Electronic excitations in vanadium oxide phthalocyanine studied via resonant soft X-ray emission and resonant inelastic X-ray scattering

Zhang, Yufeng; Wang, Shancai; Learmonth, Timothy; Pluciński, Ł.; Matsuura, A. Y.; Bernardis, Sarah; O’Donnell, Cian; Downes, James E.; Smith, Kevin

doi:10.1016/j.cplett.2005.07.066

Cited by 18 publications

(7 citation statements)

References 24 publications

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“…More recently, it has become possible to resolve considerable fine structure with state-of-the-art photon sources and monochromators, as demonstrated in individual case studies for phthalocyanines and porphyrins. 19,30,[33][34][35][36][37][38] The corresponding core level binding energies [36][37][38][39][40][41] have been determined in some cases by x-ray photoelectron spectroscopy, and the valence states by soft x-ray emission spectroscopy, 33-37 photoemission, 38,42,43 inverse photoemission, 44 and scanning tunneling spectroscopy. 45,46 Analogous NEXAFS studies exist for porphyrins.…”

Section: Transition Metal 2p Edgesmentioning

confidence: 99%

X-ray absorption spectroscopy of biomimetic dye molecules for solar cells

Cook

Liu

Yang

et al. 2009

The Journal of Chemical Physics

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Dye-sensitized solar cells are potentially inexpensive alternatives to traditional semiconductor solar cells. In order to optimize dyes for solar cells we systematically investigate the electronic structure of a variety of porphyrins and phthalocyanines. As a biological model system we use the heme group in cytochrome c which plays a role in biological charge transfer processes. X-ray absorption spectroscopy of the N 1s and C 1s edges reveals the unoccupied molecular orbitals and the orientation of the molecules in thin films. The transition metal 2p edges reflect the oxidation state of the central metal atom, its spin state, and the ligand field of the surrounding N atoms. The latter allows tuning of the energy position of the lowest unoccupied orbital by several tenths of an eV by tailoring the molecules and their deposition. Fe and Mn containing phthalocyanines oxidize easily from +2 to +3 in air and require vacuum deposition for obtaining a reproducible oxidation state. Chlorinated porphyrins, on the other hand, are reduced from +3 to +2 during vacuum deposition at elevated temperatures. These findings stress the importance of controlled thin film deposition for obtaining photovoltaic devices with an optimum match between the energy levels of the dye and those of the donor and acceptor electrodes, together with a molecular orientation for optimal overlap between the pi orbitals in the direction of the carrier transport.

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Section: Transition Metal 2p Edgesmentioning

confidence: 99%

X-ray absorption spectroscopy of biomimetic dye molecules for solar cells

Cook

Liu

Yang

et al. 2009

The Journal of Chemical Physics

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“…Herein, we demonstrate the ability of 2p3d RIXS to map the multiplet structure of ferrous and ferric iron chlorides. The present study marks one of the relatively few applications of 2p3d RIXS to chemical systems comprised of discrete molecular units. − The presented data are compared to existing optical data, and the advantages and limitations of 2p3d RIXS compared to conventional optical measurements are highlighted. The present study forms the foundation for future applications of 2p3d RIXS to iron-based catalysts.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Ligand Field Spectra of Ferrous and Ferric Iron Chlorides Using 2p3d RIXS

et al. 2017

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Ligand field spectra provide direct information about the electronic structure of transition metal complexes. However, these spectra are difficult to measure by conventional optical techniques due to small cross sections for d-to-d transitions and instrumental limitations below 4000 cm. 2p3d resonant inelastic X-ray scattering (RIXS) is a second order process that utilizes dipole allowed 2p to 3d transitions to access d-d excited states. The measurement of ligand field excitation spectra by RIXS is demonstrated for a series of tetrahedral and octahedral Fe(II) and Fe(III) chlorides, which are denoted Fe(III)-T, Fe(II)-T, Fe(III)-O, and Fe(II)-O. The strong 2p spin-orbit coupling allows the measurement of spin forbidden transitions in RIXS spectroscopy. The Fe(III) spectra are dominated by transitions from the sextet ground state to quartet excited states, and the Fe(II) spectra contain transitions to triplet states in addition to the spin allowed Γ →Γ transition. Each experimental spectrum is simulated using a ligand field multiplet model to extract the ligand field splitting parameter 10Dq and the Racah parameters B and C. The 10Dq values for Fe(III)-T, Fe(II)-T, and Fe(III)-O are found to be -0.7, -0.32, and 1.47 eV, respectively. In the case of Fe(II)-O, a single 10Dq parameter cannot be assigned because Fe(II)-O is a coordination polymer exhibiting axially compressed Fe(II)Cl units. TheT → E transition is split by the axial compression resulting in features at 0.51 and 0.88 eV. The present study forms the foundation for future applications of 2p3d RIXS to molecular iron sites in more complex systems, including iron-based catalysts and enzymes.

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“…We note that this technique has been previously used to obtain damage free RIXS spectra on a vanadyl phthalocyanine complex. 9 A second concern in soft X-ray emission measurements is that selfabsorption of emitted X-rays can distort spectra, giving inaccurate intensitites. 13 The self-absorption of X-ray radiation is sensitive to the attenuation length of ingoing and outgoing X-ray beams, and consequently, the amount of self-absorption can be modified by altering the sample geometry chosen in the experiment.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Herein, we demonstrate the ability of 2p3d resonant inelastic X-ray scattering (RIXS) to experimentally determine both the spin-allowed and the spin-forbidden transitions in a series of molecular vanadium complexes. While 2p3d RIXS has seen growing interest within the condensed matter physics and catalysis communities, − there have been comparatively few molecular applications of 2p3d RIXS spectroscopy within the chemistry community. − In this contribution, we present RIXS spectra for a vanadium series comprising V III (acac) 3 , V IV O(acac) 2 , and V IV O(TPP) (where acac = acetylacetonate and TPP = tetraphenylporphyrin). The RIXS spectra contain information about ligand field strength, oxidation state, and metal–ligand covalency, providing a means to experimentally determine the ligand field parameters.…”

Section: Introductionmentioning

confidence: 99%

Measuring Spin-Allowed and Spin-Forbidden d–d Excitations in Vanadium Complexes with 2p3d Resonant Inelastic X-ray Scattering

et al. 2016

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Spectroscopic probes of the electronic structure of transition metal-containing materials are invaluable to the design of new molecular catalysts and magnetic systems. Herein, we show that 2p3d resonant inelastic X-ray scattering (RIXS) can be used to observe both spin-allowed and (in the V case) spin-forbidden d-d excitation energies in molecular vanadium complexes. The spin-allowed d-d excitation energies determined by 2p3d RIXS are in good agreement with available optical data. In V(acac), a previously undetected spin-forbidden singlet state has been observed. The presence of this feature provides a ligand-field independent signature of V. It is also shown that d-d excitations may be obtained for porphyrin complexes. This is generally prohibitive using optical approaches due to intense porphyrin π-to-π* transitions. In addition, the intensities of charge-transfer features in 2p3d RIXS spectroscopy are shown to be a clear indication of metal-ligand covalency. The utility of 2p3d RIXS for future studies of complex inorganic systems is highlighted.

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Electronic excitations in vanadium oxide phthalocyanine studied via resonant soft X-ray emission and resonant inelastic X-ray scattering

Cited by 18 publications

References 24 publications

X-ray absorption spectroscopy of biomimetic dye molecules for solar cells

X-ray absorption spectroscopy of biomimetic dye molecules for solar cells

Measurement of the Ligand Field Spectra of Ferrous and Ferric Iron Chlorides Using 2p3d RIXS

Measuring Spin-Allowed and Spin-Forbidden d–d Excitations in Vanadium Complexes with 2p3d Resonant Inelastic X-ray Scattering

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