Electronic properties of tetrakis(pentafluorophenyl)porphyrin (original) (raw)
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Physical Chemistry Chemical Physics, 2010
Porphyrins and their metal complexes are particularly well suitable for applications in photoelectronics, sensing, energy production, because of their chemical, electronic and optical properties. The understanding of the electronic properties of the pristine molecule is of great relevance for the study and application of the wide class of these compounds. This is notably important for the recently achieved in-vacuo synthesis of organo-metallic thin films directly from the pure free base organic-inorganic precursors in the vapor phase, and its interpretation by means of surface electron spectroscopies. We report on a combined experimental and theoretical study of the physical/chemical properties of tetraphenylporphyrin, H 2 TPP, deposited on the SiO 2 /Si(100) native oxide surface by supersonic molecular beam deposition (SuMBD). Valence states and 1s core level emissions of carbon and nitrogen have been investigated with surface photoelectron spectroscopies by using synchrotron radiation light. The interpretation of the spectra has been guided by density functional numerical experiments on the gas-phase molecule. Non-relativistic calculations were carried out for the valence states, whereas a two component relativistic approach in the zeroth-order regular approximation was used to investigate the core levels. The good agreement between theoretical and experimental analysis results in a comprehensive overview of the chemical properties of the H 2 TPP molecule, highly improving reliability in the interpretation of experimental photoemission spectra.
The present paper deals with the estimation of conformational stability and determination of electronic structures of H2-porphyrin-fulleropyrrolidine (1) and zincporphyrin–fulleropyrrolidine (2) dyads by ab initio (HF)and density functional theory (DFT) calculations in vacuo. In dyads 1 and 2, fulleropyrrolidine is directly linked to the tetrapyrrolic rings by ethylene subunits. Both HF and DFT calculations establish that possibility of photoinduced electron transfer (PET) phenomenon is higher in case of 2 compared to 1. Investigation on frontier molecular orbitals at different electronic states reveal that the highest occupied molecular orbital and the lowest unoccupied molecular orbital of these supramolecules is delocalized due to PET phenomenon. Generation of molecular electrostatic potential (MEP) maps by both HF and DFT calculations substantiate the PET phenomenon (as stated above) and establish that the direction of electron transfer occurs from the porphyrin subunits to the ...
A density functional study of the ground state electronic structure of phosphorus–porphyrins
Chemical Physics Letters, 2003
Geometries of the ground state and energies of the lower-lying excited singlet states of phosphorus-containing porphyrins were computed using DFT and TD-DFT methods, respectively, and compared with those of N-porphyrins. The P-analogues of porphyrins were obtained by successively replacing a NH-by a PH-unit or a N-by a P-atom within N-porphyrins. The goal of this theoretical study is to elucidate the modifications in the electronic structure and to predict the shift of Q-and B-bands in the UV-VIS absorption spectrum of porphyrins following substitution of nitrogen by phosphorus atoms. The interesting features could be of help in the identification of the P-substituted porphyrins that are not known yet.
Ring-expanded porphyrins as an approach towards highly conductive molecular semiconductors
Chemical Physics Letters, 1993
As an approach to obtainiq molecular semiconductors with high conductivity, it was attempted to lower the activation energy of conduction by enlargiqthe n-conjugated system in porphyrin materials. An anthraporphyrin (ZnTAnP) has been synthesized for the fast time, and the spectroscopic, electrochemical and semiconductive properties have been characterized as a function of increasing molecular size, in the order: tetraphenylporphyrin (ZnTPP), tetrabenzoporphyrin (ZnTBP), tetranaphthaloporphyrin (ZnTNP), and ZnTAnP. With enlargement of the macrocycle, the Q band shifts to the red, and the absolute values of oxidation and reduction potentials become smaller. Room temperature conductivities of air-doped ZnTPP, ZnTBP, ZSNP, and ZnTAnP thin films are < lo-", 4~ lo-lo, 3~ lo-' and 1 x lo-' W' cm-', respectively. The smaller conductivity of ZnTAnP appears due to the formation of a stable charge transfer complex with oxygen.
International Journal of Quantum Chemistry, 2011
DFT and TDDFT calculations at the level of PBE0/6-31G(d)/6-31þG (d) were performed systematically on seven porphyrins with symmetrical mesosubstitutents. Our results show that the planarity of the free base porphyrin (BP) are affected by the introduction of substitutents at the meso-position of the ring. Geometrical studies show that the introduction of electron-withdrawing groups brings about in-plane deformation in the porphyrin ring, whereas the bulky substitutents make an out-of-plane deformation. However, FMO's diagram shows that electronwithdrawing groups alter the degeneracy of the HOMO and HOMO À1 orbtial. Up on introduction of substituents at the meso-position, the Q band FMOs transitions were the same as in the case of free BP; however, the oscillator strength is changed. Electron releasing substituted at the meso-position shows bathochromic shift in the Q band region. However, the intensity or the hyperchromic shift is higher for the electron withdrawing groups. Solvation studies show that Q bands are blue shifted and B bands are red shifted, whereas the intensity of the B bands was highly enhanced compared with the Q bands. These theoretical studies would be helpful in designing new porphyrins for the photodynamic therapy and dye-sensitized solar cell applications.
Journal of Molecular Modeling, 2019
Electronic and spectroscopic properties of tetracationic 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphyrin (TMPyP) were investigated in the framework of the density functional theory (DFT). Modeling of implicit solvent, charge effects, and medium acidity were performed and compared with experimental results. Various hybrid exchange correlation functionals in the Kohn-Sham Scheme of the DFT were employed and various porphyrin models were constructed, simulating different environmental conditions. Since porphyrins present several technological applications with a plethora of interacting systems and the optical spectra profiles are often used to characterize these macrocyclic compounds, the study performed here aims to stablish a correct description of the UV-Vis spectrum. These results allowed to reproduce, both qualitatively as well as quantitatively, the Soret band of the TMPyP.
Nano Research, 2014
We report on large work function shifts induced by the coverage of several organic semiconducting (OSC) films commonly used in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) with a porphyrin aggregated layer. The insertion between the organic film and the aluminum cathode of an aggregated layer based on the meso-tetrakis(1-methylpyridinium-4-yl) porphyrin chloride (porphyrin 1), with its molecules adopting a face-to-face orientation parallel to the organic substrate, results in a significant shift of the OSC work function towards lower values due to the formation of a large interfacial dipole and induces large enhancement of either the OLED or OPV device efficiency. OLEDs based on poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-2,1',3-thiadiazole)] (F8BT) and incorporating the porphyrin 1 at the cathode interface exhibited current efficiency values up to 13.8 cd/A, an almost three-fold improvement over the efficiency of 4.5 cd/A of the reference device. Accordingly, OPVs based on poly(3hexylthiophene) (P3HT), [6,6]-phenyl-C 61 butyric acid methyl ester (PC 61 BM) and porphyrin 1 increased their external quantum efficiencies to 4.4% relative to 2.7% for the reference device without the porphyrin layer. The incorporation of a layer based on the zinc meso-tetrakis (1-methylpyridinium-4-yl)porphyrin chloride (porphyrin 2), with its molecules adopting an edge-to-edge orientation, also introduced improvements, albeit more modest in all cases, highlighting the impact of molecular orientation.
Journal of The American Chemical Society, 2006
Oxidation of a directly meso-meso linked cyclic porphyrin tetramer 2 gave a porphyrin sheet 3. The symmetric square structure of 3 is indicated by its simple 1 H NMR spectrum that exhibits only two signals for the porphyrin -protons. The absorption spectrum of 3 displays characteristic Soret-like broad bands and weak Q-bands, and its magnetic circular dichroism (MCD) spectrum exhibits a negative Faraday A term at the 762 nm band as a rare case, indicating the absorption as a transition from a nondegenerate level to a degenerate level. A slightly longer S1-state (1.1 ps) and smaller TPA cross section (2750 GM) than a tetrameric linear porphyrin tape also indicate its unique electronic properties. The porphyrin sheet 3 forms stable 1:2 complexes with guest molecules G1 and G2, whose 1 H NMR spectra exhibit remarkable downfield shifts for the guest protons that are located just above the cyclooctatetraene (COT) core of 3, whereas the imidazolyl protons bound to the zinc(II) porphyrin local cores are observed at slightly upfield positions. These results have been qualitatively accounted for in terms of the presence of a strong paratropic ring current around the COT core that propagates through the whole π-electronic network of 3, hence competing with and canceling the weak diatropic ring currents of the local zinc(II) porphyrins. This explanation was supported by DFT calculation performed at the GIAO-B3LYP/6-31G* level, which indicated large positive NICS values within the COT core and small NICS values within the local zinc(II) porphyrins.