Bond Length Determination Using XANES

Bianconi, A.; Dell’Ariccia, M.; Gargano, A.; Natoli, C. R.

doi:10.1007/978-3-642-50098-5_8

Cited by 63 publications

(42 citation statements)

References 3 publications

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“…The solution to this inconsistency was obtained by applying Natoli's rule (22) to these three reference complexes, which says that given comparable systems, the rising-edge energy position is related to the average bond distance by Hmet, hydroxymet. † Measured at the first inflection-point energy.…”

Section: +mentioning

confidence: 99%

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin

Wilson

Green

Mathews

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Hemoglobin (Hb) is the heme-containing O 2 transport protein essential for life in all vertebrates. The resting high-spin (S = 2) ferrous form, deoxy-Hb, combines with triplet O 2 , forming diamagnetic (S = 0) oxy-Hb. Understanding this electronic structure is the key first step in understanding transition metal-O 2 interaction. However, despite intense spectroscopic and theoretical studies, the electronic structure description of oxy-Hb remains elusive, with at least three different descriptions proposed by Pauling, Weiss, and McClureGoddard, based on theory, spectroscopy, and crystallography. Here, a combination of X-ray absorption spectroscopy and extended X-ray absorption fine structure, supported by density functional theory calculations, help resolve this debate. X-ray absorption spectroscopy data on solution and crystalline oxy-Hb indicate both geometric and electronic structure differences suggesting that two of the previous descriptions are correct for the Fe-O 2 center in oxy-Hb. These results support the multiconfigurational nature of the ground state developed by theoretical results. Additionally, it is shown here that small differences in hydrogen bonding and solvation effects can tune the ground state, tipping it into one of the two probable configurations. These data underscore the importance of solution spectroscopy and show that the electronic structure in the crystalline form may not always reflect the true ground-state description in solution.H emoglobin (Hb) is the iron-containing heme protein essential for oxygen transport in all vertebrates. The protein is an assembly of four globular subunits, each containing a heme B (protoporphyrin IX group) (1). The first characterization of Hb was done in the mid-1800s (2, 3), with the magnetic properties first elucidated in early 1900s. Later, Pauling and Coryell (4) showed that whereas resting venous Hb is paramagnetic, the oxygenated arterial form (oxy-Hb) is diamagnetic in nature. The first structure determination (X-ray diffraction) was done by Perutz et al. (5) in 1960, who was awarded the Nobel prize for this work. In 1974, the geometry of O 2 binding was shown to be end-on η 1 -Fe-O 2 , based on X-ray diffraction data on a biomimetic model complex (6), which was later confirmed by diffraction data on oxyHb. However, the debate over the electronic structure of O 2 binding in Hb and the nature of the Fe-O 2 bond continues today.Although the diamagnetic nature of oxy-Hb has been described by several different models, three have persisted. Starting from deoxy-Hb (Fe 2+ , S = 5/2) and O 2 (neutral, S = 1) and using a valence bond theory, Pauling proposed that the oxy-Hb is a Fe 2+ , S = 0 system that accepts one lone pair from the sp 2 hybridized O 2 , forming a dative bond (Scheme 1) (7). The Weiss model involves one-electron reduction of O 2 by the ferrous heme in deoxy-Hb (8), which leads to antiferromagnetic coupling between the Fe 3+ (S = 1/2) and O In this study, quantitative Fe K-edge XAS and density functional theory (DFT) calculations have ...

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Section: +mentioning

confidence: 99%

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin

Wilson

Green

Mathews

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…As it was shown in Refs. [4][5][6] the widely used Z þ 1 approximation [22] for including core hole screening has to be slightly modified for calculating the PEFS peaks caused by the second and third mechanisms mentioned in the Introduction. The matter is that the energies of the TM 3d shell originated MOs highly localized inside the TM atomic spheres are very sensitive to the inner potential variations.…”

Section: Incomplete Screening Model For Calculations Of Pefs In Tm K mentioning

confidence: 99%

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Vedrinskiǐ

Крайзман

Novakovich

et al. 2001

phys. stat. sol. (b)

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Polarized Ni K XANES of single crystal NiO is studied experimentally and theoretically for two crystal orientations relative to the polarization and wave vectors of incident X-ray beam. The spectra calculated by the full multiple scattering method for a spin-dependent cluster potential and incomplete screening of the core hole appear to be in an excellent agreement with the experiment. The low energy pre-edge peak is shown to be caused by the quadrupole transitions of the Ni 1s electron to an exciton-type state shifted down by $4 eV from the empty e g high-energy conduction band under the influence of the core hole potential. The feature caused by the Ni 1s ! e g band dipole transitions is also recognized in the spectrum. It is shown that the same mechanisms, which are responsible for the formation of the pre-edge fine structure in the oxides of early 3d-metals in 3d 0 state, work in the considered case as well. A comparative analysis outlining the significance of different mechanisms for the pre-edge structure formation in cases of early and late 3d-metal spectra is presented. The antiferromagnetic order of the absorber is taken into account within oneelectron approximation.Die polarisierte Ni K XANES von einkristallinem NiO wurde experimentell und theoretisch fü r zwei Kristallorientierungen relativ zum Polarisations-und Wellenvektor des einfallenden Rö ntgenstrahls untersucht. Die Spektren wurden nach der Full-multiple-scattering Methode fü r ein spinabhä ngiges Clusterpotential und fü r unvollstä ndige Abschirmung des Rumpfloches in exzellenter Ûbereinstimmung mit dem Experiment berechnet. Die niederenergetische Vorkantenabsorption wird durch Quadrupolü bergä nge von Ni 1s Elektronen in einen exzitonä hnlichen Zustand erklä rt, der durch das Rumpflochpotential um $4 eV gegenü ber dem unbesetzten e gartigen Leitungsband abgesenkt ist. Die aus den Ni 1s ! e g Dipolü bergä ngen berechneten Strukturen sind auch in den experimentellen Spektren zu erkennen. Es wird gezeigt, da im vorliegenden Fall die gleichen Mechanismen wirken, die auch fü r das Auftreten der Vorkantenabsorption bei den frü hen 3d-Metalloxiden im 3d 0 -Zustand verantwortlich sind. Eine vergleichende Analyse der Bedeutung der verschiedenen Mechanismen fü r das Entstehen der Vorkantenstruktur bei den Verbindungen der 3d-Metalle niedriger und hö herer Ordnungszahl wird durchgefü hrt.

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“…Sato et al 1 discovered the phase transition in CoFe cyanides by optical stimuli; Na 0.4 Co 1.3 Fe(CN) 6 and K 0.4 Co 1.3 Fe(CN) 6 show weak paramagnetism at low temperature ͑LT͒, and they become ferrimagnets upon visible-light ͑500-750 nm͒ irradiation. The ferrimagnetic behavior is preserved up to ϳ100 K. Moreover, irradiation of near-infrared light ͑1319 nm͒ transforms the ferrimagnetic phase to the LT phase with weak paramagnetism.…”

Section: Introductionmentioning

confidence: 99%

Local structure and electronic state of a photomagnetic material of CoW cyanide studied by x-ray-absorption fine structure spectroscopy

et al. 2002

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Bond Length Determination Using XANES

Cited by 63 publications

References 3 publications

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Local structure and electronic state of a photomagnetic material of CoW cyanide studied by x-ray-absorption fine structure spectroscopy

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