Electron Autodetachment from Isolated Nickel and Copper Phthalocyanine−Tetrasulfonate Tetraanions: Isomer Specific Rates (original) (raw)
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Electron affinity states of metal supported phthalocyanines measured by tunneling spectroscopy
Journal of Porphyrins and Phthalocyanines, 2012
Orbital Mediated Tunneling Spectroscopy OMTS (elastic electron tunneling) was employed in measuring electron affinity levels (EA) of unsubstituted, alkylated, sulfonated, and metalated phthalocyanines (Pc) adsorbed as single molecules or aggregates on metal substrates and imbedded in metal-insulator-metal (M-I-M) devices. MPc complexes were vapor deposited, solution phase doped, or transferred as Langmuir-Blodgett films. It was determined that while the nature of the substituents has a large effect on the gas phase electron affinities, they play a minimal role on the electron affinities of metal supported phthalocyanines. Moreover, the orientation of monolayer films and the method of film deposition (vapor, solution, Langmuir-Blodgett) also appear to play only a minor role in determining the electron affinities. Electrochemical reduction potentials obtained for the solution phase molecular systems are compared to the OMTS data and a strong correlation is observed. In contrast, the predicted EA values for the gas phase molecules show little correspondence with their OMTS equivalents for adsorbed phthalocyanines. Inelastic scattering from phthalocyanine p�p* transitions and metal centered d-d transitions are observed for chromophores imbedded in tunnel diodes. Both the observed lowest spin forbidden transitions and the calculated gas phase HOMO-LUMO gaps are only weakly affected by Pc substitution and surface orientation.
Organic Electronics, 2007
Nickel phthalocyanine (NiPc) thin films were grown stepwise on polycrystalline gold and silver substrates and the formed interfaces were characterized by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS). The variation of the XPS core level binding energy with NiPc film thickness yields information about band bending and interface dipoles. The valence band structure of the NiPc thin films was determined by UPS and exhibits four main features at binding energies 1.50 eV, 3.80 eV, 6.60 eV and 8.85 eV, respectively. The NiPc highest occupied molecular orbital (HOMO) cut-off was measured at 1.00eVfromtheanalyzerFermilevelandfromthemeasuredworkfunctionchangeofthegrowingNiPcfilmafinalworkfunctionvalueforNiPcwasestimatedat3.90±0.10eV.ThemainC1speakoftheNiPcfilm(1.00 eV from the analyzer Fermi level and from the measured work function change of the growing NiPc film a final work function value for NiPc was estimated at 3.90 ± 0.10 eV. The main C1s peak of the NiPc film (1.00eVfromtheanalyzerFermilevelandfromthemeasuredworkfunctionchangeofthegrowingNiPcfilmafinalworkfunctionvalueforNiPcwasestimatedat3.90±0.10eV.ThemainC1speakoftheNiPcfilm(5.0 nm) consists of two components at 284.8 eV (C-C bonds), 286.2 eV (C-N bonds) reflecting photoemission from multiple carbon sites within the molecule and a satellite at 287.9 eV, whereas the Ni2p and N1s peaks appear at 855.9eVand855.9 eV and 855.9eVand399.3 eV, respectively and are due to Ni-N bonds. The energy level diagrams of the NiPc/Au and NiPc/Ag interfaces were determined from a combination of the XPS and UPS results, yielding a hole injection barrier of 0.90 ± 0.10 eV for both substrates.
The journal of physical chemistry. A, 2007
As an indication of damage induced by hot electrons in an organic electronic material, the desorption of F- ions from a thin perfluorinated copper phthalocyanide film on SiO2 under low-energy (0-25 eV) electron impact has been recorded mass spectrometrically. Yields and damage cross sections are very low. No strong features due to negative ion resonances are found in the electron energy dependence of the desorption yield; rather the yield function rises from a threshold at about 5-6 eV continuously (with some weak structure) throughout the measured range. We discuss these findings in terms of the electronic structure of the film, as well as parameters influencing the relevant bond breaking process. We emphasize the strong influence of energy redistribution, which quenches normally long-lived negative ion resonances and selects localized and strongly repulsive excitations, as often observed in electronically induced bond breaking at surfaces. The improved understanding should be help...
The European Physical Journal B, 2009
The objective of this interdisciplinary paper was to study theoretically and experimentally the electronic part of charge carrier transport in the class of sodium salts of sulphonated Ni phthalocyanine as candidates for p-type channels in organic field-effect transistors. These materials were selected because of their enhanced solubility as compared to their non-sulphonated counterparts. The values of the field-effect charge carrier mobility determined on the OFET structures using NiPc(SO3Na)x films were much higher than the charge carrier mobility obtained on the respective device prepared from non-substituted phthalocyanine. In order to explain differences between charge carrier mobility of sulphonated and non-sulphonated Ni phthalocyanines, quantum chemistry studies of molecular aggregates were performed. Quantum chemistry modeling of the semiconductive molecular systems is new and progressive -we highlighted factors at the molecular level which led to the enhancement of the charge carrier mobility in systems containing SO3Na groups.
Journal of Physical Chemistry C, 2008
A first-principles study is performed to explore the electronic and magnetic properties of several 3d transition metal phthalocyanines (including MnPc, FePc, NiPc, and CuPc) adsorbed on a Au(111) surface. Our results show that the most favorite adsorption site is the top site for MnPc molecule whereas it is the hcp site for other molecules. The electronic structures of MnPc and FePc change obviously when they are adsorbed onto the Au(111) surface, while those of NiPc and CuPc change slightly near the Fermi level due to the weak molecule-surface interactions. By analyzing the properties of d orbitals at the spatial and energy scales, we have discussed the possible Kondo effect related to these metal phthalocyanines adsorbed on the Au
Photoemission from valence bands of transition metal-phthalocyanines
Journal of Electron Spectroscopy and Related Phenomena, 2011
Angular dependencies of ultraviolet photoelectron spectrum of transition metal-phthalocyanines (TM-Pcs), NiPc and CoPc, have been studied by using multiple-scattering theory to explore the electronic structure of the organometallic complexes influenced by central metal atom. The calculated angular distributions of photoelectrons for the highest occupied molecular orbital (HOMO: a 1u) from the two single systems are nearly the same and represent well the experimental results obtained for the wellordered monolayer on the highly oriented pyrolytic graphite substrate. The central metal atoms almost have no contribution on the HOMO distribution, which mainly comes from the carbon atoms of Pc ring. Moreover, the modification of the distribution for orbital upon adsorption as well as the scattering effects of the central metal on the photoemission intensities are negligible for the major.
Journal of Physics: Conference Series, 2005
Nickel Phthalocyanine (NiPc) thin films (~25m thick) were grown stepwise on a polycrystalline Au substrate and the interface was characterized by X-Ray and Ultraviolet Photoelectron Spectroscopies (XPS, UPS). The C1s peak of the bulk (~5 nm) NiPc film was resolved into three components reflecting photoemission from multiple sites within the molecule. The peak at 284.8 eV corresponds to C-C bonds, the one at 286.2 eV to C-N bonds, while the last one at 287.9 eV is satellite of the main peak. The Ni 2p and N1s peaks appear at ~855.9 eV and ~399.3 eV respectively and are due to Ni-N bonds. The NiPc Highest Occupied Molecular Orbital (HOMO) cut-off position was determined from the valence band spectrum of the bulk organic film, and was found at ~1.00 eV from the analyser Fermi level. The work function of the Au foil and the bulk NiPc film were found to be 5.20±0.05 eV and 4.20±0.05 eV respectively. The combination of UPS and XPS results led to the determination of the energy level diagram of the NiPc/Au interface.