tendency of commensurate epitaxy becomes weaker as the lattice constant b increases, while it gets stronger as the substrate temperature is elevated. Large size and continuous H2Pc films can be obtained by controlling the growth conditions. The WEG method is generally applicable in the whole family of planar phthalocyanine compounds and may be used to fabricate other high-quality organic films.