Understanding the reactivity of transition metal complexes involving multiple spin states

Harvey, Jeremy N.

doi:10.1016/s0010-8545(02)00283-7

Cited by 323 publications

(229 citation statements)

References 78 publications

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“…These research efforts provide valuable insight with respect to basic research about the interplay between theory and experiment. In this context, the development of new mechanistic paradigms, such as two-state reactivity (TSR), is a particular highlight, and TSR scenarios are meanwhile considered relevant in several areas of chemical and biological sciences far beyond the field of gas-phase ion chemistry (50,86). Inclusion of ligated systems does not only extend beyond the world of idealized ''naked'' atom chemistry (87), they also serve as more realistic models for active metal species capable of activating methane in the condensed phase.…”

Section: Discussionmentioning

confidence: 99%

Gas-phase activation of methane by ligated transition-metal cations

Schröder

Schwarz²

2008

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

237

135

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Motivated by the search for ways of a more efficient usage of the large, unexploited resources of methane, recent progress in the gas-phase activation of methane by ligated transition-metal ions is discussed. Mass spectrometric experiments demonstrate that the ligands can crucially influence both reactivity and selectivity of transition-metal cations in bond-activation processes, and the most reactive species derive from combinations of transition metals with the electronegative elements fluorine, oxygen, and chlorine. Furthermore, the collected knowledge about intramolecular kinetic isotope effects associated with the activation of C-H(D) bonds of methane can be used to distinguish the nature of the bond activation as a mere hydrogen-abstraction, a metal-assisted mechanism or more complex reactions such as formation of insertion intermediates or -bond metathesis.bond activation ͉ kinetic isotope effects ͉ mass spectrometry

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Section: Discussionmentioning

confidence: 99%

Gas-phase activation of methane by ligated transition-metal cations

Schröder

Schwarz²

2008

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

237

135

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“…High-spin and low-spin electron configurations of d 4 -d 7 transition ions in an octahedral ligand field, with their weak-field term symbols and spin quantum numbers [2].…”

Section: Methodsmentioning

confidence: 99%

“…The difference probably arises from strong N-H···OH2 hydrogen bonding undertaken by [Fe(3-bpp)2] 2+ in aqueous solution, which makes the 3-bpp ligands more electron rich by increasing the N δ− -H δ+ bond polarity (see below). More subtly, the involvement of high-spin intermediates in substitution reactions of low-spin complexes can lead to a change in mechanism and increase in reaction rate [3,7].…”

Section: Methodsmentioning

confidence: 99%

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

2016

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Abstract:The relationship between chemical structure and spin state in a transition metal complex has an important bearing on mechanistic bioinorganic chemistry, catalysis by base metals, and the design of spin crossover materials. The latter provide an ideal testbed for this question, since small changes in spin state energetics can be easily detected from shifts in the spin crossover equilibrium temperature. Published structure-function relationships relating ligand design and spin state from the spin crossover literature give varied results. A sterically crowded ligand sphere favors the expanded metal-ligand bonds associated with the high-spin state. However, steric clashes at the molecular periphery can stabilize either the high-spin or the low-spin state in a predictable way, depending on their effect on ligand conformation. In the absence of steric influences, the picture is less clear since electron-withdrawing ligand substituents are reported to favor the low-spin or the high-spin state in different series of compounds. A recent study has shed light on this conundrum, showing that the electronic influence of a substituent on a coordinated metal ion depends on its position on the ligand framework. Finally, hydrogen bonding to complexes containing peripheral N-H groups consistently stabilizes the low-spin state, where this has been quantified.

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“…These errors were comparable to typical structural rearrangements in the OEC metal cluster, induced by oxidation of the constituent ions (i.e., changes of Mn ligand bond-lengths in the 0.1-0.2 Å), and therefore required further analysis. In addition, hybrid functionals were known to overestimate the relative stability of high-spin over low-spin states of transition metal complexes (Koch & Holthausen 2001;Reiher et al 2001a), a difficulty that could be critical in the process of identifying the nature of ground electronic states, or in studies of spincrossover phenomena in transition metal complexes (Harvey 2001;Harvey et al 2003;Holthausen 2005;Reiher et al 2001a;Schroder et al 2000;Shaik et al 2002).…”

Section: Dft Studiesmentioning

confidence: 99%

Computational insights into the O2-evolving complex of photosystem II

et al. 2008

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Mechanistic investigations of the water-splitting reaction of the oxygen-evolving complex (OEC) of photosystem II (PSII) are fundamentally informed by structural studies. Many physical techniques have provided important insights into the OEC structure and function, including X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy as well as mass spectrometry (MS), electron paramagnetic resonance (EPR) spectroscopy and Fourier transform infrared spectroscopy applied in conjunction with mutagenesis studies. However, experimental studies have yet to yield consensus as to the exact configuration of the catalytic metal cluster and its ligation scheme. Computational modeling studies, including density functional (DFT) theory combined with quantum mechanics/molecular mechanics (QM/MM) hybrid methods for explicitly including the influence of the surrounding protein, have proposed chemically satisfactory models of the fully ligated OEC within PSII that are maximally consistent with experimental results. The inorganic core of these models is similar to the crystallographic model upon which they were based but comprises important modifications due to structural refinement, hydration and proteinaceous ligation which improve agreement with a wide range of experimental data. The computational models are useful for rationalizing spectroscopic and crystallographic results and for building a complete structure-based mechanism of water-splitting in PSII as described by the intermediate oxidation states of the OEC. This review summarizes these recent advances in QM/MM modeling of PSII within the context of recent experimental studies.

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Understanding the reactivity of transition metal complexes involving multiple spin states

Cited by 323 publications

References 78 publications

Gas-phase activation of methane by ligated transition-metal cations

Gas-phase activation of methane by ligated transition-metal cations

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

Computational insights into the O2-evolving complex of photosystem II

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