Properties of copper (fluoro-)phthalocyanine layers deposited on epitaxial graphene

We investigate the atomic structure and electronic properties of monolayers of copper phthalocyanines (CuPc) deposited on epitaxial graphene substrate. We focus in particular on hexadecafluorophthalocyanine (F(16)CuPc), using both theoretical and experimental (scanning tunneling microscopy - STM) studies. For the individual CuPc and F(16)CuPc molecules, we calculated the electronic and optical properties using density functional theory (DFT) and time-dependent DFT and found a red-shift in the absorption peaks of F(16)CuPc relative to those of CuPc. In F(16)CuPc, the electronic wavefunctions are more polarized toward the electronegative fluorine atoms and away from the Cu atom at the center of the molecule. When adsorbed on graphene, the molecules lie flat and form closely packed patterns: F(16)CuPc forms a hexagonal pattern with two well-ordered alternating α and β stripes while CuPc arranges into a square lattice. The competition between molecule-substrate and intermolecular van der Waals interactions plays a crucial role in establishing the molecular patterns leading to tunable electron transfer from graphene to the molecules. This transfer is controlled by the layer thickness of, or the applied voltage on, epitaxial graphene resulting in selective F(16)CuPc adsorption, as observed in STM experiments. In addition, phthalocyanine adsorption modifies the electronic structure of the underlying graphene substrate introducing intensity smoothing in the range of 2-3 eV below the Dirac point (E(D)) and a small peak in the density of states at ～0.4 eV above E(D).     

酞菁和酞菁铜的三阶非线性光学性质

用INDO/SDCI方法研究了酞菁和酞菁铜的电子结构, 紫外-可见光谱, 三阶非线性光学系数及其色散效应, 发现酞菁铜中Cu^2+对γ的贡献很小, 故酞菁与酞菁铜的γ几乎相等, 我们的计算结果对此进行了合理的解释。     

The electronic properties of potassium doped copper-phthalocyanine studied by electron energy-loss spectroscopy

The authors have studied the electronic structure of potassium doped copper-phthalocyanine using electron energy-loss spectroscopy. The evolution of the loss function indicates the formation of distinct KxCuPc phases. Taking into account the C1s and K2p core level excitations and recent results by Giovanelli et al. [J. Chem. Phys. 126, 044709 (2007)], they conclude that these are K2CuPc and K4CuPc. They discuss the changes in the electronic excitations upon doping on the basis of the molecular electronic levels and the presence of electronic correlations.     

Electronic structure of copper phthalocyanine: a comparative density functional theory study

We present a systematic density functional theory study of the electronic structure of copper phthalocyanine (CuPc) using several different (semi)local and hybrid functionals and compare the results to experimental photoemission data. We show that semilocal functionals fail qualitatively for CuPc primarily because of underbinding of localized orbitals due to self-interaction errors. We discuss an appropriate choice of functional for studies of CuPc/metal interfaces and suggest the Heyd-Scuseria-Ernzerhof screened hybrid functional as a suitable compromise functional.     

酞菁铜分子的电子态和反饱和吸收

用ROHF-INDO/SDCI方法结合实验研究了酞菁铜分子的电子的电子结构.紫外-可见光谱.激发态分子动态学和反饱和吸收的微观机制.对酞菁铜实现反饱和吸收的必要条件是最低四重态对激光的吸收截面必须大于基态对激光的吸收截面. 在波长为532nm的激光作用下.该条件得到了满足,故Cupc呈现反饱和吸收特征.理论分析与实验结果一致.     

The Crystalline Structure of Copper Phthalocyanine Films on ZnO(11̅00)

The structure of copper phthalocyanine (CuPc) thin films (5-100 nm) deposited on single-crystal ZnO(11?00) substrates by organic molecular beam deposition was determined from grazing-incidence X-ray diffraction reciprocal space maps. The crystal structure was identified as the metastable polymorph α-CuPc, but the molecular stacking was found to vary depending on the film thickness: for thin films, a herringbone arrangement was observed, whereas for films thicker than 10 nm, coexistence of both the herringbone and brickstone arrangements was found. We propose a modified structure for the herringbone phase with a larger monoclinic β angle, which leads to intrastack Cu-Cu distances closer to those in the brickstone phase. This structural basis enables an understanding of the functional properties (e.g., light absorption and charge transport) of (opto)electronic devices fabricated from CuPc/ZnO hybrid systems.     

Matrix effects on copper(II)phthalocyanine complexes. A combined continuous wave and pulse EPR and DFT study

The effect of the electron withdrawing or donating character of groups located at the periphery of the phthalocyanine ligand, as well as the influence of polar and nonpolar solvents are of importance for the redox chemistry of metal phthalocyanines. Continuous wave and pulse electron paramagnetic resonance and pulse electron nuclear double resonance spectroscopy at X- and Q-band are applied to investigate the electronic structure of the complexes Cu(II)phthalocyanine (CuPc), copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc(t)), and copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (CuPc(F)) in various matrices. Isotope substitutions are used to determine the g values, the copper hyperfine couplings and the hyperfine interactions with the 14N, 1H and 19F nuclei of the macrocycle and the surrounding matrix molecules. Simulations and interpretations of the spectra are shown and discussed, and a qualitative analysis of the data using previous theoretical models is given. Density functional computations facilitate the interpretation of the EPR parameters. The experimental g, copper and nitrogen hyperfine and nuclear quadrupole values are found to be sensitive to changes of the solvent and the structure of the macrocycle. To elucidate the electronic, structural and bonding properties the changes in the g principal values are related to data from UV/Vis spectroscopy and to density functional theory (DFT) computations. The analysis of the EPR data indicates that the in-plane metal-ligand sigma bonding is more covalent for CuPc(t) in toluene than in sulfuric acid. Furthermore, the out-of-plane pi bonding is found to be less covalent in the case of a polar sulfuric acid environment than with nonpolar toluene or H2Pc environment, whereby the covalency of this bonding is increased upon addition of tert-butyl groups. No contribution from in-plane pi bonding is found.     

The Origin of the Halogen Effect on the Phthalocyanine Green Pigments

The structure and the electronic and optical properties of halogenated copper‐phthalocyanine (nα,mβ(Hal)‐CuPc) molecules are investigated, according to the variation in the substituted halogen‐atom species (Hal=Cl or Br) at the α and β positions of isoindole ring with different numbers (n and m=0, 4, 8, or 16). Our results show that the halogen effect mainly results from a structural deformation rather than caused by electronic effects. A nonplanar deformation of the phthalocyanine chromophore of the nα,mβ(Hal)‐CuPc molecule causes a significant change only in the HOMO and HOMO‐1 levels, rather than in the LUMO levels, which leads to the appearance of a green color arising from the large red‐shifts of the Soret and Q bands. The present result may serve as an important reference point for designing novel halogen‐free green pigments, in accordance with the environmental regulations for the restriction of hazardous substances (RoHS) in electronic and electrical devices.     

Electronic structure of crystalline copper phthalocyanine

The electronic structure of copper-phthalocyanine (CuPc) has been studied both experimentally and theoretically. Experiments have been performed on alpha and beta crystalline phases, using photoemission spectroscopy to probe core levels and valence band spectra. Different photon energies have been used, in order to probe different sample depths. Only minor differences have been observed in the experimental data on the two different phases, except for a small charge effect on the beta phase crystal. First-principles calculations have been performed using the density functional for molecular and three-dimensional periodic solids (Dmol(3)) code on both the single CuPc molecule and the beta phase, allowing the identification of the different atomic and angular contributions to the experimental density of states. In particular, the highest occupied molecular level is mainly due to Cu and N states. The comparison between theoretical data obtained for the CuPc in the beta phase and in the single molecule shows that the interchain interaction between the molecules is negligible, whereas slightly stronger intrachain interactions occur.     

Quantum transport effects in copper(II) phthalocyanine sandwiched between gold nanoelectrodes

The electrical transmission of copper(II) phthalocyanine (CuPc) sandwiched between gold nanoelectrodes is studied on the basis of the Green function formalism coupled with the Gaussian-broadening technique. In the Au-CuPc-Au junction, broadened density of states (DOS) of the Au chains is defined as continuous DOS of electrodes to calculate the Green function of the electrodes. Two peaks of the transmission function found in the vicinity of the Fermi level are analyzed in terms of molecular orbitals (MOs). A convenient procedure to analyze MO contribution to a transmission peak is proposed. It is found that (I) symmetry-matched interactions between CuPc and the gold nanoelectrodes are important to the enhancement of the transmission function and (II) the nanoelectrodes have almost no effect on the electronic states of CuPc.     

高比表面积CuPc/TiO2纳米管复合材料的制备及其可见光光催化活性

以P25为前驱体,在碱性条件下采用水热法制备了TiO2纳米管(NT),然后通过浸渍法将敏化剂酞菁铜(CuPc)附着于TiO2NT表面,制得可见光响应的CuPc/TiO2NT复合光催化材料,并对其进行了表征,考察了它在可见光下降解罗丹明B的光催化活性.结果表明,在NaOH碱性条件下水热法制备的TiO2NT具有较大的比表面...     

Thickness-dependent structural transitions in fluorinated copper-phthalocyanine (F16CuPc) films

The detailed structure of F16CuPc films on SiO2 has been determined by means of in situ grazing incidence X-ray diffraction from the first monolayer to thicker films. In contrast to films of the homologous H16CuPc molecule, the F16CuPc films exhibit the same structure independently from the deposition temperature. The films show a thickness-dependent polymorphism manifested in the in-plane crystal structure, which implies large differences in the molecular tilt within the cofacial stacking of the molecules.     

Circuit simulation for the dielectric responses of the composites of copper phthalocyanine oligomers and sulfonated polyurethanes by separating the structural elements

The copper phthalocyanine (CuPc) oligomer with high dielectric constant was synthesized by the solution method. The FT‐IR and X‐ray diffraction results revealed its chemical structure. The high dielectric constant of CuPc was proved to result from the free movement of charge carriers along the conjugated orbitals. The composites of CuPc and sulfonated polyurethane (PUI) were prepared and the contents of CuPc in the composites were varied from 10 to 50 wt %. The dielectric performance was greatly enhanced for the composite compared with that of average polymers. Different from the behaviors appeared in a common composite with conductive fillers, there is no percolation phenomenon observed in the CuPc/PUI composite, and the dielectric constants of CuPc/PUI composites decreased with the increase in the CuPc content, which is assumed to due to the strong electrostatic interactions between CuPc and PUI. Considering the many‐body interactions within the bulk sample and the contact effect between the bulk sample and the metallic electrode, an equivalent circuit was established to simulate the dielectric behaviors of the composites and computational curve fitting was done. The results were in good agreement, indicating that the dielectric responses of the composites come from both the extrinsic and the intrinsic contributions. The extrinsic was associated with the Maxwell‐Wagner relaxation at the interface between the electrode and the bulk sample, and the intrinsic was associated with the huge dipoles provided by the mobile charges within the CuPc grains and the interaction among them in the bulk composites. A circuit model concerning the universal dielectric response was proposed in describing the intrinsic contribution, which quantitatively verified the strong interaction among the dipoles with the relaxation time, representing the aggregated structure of CuPc when its content was high in the composites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1146–1155, 2009     

Correlation between molecular orbitals and doping dependence of the electrical conductivity in electron-doped metal-phthalocyanine compounds

We have performed a comparative study of the electronic properties of six different electron-doped metal-phthalocyanine (MPc) compounds (ZnPc, CuPc, NiPc, CoPc, FePc, and MnPc), in which the electron density is controlled by means of potassium intercalation. Despite the complexity of these systems, we find that the nature of the underlying molecular orbitals produces observable effects in the doping dependence of the electrical conductivity of the materials. For all the MPc's in which the added electrons are expected to occupy orbitals centered on the ligands (ZnPc, CuPc, and NiPc), the doping dependence of the conductivity has an essentially identical shape. This shape is different from that observed in MPc materials in which electrons are also added to orbitals centered on the metal atom (CoPc, FePc, and MnPc). The observed relation between the macroscopic electronic properties of the MPc compounds and the properties of the molecular orbitals of the constituent molecules clearly indicates the richness of the alkali-doped metal-phthalocyanines as a model class of compounds for the investigation of the electronic properties of molecular systems.     

Characterization of the interface interaction of cobalt on top of copper- and iron-phthalocyanine

The electronic structure of the interface between ferromagnetic cobalt and the organic semiconductors copper- (CuPc) and iron-phthalocyanine (FePc) was investigated by means of photoemission spectroscopy (UPS, IPES, and XPS). These metal-phthalocyanine (MePc) molecules have an open shell structure and are known to show promising properties for their use in organic spintronics. In spintronic devices, the interface between ferromagnetic electrode and the organic layer determines the spin injection properties and is hence important for the quality of, e.g., a possible spin-valve device. For this purpose, cobalt was deposited onto the MePcs, such as in devices with ferromagnetic top contacts. The reported investigations reveal a diffusion of cobalt into the organic layers and chemical reactions at the interface.     

Phthalocyanine and polystyrene film nanocomposites

The organic solvent was shown to determine the structure of copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) in the CuPc-polystyrene composite during the formation of the latter. The structure and morphology of the resulting nanocomposite films was studied by atomic force and transmission electron microscopy. Different physical structures of CuPc formed in different solvents (cyclohexane, toluene, chloroform, and trichloroethylene).     

Electronic structure of copper phthalocyanine: an experimental and theoretical study of occupied and unoccupied levels

An experimental and theoretical study of the electronic structure of copper phthalocyanine (CuPc) molecule is presented. We performed x-ray photoemission spectroscopy (XPS) and photoabsorption [x-ray absorption near-edge structure (XANES)] gas phase experiments and we compared the results with self-consistent field, density functional theory (DFT), and static-exchange theoretical calculations. In addition, ultraviolet photoelectron spectra (UPS) allowed disentangling several outer molecular orbitals. A detailed study of the two highest occupied orbitals (having a(1u) and b(1g) symmetries) is presented: the high energy resolution available for UPS measurements allowed resolving an extra feature assigned to vibrational stretching in the pyrrole rings. This observation, together with the computed DFT electron density distributions of the outer valence orbitals, suggests that the a(1u) orbital (the highest occupied molecular orbital) is mainly localized on the carbon atoms of pyrrole rings and it is doubly occupied, while the b(1g) orbital, singly occupied, is mainly localized on the Cu atom. Ab initio calculations of XPS and XANES spectra at carbon K edge of CuPc are also presented. The comparison between experiment and theory revealed that, in spite of being formally not equivalent, carbon atoms of the benzene rings experience a similar electronic environment. Carbon K-edge absorption spectra were interpreted in terms of different contributions coming from chemically shifted C 1s orbitals of the nonequivalent carbon atoms on the inner ring of the molecule formed by the sequence of CN bonds and on the benzene rings, respectively, and also in terms of different electronic distributions of the excited lowest unoccupied molecular orbital (LUMO) and LUMO+1. In particular, the degenerate LUMO appears to be mostly localized on the inner pyrrole ring.     

八羧基铜酞菁修饰海藻酸钠阳膜层制备CuPc(COOH)8-SA/mCS双极膜及其表征

在海藻酸钠(SA)中添加八羧基铜酞菁(CuPc(COOH)₈),并分别用Fe³⁺离子和戊二醛作为交联剂对海藻酸钠-八羧基铜酞菁阳膜层和壳聚糖(CS)阴膜层进行改性,制备了八羧基铜酞菁-海藻酸钠/改性壳聚糖双极膜(CuPc(COOH)₈-SA/mCS BPM)。在海藻酸钠中添加八羧基铜酞菁以促进中间层中水的解离。用FTIR、SEM等对制备的CuPc(COOH)₈-SA/mCS双极膜进行了表征。作为比对,制备了Fe³⁺离子改性的Fe-SA/mCS双极膜和二茂铁(Fc)离子改性的Fc-SA/mCS双极膜。实验结果表明,CuPc(COOH)₈-SA阳离子交换膜的离子交换容量、H⁺离子透过率均获得提高。与Fe³⁺离子改性或二茂铁离子改性的mSA/mCS双极膜相比,CuPc(COOH)₈-SA/mCS双极膜的阻抗、电阻压降(IR降)和溶胀度降低,在H+离子浓度低于8 mol·L^-1的酸溶液中具有稳定的工作性能。     

Supramolecular Assembly of a 2D Binary Network of Pentacene and Phthalocyanine on Cu(100)

A crystalline nanoporous molecular network was tailored by supramolecular assembly of pentacene and F₁₆CuPc on Cu(100). The structure and self‐assembly mechanisms of the pure and binary layers were analyzed by STM. F₁₆CuPc films and mixed layers of pentacene/F₁₆CuPc in a ratio of 2:1 show two enantiomorphic chiral domains with high structural order in contrast to pentacene which exhibits no long‐range order in pure films. A model of the epitaxial relationship on Cu(100) is given, which suggests C? F???H bonding as a possible driving force for the bimolecular self‐assembly in addition to the still strong interaction between the substrate and the organic bilayer.     

Reactions of Nitro and Halonitro Derivatives of Aluminum(III) and Copper(II) Phthalocyanines with Concentrated Sulfuric Acid

Transformations of the complexes CuPc(4-NO₂)₄, CuPc(4-Br)₄(5-NO₂)₄, (OH)AlRs(4-NO₂)₄, and (OH)AlPc(4-Cl)₄(5-NO₂)₄ in concentrated sulfuric acid were studied by spectrophotometry. One protonated form of CuPc(4-Br)₄(5-NO₂)₄ and (OH)AlPc(4-NO₂)₄ and two protonated forms of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were detected experimentally and also by ZINDO1 calculations. Step protonation constants of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were determined by quantum-chemical calculations and acid-base titration; these complexes can be regarded as weak bases with respect to H₂SO₄. The kinetics of dissociation of the complexes at the MÄN bonds were studied. The rate of dissociation of the Cu(II) complexes and (OH)AlPc(4-NO₂)₄ is proportional to [MPc(R) _n ] and [H₃O⁺]². The rate of dissociation of (OH)AlPc(4-Cl)₄(5-NO₂)₄ showed a weak extremal dependence on the composition of the medium, which was explained by change of its structure in 17.0 M H₂SO₄. The electronic effect of substituents on the reaction center was considered with account taken of a complex mechanism of activation and fine details of the molecular structure of macrocyclic complexes.