Density Functional Theory Applications to Transition Metal Problems

Koch, Wolfram; Hertwig, Roland H.

doi:10.1002/0470845015.cda014

Cited by 12 publications

(19 citation statements)

References 79 publications

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“…For the successive M-CO bond energies in Fe(CO)s + and Ni(CO)4, and the first M-CO bond energy in the Cr, Mo, W triad of M(CO)6, B3LYP gives very good agreement with experiment, with an average error of only 2.6 kcal/mol, and the results are in most cases within the experimental error bars. 47,48 For MnO3(O-H) -, which is the only system closely related to the complexes studied in the present paper where an accurate value of an O-H bond strength is available experimentally, 49 the B3LYP result was found to be in good agreement with experiment, with values of 76.0 and 79.2 kcal/mol, respectively. 50,51,52 It can furthermore be pointed out that nonhybrid DFT methods, which do not include Hartree-Fock exchange, are not yet of sufficient accuracy to study the type of problems studied here since they give errors in computed MnO-H bond strengths of about 20 kcal/mol.…”

Section: Computational Detailssupporting

confidence: 67%

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

2000

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Hybrid density functional theory is used to study reasonably realistic models of the oxygen-evolving manganese complex in photosystem II. Since there is not yet any X-ray structure of the complex, other types of experimental and theoretical information are used to construct the model complexes. In these complexes, three manganese centers are predicted to be closely coupled by mu-oxo bonds in a triangular orientation. Using these models, the previously suggested oxygen radical mechanism for O2 formation is reinvestigated. It is found that the oxygen radical in the S3 state now appears in a bridging position between two manganese atoms. It is still suggested that only one manganese atom is redox-active. Instead, a number of surprisingly large trans-effects are found, which motivate the existence and define the function of the other manganese atoms in the Mn4 cluster. Calcium has a strong chelating effect which helps in the creation of the necessary oxygen radical. In the present model the chemistry preceding the actual O-O bond formation occurs in an incomplete cube with a missing corner and with two manganese and one calcium in three of the corners. The external water providing the second oxygen of O2 enters in the missing corner of the cube. The present findings are in most cases in good agreement with experimental results as given in particular by EXAFS.

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Section: Computational Detailssupporting

confidence: 67%

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

2000

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“…13 In addition, many reviews have noted that DFT methods are not overly sensitive to the size and quality of basis sets. 10,11 After optimization at the level of UB3LYP/Stuttgart+6-311++G(d,p), we compute single-point energies for most triplet stationary points using two other DFT methods, UmPW1PW91 and UB1LYP. Single-point energies for RB3LYP optimized singlet stationary points were also obtained using RmPW1PW91.…”

Section: Methodsmentioning

confidence: 99%

“…This is consistent with the experience that structural parameters predicted by B3LYP, even with modest basis sets, are of very good accuracy and, unlike energies, geometries and vibrational frequencies tend to be insensitive to the choice of functional employed. 10,11 In a few cases on the triplet PES, a transition state found at the level of UB3LYP/Stuttgart+6-311++G(d,p) actually disappears using the other DFT methods and energies are calculated to lie below the reactant ground-state asymptote, resulting in reported "barrier Single-point energies for all structures optimized at the level of UB3LYP/Stuttgart 6-311++G(d,p). d Although the geometry and spin state of these species were not described in ref 13, the energies most likely refer to intermediates along the singlet spin surface (compare to 1 TSβH and 7 in Table 3; see text for details).…”

Section: Methodsmentioning

confidence: 99%

“…Nonetheless, it is well established that B3LYP captures the essential features of the potential energy surface (PES) that govern transition metal cation chemistry with much less effort than computationally demanding multireference configuration interaction approaches such as CCSD(T) theory. 10,11 By comparison, neutral transition metal atom chemistry has been less extensively explored, although the body of experimental and theoretical data is expanding, particularly for the early second-row transition metals Y, Zr, and Nb. 12,13 We have studied the chemical kinetics of Zr (4d 2 5s 2 , 3 F) with ethylene and propylene at 300 K using a fast flow reactor equipped with detection by photoionization mass spectrometry (PIMS) at 157 nm.…”

Section: Introductionmentioning

confidence: 99%

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Singlet and Triplet Reaction Paths for Gas-Phase Zr + C₂H₄ by Density Functional Theory

2001

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We use the B3LYP density functional theory with a large basis set to characterize stationary points on both triplet and singlet potential energy surfaces for the gas-phase reaction Zr + C 2 H 4 f ZrC 2 H 2 + H 2 . The previously described stepwise rearrangement path occurs on the triplet surface, requiring passage over a substantial exit channel barrier. A new, lower energy triplet path involves concerted rearrangement of the HZrC 2 H 3 insertion intermediate directly to a weakly bound, product-like complex with no exit channel barrier to triplet products. A new low-energy singlet path involves stepwise rearrangement from HZrC 2 H 3 to the strongly bound dihydrido species H 2 ZrC 2 H 2 , which then dissociates to singlet products over a small exit channel barrier of 4 kcal/mol. We argue that the singlet path is more consistent than either triplet path with the experimental product kinetic energy distribution, which peaks at 3-5 kcal/mol. This in turn suggests that access of the singlet surface via fast intersystem crossing from the triplet to singlet metallacyclopropane complex competes effectively, perhaps dominating at low collision energy. As in earlier work, B3LYP places key transition state energies too high by 6-9 kcal/mol. The mPW1PW91 density functional gives much more realistic energies.

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“…The calculated successive Ni -CO bond energies at the B3LYP level (Blomberg et al 1996) fall more or less within the experimental error bars. Finally, the first M-CO bond energy has been calculated for the M(CO) 6 complexes of the Cr, Mo, W triad using both the B3LYP (Koch & Hertwig, 1998) and the BP (Li et al 1994) functionals. The experimental uncertainty for these M -CO bond energies is only 2 kcal mol x1 (Lewis et al 1984), and for the Mo and W complexes the calculated M -CO bond energies fall within these error bars for both functionals used.…”

Section: Density Functional Theorymentioning

confidence: 99%

Mechanisms of metalloenzymes studied by quantum chemical methods

Siegbahn

2003

Quart. Rev. Biophys.

196

234

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The study of metalloenzymes using quantum chemical methods of high accuracy is a relatively new field. During the past five years a quite good understanding has been reached concerning the methods and models to be used for these systems. For systems containing transition metals hybrid density functional methods have proven both accurate and computationally efficient. A background on these methods and the accuracy achieved in benchmark tests are given first in this review. The rest of the review describes examples of studies on different metalloenzymes. Most of these examples describe mechanisms where dioxygen is either formed, as in photosystem II, or cleaved as in many other enzymes like cytochrome c oxidase, ribonucleotide reductase, methane mono-oxygenase and tyrosinase. In the descriptions below high emphasis is put on the actual determination of the transition states, which are the key points determining the mechanisms.

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Density Functional Theory Applications to Transition Metal Problems

Cited by 12 publications

References 79 publications

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

Singlet and Triplet Reaction Paths for Gas-Phase Zr + C₂H₄ by Density Functional Theory

Mechanisms of metalloenzymes studied by quantum chemical methods

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Density Functional Theory Applications to Transition Metal Problems

Cited by 12 publications

References 79 publications

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

Theoretical Models for the Oxygen Radical Mechanism of Water Oxidation and of the Water Oxidizing Complex of Photosystem II

Singlet and Triplet Reaction Paths for Gas-Phase Zr + C2H4 by Density Functional Theory

Mechanisms of metalloenzymes studied by quantum chemical methods

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Singlet and Triplet Reaction Paths for Gas-Phase Zr + C₂H₄ by Density Functional Theory