Characterization of metal-oxygen bridge systems

Wing, Richard M.; Callahan, Kenneth P.

doi:10.1021/ic50074a034

Cited by 111 publications

(45 citation statements)

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“…The observed high intensity of the 456 cm Ϫ1 isotope sensitive vibration in Fig. 1 supports its assignment as the symmetric stretch of an oxo group bridging two Cu centers (21). The weak 870 cm Ϫ1 vibration is then assigned as an antisymmetric metal-oxo stretch ( as ), which should not be enhanced in the rR spectrum, while its second quantum (2 as ) is symmetric and consequently would have higher rR intensity than the fundamental, as observed for the 1,725 cm Ϫ1 vibration.…”

Section: Resultssupporting

confidence: 59%

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Woertink

Smeets

Groothaert

et al. 2009

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

595

653

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Driven by the depletion of crude oil, the direct oxidation of methane to methanol has been of considerable interest. Promising low-temperature activity of an oxygen-activated zeolite, Cu-ZSM-5, has recently been reported in this selective oxidation and the active site in this reaction correlates with an absorption feature at 22,700 cm ؊1 . In the present study, this absorption band is used to selectively resonance enhance Raman vibrations of this active site. 18 O2 labeling experiments allow definitive assignment of the observed vibrations and exclude all previously characterized copper-oxygen species for the active site. In combination with DFT and normal coordinate analysis calculations, the oxygen activated Cu core is uniquely defined as a bent mono-( -oxo)dicupric site. Spectroscopically validated electronic structure calculations show polarization of the low-lying singly-occupied molecular orbital of the [Cu 2O] 2؉ core, which is directed into the zeolite channel, upon approach of CH 4. This induces significant oxyl character into the bridging O atom leading to a low transition state energy consistent with experiment and explains why the bent mono-( -oxo)dicupric core is highly activated for H atom abstraction from CH 4. The oxygen intermediate of Cu-ZSM-5 is now the most well defined species active in the methane monooxygenase reaction. density functional theory ͉ dicopper(II)-oxo ͉ oxygen activation ͉ resonance Raman spectroscopy ͉ zeolite

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Section: Resultssupporting

confidence: 59%

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Woertink

Smeets

Groothaert

et al. 2009

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

595

653

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“…Figure 3 shows the FTIR spectra of the products compared with the Fe-PPIX-Cl monomer and PPIX. Of interest is the feature at ≈ 840 cm −1 which has previously been attributed to the asymmetric stretch of the Fe-O-Fe bridge [12][13][14][15]. The fact that both PPIX and Fe-PPIX-Cl exhibit absorption in this region is an indication that these vibrational modes originate from the porphyrin ring, however.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

Dziedzic-Kocurek

Byrne²,

Swiderski

et al. 2009

Acta Phys. Pol. A

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The commercial protoporphyrin IX, iron-ferriprotoporphyrin IX-chloride and synthesized iron porphyrin µ-oxo-dimers were examined by UV/vis absorption and fluorescence, Fourier transformed infrared spectroscopy, resonance Raman, X-ray absorption, Mössbauer spectroscopy and SQUID. The evidence of Fe-O-Fe antiferromagnetic coupling concluded from SQUID and Mössbauer in the case of samples containing dimerized forms confirmed the presence of the oxo-bridges. In this paper the results of UV/vis, fluorescence, Fourier transform infrared FTIR and Raman spectroscopies are reported and discussed. The study is based on the comparison of the free-base protoporphyrin IX, Fe-PPIX-Cl and the synthesized dimerized specimen. The vibrational modes in two energy regions i.e. 330-650 cm −1 and 750-900 cm −1 , reportedly characteristic of the existence of Fe-O-Fe bridges, are discussed. A significant photoluminescence emission, strongly Stokes shifted from the Soret band, absent in the protoporphyrin IX and the iron-ferriprotoporphyrin IX-chloride, is observed. The strong Stokes shift and the mismatch of the excitation spectrum to the Soret band suggest that is does not have origin in the de-excitation of the porphyrin moiety and that it could have origin in an Fe-O-Fe charge transfer state.

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“…[54] This band is systematically accompanied by a broad and weaker one, which has been attributed to its first overtone 2ν sym at twice the energy. [74,75] The Raman spectrum of compound 1 displays a relatively intense and narrow band at 289 cm -1 , which does not appear in the spectra of K 7 [73] but is impossible to be distinguished from the ν W=Ot and ν W-O-W bands, if not too weak to be observed. In addition this spectrum shows two wellseparated bands at higher energy (1089 and 1038 cm -1 ) attributed to the {P=O} vibrators.…”

Section: P and 183 W Nmr Spectroscopymentioning

confidence: 95%

Hydrothermal Synthesis and Structural Characterization of the High‐Valent Ruthenium‐Containing Polyoxoanion [{PW₁₁O₃₉}₂{(HO)Ru^IV–O–Ru^IV(OH)}]^10–

Chen

Villanneau

et al. 2008

Eur J Inorg Chem

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The high‐valent ruthenium‐containing [{PW11O39}2{(HO)RuIV–O–RuIV(OH)}]10– anion (1) has been synthesized by hydrothermal reaction and characterized by X‐ray diffraction, IR, multinuclear (31P and 183W) NMR spectroscopy andelectrochemistry. Single‐crystal analysis was carried outon Rb10[{PW11O39}2{(HO)RuIV–O–RuIV(OH)}]·21H2O, which crystallizes in the monoclinic system, space group P21/n, with a = 11.1912(14), b = 21.9257(12), c = 38.7310(96) Å, β = 94.682(19)°, V = 9472(3) Å3, Z = 4. Polyanion 1 consists of two lacunary [α‐PW11O39]7– anions connected by a linear {(HO)Ru–O–Ru(OH)}4+ unit. Each ruthenium ion achieves six‐coordination through interaction with two terminal oxo ligands from the lacuna of each [PW11O39]7– anion.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Characterization of metal-oxygen bridge systems

Cited by 111 publications

References 0 publications

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

Hydrothermal Synthesis and Structural Characterization of the High‐Valent Ruthenium‐Containing Polyoxoanion [{PW₁₁O₃₉}₂{(HO)Ru^IV–O–Ru^IV(OH)}]^10–

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Characterization of metal-oxygen bridge systems

Cited by 111 publications

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A [Cu 2 O] 2+ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

A [Cu 2 O] 2+ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

Hydrothermal Synthesis and Structural Characterization of the High‐Valent Ruthenium‐Containing Polyoxoanion [{PW11O39}2{(HO)RuIV–O–RuIV(OH)}]10–

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A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Hydrothermal Synthesis and Structural Characterization of the High‐Valent Ruthenium‐Containing Polyoxoanion [{PW₁₁O₃₉}₂{(HO)Ru^IV–O–Ru^IV(OH)}]^10–