Effects of ZSM-5 zeolite confinement on reaction intermediates during dioxygen activation by enclosed dicopper cations

Takashi Yumura, Mina Takeuchi, Hisayoshi Kobayashi, Yasushige Kuroda

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

We investigate how nanospaces surrounded by a 10-membered ring of ZSM-5 zeolite affect the reaction intermediates formed during dioxygen activation by enclosed dicopper cations. Two types of dioxygen intermediates are considered: one is an O2 ⋯ Cu2 complex, where dioxygen binds to the two Cu cations, and the other is a bis(μ-oxo)dicopper complex converted from an O2 ⋯ Cu2 complex by the cleavage of the O-O bond. We employ large-scale density functional theory (DFT) calculations with the B3LYP functional to examine the energetics of the two dioxygen intermediates inside a 10-membered ring of ZSM-5 with double Si → Al substitutions at variable locations. The properties of the O2 ⋯ Cu2 complexes, such as the dioxygen bridging modes and dioxygen activation, are strongly affected by the locations of the two Al atoms within the 10-membered ring. In particular, the O2 ⋯ Cu2 complexes have either end-on or side-on bridging modes depending on the substituted Al positions. On the other hand, the steric hindrances of a ZSM-5 cavity play crucial roles in determining the properties of the bis(μ-oxo)dicopper complexes containing a diamond Cu2O2 core. By restricting its Cu2O2 core to a 10-membered ring of ZSM-5 in which the two Al atoms are second-nearest neighbors, each Cu cation is tetrahedral four-coordinate. On the other hand, the Cu cations have almost square planar coordination inside a ZSM-5 where the Al atoms are fourth-nearest neighbors. The different Cu coordination environments are responsible for the different levels of stability; the planar diamond Cu2O2 core is 30.7 kcal/mol more stable relative to the tetrahedral case. Since the ZSM-5 nanospaces directly influence the stability of the bis(μ-oxo)dicopper complexes by changing the Cu coordination environments, zeolite confinement effects on the bis(μ-oxo)dicopper complexes are more noticeable than those in the O2 ⋯ Cu2 cases. The DFT findings are important in terms of catalytic functions, because the spatial constraint from the ZSM-5 should significantly contribute to the stability of the reaction intermediates formed during the dioxygen activation.

Original languageEnglish
Pages (from-to)508-517
Number of pages10
JournalInorganic Chemistry
Volume48
Issue number2
DOIs
Publication statusPublished - Jan 19 2009

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Reaction intermediates
reaction intermediates
Cations
Chemical activation
activation
Oxygen
cations
rings
diamonds
Diamond
density functional theory
atoms
Atoms
Density functional theory
cleavage
Zeolites
substitutes
cavities
ZSM-5 zeolite
Substitution reactions

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Effects of ZSM-5 zeolite confinement on reaction intermediates during dioxygen activation by enclosed dicopper cations. / Yumura, Takashi; Takeuchi, Mina; Kobayashi, Hisayoshi; Kuroda, Yasushige.

In: Inorganic Chemistry, Vol. 48, No. 2, 19.01.2009, p. 508-517.

Research output: Contribution to journalArticle

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title = "Effects of ZSM-5 zeolite confinement on reaction intermediates during dioxygen activation by enclosed dicopper cations",
abstract = "We investigate how nanospaces surrounded by a 10-membered ring of ZSM-5 zeolite affect the reaction intermediates formed during dioxygen activation by enclosed dicopper cations. Two types of dioxygen intermediates are considered: one is an O2 ⋯ Cu2 complex, where dioxygen binds to the two Cu cations, and the other is a bis(μ-oxo)dicopper complex converted from an O2 ⋯ Cu2 complex by the cleavage of the O-O bond. We employ large-scale density functional theory (DFT) calculations with the B3LYP functional to examine the energetics of the two dioxygen intermediates inside a 10-membered ring of ZSM-5 with double Si → Al substitutions at variable locations. The properties of the O2 ⋯ Cu2 complexes, such as the dioxygen bridging modes and dioxygen activation, are strongly affected by the locations of the two Al atoms within the 10-membered ring. In particular, the O2 ⋯ Cu2 complexes have either end-on or side-on bridging modes depending on the substituted Al positions. On the other hand, the steric hindrances of a ZSM-5 cavity play crucial roles in determining the properties of the bis(μ-oxo)dicopper complexes containing a diamond Cu2O2 core. By restricting its Cu2O2 core to a 10-membered ring of ZSM-5 in which the two Al atoms are second-nearest neighbors, each Cu cation is tetrahedral four-coordinate. On the other hand, the Cu cations have almost square planar coordination inside a ZSM-5 where the Al atoms are fourth-nearest neighbors. The different Cu coordination environments are responsible for the different levels of stability; the planar diamond Cu2O2 core is 30.7 kcal/mol more stable relative to the tetrahedral case. Since the ZSM-5 nanospaces directly influence the stability of the bis(μ-oxo)dicopper complexes by changing the Cu coordination environments, zeolite confinement effects on the bis(μ-oxo)dicopper complexes are more noticeable than those in the O2 ⋯ Cu2 cases. The DFT findings are important in terms of catalytic functions, because the spatial constraint from the ZSM-5 should significantly contribute to the stability of the reaction intermediates formed during the dioxygen activation.",
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T1 - Effects of ZSM-5 zeolite confinement on reaction intermediates during dioxygen activation by enclosed dicopper cations

AU - Yumura, Takashi

AU - Takeuchi, Mina

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AU - Kuroda, Yasushige

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N2 - We investigate how nanospaces surrounded by a 10-membered ring of ZSM-5 zeolite affect the reaction intermediates formed during dioxygen activation by enclosed dicopper cations. Two types of dioxygen intermediates are considered: one is an O2 ⋯ Cu2 complex, where dioxygen binds to the two Cu cations, and the other is a bis(μ-oxo)dicopper complex converted from an O2 ⋯ Cu2 complex by the cleavage of the O-O bond. We employ large-scale density functional theory (DFT) calculations with the B3LYP functional to examine the energetics of the two dioxygen intermediates inside a 10-membered ring of ZSM-5 with double Si → Al substitutions at variable locations. The properties of the O2 ⋯ Cu2 complexes, such as the dioxygen bridging modes and dioxygen activation, are strongly affected by the locations of the two Al atoms within the 10-membered ring. In particular, the O2 ⋯ Cu2 complexes have either end-on or side-on bridging modes depending on the substituted Al positions. On the other hand, the steric hindrances of a ZSM-5 cavity play crucial roles in determining the properties of the bis(μ-oxo)dicopper complexes containing a diamond Cu2O2 core. By restricting its Cu2O2 core to a 10-membered ring of ZSM-5 in which the two Al atoms are second-nearest neighbors, each Cu cation is tetrahedral four-coordinate. On the other hand, the Cu cations have almost square planar coordination inside a ZSM-5 where the Al atoms are fourth-nearest neighbors. The different Cu coordination environments are responsible for the different levels of stability; the planar diamond Cu2O2 core is 30.7 kcal/mol more stable relative to the tetrahedral case. Since the ZSM-5 nanospaces directly influence the stability of the bis(μ-oxo)dicopper complexes by changing the Cu coordination environments, zeolite confinement effects on the bis(μ-oxo)dicopper complexes are more noticeable than those in the O2 ⋯ Cu2 cases. The DFT findings are important in terms of catalytic functions, because the spatial constraint from the ZSM-5 should significantly contribute to the stability of the reaction intermediates formed during the dioxygen activation.

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