Prediction of high-valent iron K-edge absorption spectra by time-dependent Density Functional Theory

Chandrasekaran, P.; Stieber, S. Chantal E.; Collins, Terrence J.; Que, Lawrence; Neese, Frank; DeBeer, Serena

doi:10.1039/c1dt11331c

Cited by 95 publications

(164 citation statements)

References 53 publications

(87 reference statements)

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“…In order to elucidate the structure of the Co(II) species, three possible geometries of the transient Co(II) complex were tested by using DFT calculations. A Co(II) octahedral, square pyramidal and square planar geometries were considered depending on the numbers of water molecules coordinated to the cobalt For the calculations presented in figure 3, both the spin polarization contribution shown in Debeer et al 49 and the quadrupole transition operator are taken into consideration. .As shown in Fig.…”

Section: -Introductionmentioning

confidence: 99%

Tracking the Structural and Electronic Configurations of a Cobalt Proton Reduction Catalyst in Water

Moonshiram¹,

Gimbert‐Suriñach

Guda

et al. 2016

J. Am. Chem. Soc.

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Time resolved X-ray absorption spectroscopy (X-TAS) has been used to study the light induced hydrogen evolution reaction catalyzed by a highly stable tetradentate macrocyclic cobalt complex with the formula [LCo III Cl 2 ] + (L = macrocyclic ligand), [Ru(bpy) 3 ] 2+ photosensitizer and an equimolar mixture of sodium ascorbate/ascorbic acid electron donor in pure water. XANES and EXAFS analysis of a binary mixture of the octahedral Co(III) pre-catalyst and [Ru(bpy) 3 ] 2+ after illumination, revealed in-situ formation of a Co(II) intermediate with significantly distorted geometry and electron transfer kinetics of 51 ns. On the other hand, X-TAS experiments of the complete photocatalytic system in the presence of the electron donor showed the formation of a square planar Co(I) intermediate species within a few nanoseconds followed by its decay in the microsecond timescales. The Co(I) structural assignment is supported by calculations based on density functional theory (DFT). At longer reaction times, we observe the formation of the initial Co(III) species concomitant to the decay of Co(I), thus closing the catalytic cycle. The experimental Xray absorption spectra of the molecular species formed along the catalytic cycle are modeled using a combination of molecular orbital DFT calculations (DFT-MO) and Finite Difference Method (FDM). These findings allowed us to unequivocally assign the full mechanistic pathway followed by the catalyst as well as to determine the rate limiting step of the process, which consists in the protonation of the Co(I). This study provides a complete kinetics scheme for the hydrogen evolution reaction by a cobalt catalyst, revealing unique information for the development of better catalysts for the reductive side of hydrogen fuel cells.

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Section: -Introductionmentioning

confidence: 99%

Tracking the Structural and Electronic Configurations of a Cobalt Proton Reduction Catalyst in Water

Moonshiram¹,

Gimbert‐Suriñach

Guda

et al. 2016

J. Am. Chem. Soc.

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“…[35] Promising advances in TDDFT or DFT/CI-based (CI, configuration interaction) approaches have been made towards the calculation of various X-ray absorption and emission features relevant for iron complexes, [36,37,38,39] again with the potential of structural assigment or electronic structure calibration. [40,41] Nuclear resonance vibrational spectroscopy (NRVS), selectively probing the iron-containing vibrational modes using nuclear excitations with synchrotron radiation, has lately become an important tool in the bioinorganic chemistry of iron systems.…”

Section: Density Functional Theory Calculations Of Spectroscopic Propmentioning

confidence: 99%

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

et al. 2016

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In this minireview, we provide an account of the current state-of-the-art developments in the area of mono-and binuclear non-heme enzymes (NHFe and NHFe2) and the smaller NHFe(2) synthetic models, mostly from a theoretical and computational perspective. The sheer complexity, and at the same time the beauty, of the NHFe(2) world represent a challenge for both experimental as well as theoretical methods. We emphasize that the concerted progress on both theoretical and experimental side is a conditio sine qua non for future understanding, exploration and utilization of the NHFe(2) systems.After briefly discussing the current challenges and advances in the computational methodology, we review the recent spectroscopic and computational studies of NHFe(2) enzymatic and inorganic systems and highlight the correlations between various experimental data (spectroscopic, kinetic, thermodynamic, electrochemical) and computations. Throughout, we attempt to keep in mind the most fascinating and attractive phenomenon in the NHFe(2) chemistry which is the fact that despite the strong oxidative power of many reactive intermediates, the NHFe(2) enzymes perform catalysis with high selectivity. We conclude with our personal viewpoint and hope that further developments in quantum chemistry and especially in the field of multireference wave function methods are needed to have a solid theoretical basis for the NHFe(2) studies, mostly by providing benchmarking and calibration of the computationally efficient and easy-to-use DFT methods.

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“…[3,7,10,11]) and to investigate biological or biomimetic systems containing transition metal centers (see, e.g., Refs. [12][13][14][15][16][17][18]). Usually, XAS and XES are used as fingerprint techniques in such studies to identify the oxidation state, spin state, and local coordination environment of a metal center.…”

Section: Introductionmentioning

confidence: 99%

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

Bernadotte

Atkins

Jacob

2012

The Journal of Chemical Physics

147

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For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these socalled quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an originindependent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole andelectric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within timedependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes.2

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Prediction of high-valent iron K-edge absorption spectra by time-dependent Density Functional Theory

Cited by 95 publications

References 53 publications

Tracking the Structural and Electronic Configurations of a Cobalt Proton Reduction Catalyst in Water

Tracking the Structural and Electronic Configurations of a Cobalt Proton Reduction Catalyst in Water

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

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