On the mechanisms of aromatic substitution reactions

Takabe, Teruhiro; Takenaka, Kiyoshi; Yamaguchi, Kizashi; Fueno, Takayuki

doi:10.1016/0009-2614(76)80410-1

Cited by 27 publications

(6 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Meyer and his collaborators36, 37 have extended PCET theory to multi‐sites (MS) electron‐proton transfer (EPT) theory that has been applied for water splitting reaction at OEC of PSII. Extension of broken‐symmetry (BS) MO methods50, 51 to PCET and MS EPT processes will be an interesting problem that is discussed elsewhere.…”

Section: Derivations Of Working Hypotheses For Theoretical Calculationmentioning

confidence: 99%

See 1 more Smart Citation

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Saitô

Yamanaka

Kanda

et al. 2011

Int J of Quantum Chemistry

View full text Add to dashboard Cite

Recently, Umena et al. have revealed the X-ray diffraction structure of the CaMn 4 O 5 cluster in the oxygen evolving complex (OEC) of photosystem II (PSII) refined to 1.9 Å resolution. Their X-ray structure has first elucidated hydrogen-bonding networks and proton release pathways at OEC of PSII. Here, several working hypotheses Additional Supporting Information may be found in the online version of this article Correspondence to: S. Yamanaka; e-mail: syama@chem.sci.osaka-u.ac.jp Contract grant sponsor: Grants-in-Aid for Scientific Research; Contract grant numbers: 19750046, 19350070, 18350008, 23550016 (heuristic principles) for water splitting reaction are derived from their X-ray structure for theoretical modeling. These hypotheses suggest how water can be oxidized at OEC of PSII: namely possible reaction mechanisms for the reaction. To confirm them, we have also performed broken-symmetry (BS) UB3LYP calculations for active site models based on their XRD structure. The bond lengths of formal Mn(V)AO with labile dp-pp bonds are optimized to clarify possible roles of the species that are often introduced as a key intermediate in the catalytic (Kok) cycle for water splitting reaction at OEC of PSII. Location of the transition structure for the oxygen-oxygen (OAO) bond formation is also performed by the energy optimization technique. The natural orbital (NO) analysis of the UB3LYP solutions has been performed to obtain the natural molecular orbitals and their occupation numbers that have been useful for classification of localized d-electrons, labile chemical bonds and closed-shell (valence) orbitals. The localized d-electrons characterized by the NO analysis are the origins for the magnetism revealed by ENDOR and other magnetic experiments. On the other hand, the nature of labile (soft) dp-pp bonds responsible for the OAO bond formation has been investigated on the basis of chemical indices such as effective bond order (b), diradical character (y), and spin density (Q) indices that are calculated using the orbital overlap between broken-symmetry orbitals. These chemical indices have been calculated for the transition structure of the OAO bond formation at OEC of PSII. Implications of present computational results are discussed in relation to the derived hypotheses and available accumulated experimental results.

show abstract

Section: Derivations Of Working Hypotheses For Theoretical Calculationmentioning

confidence: 99%

“…(5f). The electron‐pair transfer (5g)50, 51 is conceivable for highly electrophilic oxygen site, where Mn(X‐2) is assumed to be high‐spin. …”

Section: Hybrid Dft Calculations For Active Intermediates and Tranmentioning

confidence: 99%

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Saitô

Yamanaka

Kanda

et al. 2011

Int J of Quantum Chemistry

View full text Add to dashboard Cite

show abstract

“…Therefore the electronic structure of this valence‐fluctuated system is more or less a mixing state of 1c and 1e (= 1cc ). The low‐spin BS solution for the complex after singlet spin projection (see Supporting Information) is indeed given by the mixing of both structures 1c (G) and 1e (= 1cc ) (electron transfer (ET)(S))77–79 where N is the normalizing factor, and θ 1 and θ 2 denote the HOMO(D) and LUMO(A) mixing parameters for BS orbitals obtained by DFT calculations. …”

Section: Theoretical Backgroundsmentioning

confidence: 99%

Effect of the medium on the stereostructure of poly(methyl methacrylate) synthesized in ionic liquids

Zhang

Wang

et al. 2006

J of Applied Polymer Sci

View full text Add to dashboard Cite

Poly(methyl methacrylate) (PMMA) was synthesized in different ionic liquids (IL) by free radical polymerization. The average molecular weight and polydispersity of the PMMA were measured by gel permeation chromatography. It is found that ILs have effect not only on the molecular weights but also on the stereostructure of PMMA. From the FTIR and NMR analysis, it was confirmed that the chemical structure of PMMA synthesized in ILs was similar to the one obtained in conventional solvents while the stereostructure was influenced by the different IL used.

show abstract

“…Therefore, a simple force‐field model does not work for molecular dynamics (MD) simulation of these reactions involving electron‐transfer processes. The quantum‐mechanical (QM) method by the use of the spin‐restricted Hartree–Fock (RHF) approach also breaks down because of its inapplicability to the processes, indicating the necessity of more flexible molecular orbital models 3, 4.…”

Section: Introductionmentioning

confidence: 99%

The electronic structure and magnetic property of metal‐oxo, porphyrin manganese‐oxo, and μ‐oxo‐bridged manganese porphyrin dimer

Koizumi

Shoji

Nishiyama

et al. 2004

Int J of Quantum Chemistry

View full text Add to dashboard Cite

ABSTRACT:Hybrid density functional theory (HDFT) and post Hartree-Fock CCSD(T) methods are applied to elucidate the binding energies and the optimized MOO distances of transition metal oxides: MO (M ϭ Cr, Mn, Fe, Co, Ni, Cu). The HDFT method can reproduce the CCSD(T) results, in agreement with the experimental ones. The nature of the manganese-oxygen bonds in the Mn(VI)OO, Mn(IV)OO porphyrin (PP), and Mn(V)OO PP systems are examined in relation to possible mechanisms of oxygen evolution from H 2 O 2 and H 2 O in native and non-native manganese complexes. It is found that the radical character of the high-valent (PP)Mn(V)OO bond is remarkable, showing the strong potential to generate molecular oxygen because of its high reactivity. The electronic structure and magnetic property of -oxo-bridged manganese porphyrin dimer (PPMn(III)OMn(III)PP) are investigated for further discussion of structure and reactivity of PPMn(X)O (X ϭ II-IV). The potential curve for release of molecular oxygen from PPMn(II)O 2 is also examined to show weak affinity of O 2 in the Mn complex where the oxidation number (X) of Mn is low. Implications of the computational results are also discussed in relation to oxygen evolution reactions.

show abstract

On the mechanisms of aromatic substitution reactions

Cited by 27 publications

References 24 publications

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Effect of the medium on the stereostructure of poly(methyl methacrylate) synthesized in ionic liquids

The electronic structure and magnetic property of metal‐oxo, porphyrin manganese‐oxo, and μ‐oxo‐bridged manganese porphyrin dimer

Contact Info

Product

Resources

About

On the mechanisms of aromatic substitution reactions

Cited by 27 publications

References 24 publications

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn4O5 cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn4O5 cluster of PSII refined to 1.9 Å X‐ray resolution

Effect of the medium on the stereostructure of poly(methyl methacrylate) synthesized in ionic liquids

The electronic structure and magnetic property of metal‐oxo, porphyrin manganese‐oxo, and μ‐oxo‐bridged manganese porphyrin dimer

Contact Info

Product

Resources

About

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution

Possible mechanisms of water splitting reaction based on proton and electron release pathways revealed for CaMn₄O₅ cluster of PSII refined to 1.9 Å X‐ray resolution