Multielectron photochemistry of quadruply bonded metal-metal complexes

Partigianoni, Colleen M.; Chang, I-Cheng; Nocera, Daniel G.

doi:10.1016/0010-8545(90)80083-6

Cited by 22 publications

(24 citation statements)

References 20 publications

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“…PARTIGIANONI ET AL. Photoredox Chemistry of d 4 Bimetallic Systems 151 focused on the diphenylphosphate complex Mo 2 [0 2 P(OC 6 H 5 )2] 4 , which displays weak luminescence (<£ em ~5 χ 10" 4 ) in nonaqueous solutions and a sufficiently long lifetime (r 0 = 68 ns) to permit excited-state reaction upon S δ* excitation (34,35). For example, the two-electron conversion of 1,2-dichloroethane (DCE) to ethylene and the mixed-valence Mo 2 (II,III) complex is promoted by visible light according to the reaction…”

Section: Metal-organic Photochemistry Of D Bimetallic Phosphatmentioning

confidence: 99%

“…In addition the parent ion cluster of W 2 Cl 5 (dppm) 2 I at 1441 amu is also observed in the FABMS of the photoproduct. This pentac^oro product is a signature of the free radical photoreactions of M^1 4 (P P) 2 complex^ We have accounted for the formation of M 2 C1 5 (P P) 2 X and^jj^Cl^P P) 2 X 2 products with a radical mechanism wherein the M 2 C1 4 (P P) 2 _çomplex photoreacts with substrate to produce a mixed-valence M 2 C1 4 (P P) 2 X primary photoproduct (eq 3) that disproportionates by either chlorine (eq 4) or X atom (eq 5) transfer (35,62).…”

Section: Metal-organic Photochemistry Of M 2 Cl 4 (Diphenylphosphinommentioning

confidence: 99%

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Photoredox Chemistry of d⁴ Bimetallic Systems

Partigianoni

Turró

Hsu

et al. 1993

Photosensitive Metal—Organic Systems

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Section: Metal-organic Photochemistry Of D Bimetallic Phosphatmentioning

confidence: 99%

Section: Metal-organic Photochemistry Of M 2 Cl 4 (Diphenylphosphinommentioning

confidence: 99%

Photoredox Chemistry of d⁴ Bimetallic Systems

Partigianoni

Turró

Hsu

et al. 1993

Photosensitive Metal—Organic Systems

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“…25−27 The excited states are highly reductive and capable of reducing 1,2-dichloroethane to ethylene in organic solvents, whereas the Mo 2 core remains undamaged. 28 The photoreaction is metal centered in terms of electronic transition between the ground and excited states, different from mononuclear transition metal complexes in nature. 29 A paddlewheel Mo 2 complex has an electronic configuration of σ 2 π 4 δ 2 ground state, as described in Figure 1, with two d electrons paired in the high-energy bonding orbital (δ).…”

Section: ■ Introductionmentioning

confidence: 99%

“…32 The multiply bonded Mo 2 complexes may act as an electron source or sink, depending on its oxidation state or bond order, in the oxidation−reduction process by providing or accepting electrons accompanied with δ bond breakage or formation. 33,28 In nonaqueous solutions, the singlet δδ* excited state has sufficiently long lifetime to participate in photochemical reactions, 34,35 unlike single metal complexes whose long-lived excited state results from intersystem conversion that reduces the quantum efficiency. Furthermore, Mo 2 complexes are usually coordinatively unsaturated with two vacant axial positions, which are prepared for coordination of substrate molecules.…”

Section: ■ Introductionmentioning

confidence: 99%

Making Use of the δ Electrons in K₄Mo₂(SO₄)₄ for Visible-Light-Induced Photocatalytic Hydrogen Production

Liu

Zhu

et al. 2019

ACS Appl. Mater. Interfaces

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Quadruply bonded dimolybdenum complexes with a σ 2 π 4 δ 2 electronic configuration for the ground state have rich metal-centered photochemistry. An earlier study showed that stoichiometric or less amount of molecular hydrogen was produced upon irradiation by ultraviolet light (λ = 254 nm) of K 4 Mo 2 (SO 4 ) 4 in sulfuric acid solution, which was attributed to the reductive capability of the ππ* excited state. To make use of the δ electrons for visible-light-induced photocatalytic hydrogen evolution, a multicomponent heterogeneous photocatalytic system containing K 4 Mo 2 (SO 4 ) 4 photosensitizer, TiO 2 electron relay, and MoS 2 cocatalyst is designed and tested. With ascorbic acid added as a sacrificial reagent, irradiation by artificial sunlight (AM 1.5) on the reaction in 5 M H 2 SO 4 has produced 13 400 μmol g −1 of molecular hydrogen (based on the Mo 2 complex), which is 30 times higher than the hydrogen yield obtained from the reaction of bare K 4 Mo 2 (SO 4 ) 4 with H 2 SO 4 under ultraviolet light irradiation. Further improvement of hydrogen evolution is achieved by addition of oxalic acid, along with an electron donor, which gives an additional 50% increase in H 2 yield. Spectroscopic analyses indicate that, in this case, a junction between the Mo 2 complex and TiO 2 is built by the oxalate bridging ligand, which facilitates charge injection and separation from the Mo 2 core. This Mo 2 −TiO 2 −MoS 2 system has achieved a high hydrogen evolution rate up to 4570 μmol g −1 h −1 . The efficiency of K 4 Mo 2 (SO 4 ) 4 as a metal-centered photosensitizer is also proved by parallel experiments with a dye chromophore, fluorescein, which presents comparable H 2 yields and hydrogen evolution rates. Most importantly, in this study, detailed analyses illustrate that the photocatalytic cycle with hydrogen gas as an outcome of the reaction is established by involvement of the δδ* excited state generated by visible light irradiation. Therefore, this work shows the potential of quadruply bonded Mo 2 complexes as photosensitizers for photocatalytic hydrogen evolution.

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“…Finally, beyond its importance in models for chemical bonding, the zwitterionic excited-state manifold has important ramifications on chemical reactivity owing to the pairing of two electrons on one center and two holes on an adjacent one. This species is predisposed to multielectron reactivity and explains the photochemistry of M L M complexes (27). More generally, zwitterionic states may prove to be critical intermediates in strategies to effect multielectron transformations in biology and chemistry.…”

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confidence: 98%

Direct Spectroscopic Detection of a Zwitterionic Excited State

Engebretson

Zaleski

Leroi

et al. 1994

Science

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Two electrons in two weakly coupled orbitals give rise to two states (diradical) with electrons residing in separate orbitals and two states (zwitterionic) with both electrons paired in one orbital or the other. This two-electron, two-orbital state manifold has eluded experimental confirmation because the zwitterionic states have been difficult to locate. Two-photon excitation of fluorescence from Mo(2)CI(4)(PMe(3))(4) (D2d) has been measured with linearly and circularly polarized light. From the polarization ratio and the energy of the observed transition, the 2(1)A(1) (delta*delta*) excited state has been located and characterized. In conjunction with the one-photon allowed (1)B(2) (deltadelta*) excited state, the zwitterionic state manifold for the quadruply bonded metal-metal class of compounds is thus established.

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Multielectron photochemistry of quadruply bonded metal-metal complexes

Cited by 22 publications

References 20 publications

Photoredox Chemistry of d⁴ Bimetallic Systems

Photoredox Chemistry of d⁴ Bimetallic Systems

Making Use of the δ Electrons in K₄Mo₂(SO₄)₄ for Visible-Light-Induced Photocatalytic Hydrogen Production

Direct Spectroscopic Detection of a Zwitterionic Excited State

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Multielectron photochemistry of quadruply bonded metal-metal complexes

Cited by 22 publications

References 20 publications

Photoredox Chemistry of d4 Bimetallic Systems

Photoredox Chemistry of d4 Bimetallic Systems

Making Use of the δ Electrons in K4Mo2(SO4)4 for Visible-Light-Induced Photocatalytic Hydrogen Production

Direct Spectroscopic Detection of a Zwitterionic Excited State

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Product

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About

Photoredox Chemistry of d⁴ Bimetallic Systems

Photoredox Chemistry of d⁴ Bimetallic Systems

Making Use of the δ Electrons in K₄Mo₂(SO₄)₄ for Visible-Light-Induced Photocatalytic Hydrogen Production