MCD spectroscopy of W(V) and Mo(V) dithiolato complexes: Implications for the coordination geometry of the Mo/W active sites of oxotransferases

Oku, Hirosuke; Koehler, Brian P.; Ueyama, Norikazu; Nakamura, Akira; Johnson, Michael K.

doi:10.1016/s0162-0134(97)89897-2

Cited by 2 publications

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“…Energy differences between spectral features provided estimates of the energies (but not the intensities) of ligand−metal charge-transfer transitions from S(π) and S(σ) molecular orbitals to the singly occupied d x 2 - y 2 orbital of product [M V O(mnt) 2 ] - . The latter has been demonstrated to be the HOMO in [Mo V OCl 4 ] - and related species using EPR, absorption, MCD, and photoelectron spectroscopies, as well as calculations based on a variety of theoretical techniques. ,− A range of oxo-tetrathiolatomolybdenum(V) centers [MoO S 4 ] - ( S 4 = tetrathiolato, bis(dithiolato), or bis(dithiolene)) centers have also been studied. − …”

Section: Discussionmentioning

confidence: 99%

“…However, detailed electronic or MCD experimental data are not available to test these predictions as the anion appears to disproportionate in solution . Data are available for the related center [Mo V O(bdt) 2 ] - (bdt = 1,2-benzenedithiolato). ,, Importantly, this anion has also been characterized structurally in the solid state and exhibited C s geometry with one folded dithiolene ligand (θ = 29.5, 10.8°) …”

Section: Discussionmentioning

confidence: 99%

“…The predicted transition energy is close to the experimental value of 1.7 eV and suggests a plausible alternative assignment. On the basis of a comparison of available experimental data, a similar alternative assignment also applies to the equivalent tungsten species (Tables S20 and S30, Figure S12). ,, …”

Section: Discussionmentioning

confidence: 99%

“…32,[57][58][59][60][61][62][63][64] A range of oxo-tetrathiolato-molybdenum(V) centers [MoOS 4 ] -(S 4 ) tetrathiolato, bis-(dithiolato), or bis(dithiolene)) centers have also been studied. [25][26][27][28][29][30][31][32] The eight sulfur-based molecular orbitals S(π) and S(σ) lie directly below the d x 2 -y 2 HOMO and differ in their orientation with respect to the M-S bond vectors and to the valence d-orbitals of metals M (cf, Figure 3). 28,29 The remaining four SALCs derived from S 3p orbitals are involved in S-C(R) covalent bonding and lie at considerably lower energy.…”

Section: Spectral Assignment and Electronic Structures Of [M IV -O(mnt)mentioning

confidence: 99%

“…23,24 The electronic structures of a range of [Mo V OS 4 ] -(d 1 ) species (S 4 ) tetrathiolato, bis(dithiolato), or bis(dithiolene)) have been investigated by a combination of physical and theoretical techniques. [25][26][27][28][29][30][31][32] Intense low-energy transitions in electronic spectra are proposed to involve charge transfer from molecular orbitals of predominantly ligand sulfur character to the highest occupied molecular orbital (HOMO), which is metal-based and essentially nonbonding. [27][28][29][30][31] Photodetachment photoelectron spectroscopy (PES) allows detailed investigation of the electronic structure of gaseous species.…”

Section: Introductionmentioning

confidence: 99%

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Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion

et al. 2004

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Photodetachment photoelectron spectroscopy was used to investigate the electronic structure of the doubly charged complexes [MIVO(mnt)2]2- (M = Mo, W; mnt = 1,2-dicyanoethenedithiolato). These dianions are stable in the gas phase and are minimal models for the active sites of the dimethyl sulfoxide reductase family of molybdenum enzymes and of related tungsten enzymes. Adiabatic and vertical electron binding energies for both species were measured, providing detailed information about molecular orbital energy levels of the parent dianions as well as the ground and excited states of the product anions [MVO(mnt)2]-. Density functional theory calculations were used to assist assignment of the detachment features. Differences in energy between these features provided the energies of ligand-to-metal charge-transfer transitions from S(pi) and S(sigma) molecular orbitals to the singly occupied metal-based orbital of the products [MVO(mnt)2]-. These unique data for the M(V) species were obtained at the C(2)(v)() geometry of the parent M(IV) dianions. However, theoretical calculations and available condensed phase data suggested that a geometry featuring differentially folded dithiolene ligands (Cs point symmetry) was slightly lower in energy. The driving force for ligand folding is a favorable covalent interaction between the singly occupied metal-based molecular orbital (a1 in C2v) point symmetry; highest occupied molecular orbital (HOMO)) and the least stable of the occupied sulfur-based molecular orbitals (b1 in C2v point symmetry, HOMO-1) that is only possible upon reduction to the lower symmetry. This ligand folding induces a large increase in the intensity predicted for the a' S(pi) --> a' dx2 - y2 charge-transfer transition originating from the HOMO-2 of [MVO(mnt)2](-) under Cs point symmetry. Electronic absorption spectra are available for the related species [MoVO(bdt)2]- (bdt = 1,2-benzenedithiolato) and for the oxidized form of dimethyl sulfoxide reductase. The intense absorptions at approximately 1.7 eV have been assigned previously to S(sigma) --> Mo transitions, assuming C2v geometry. The present work indicates that the alternative a' S(pi) --> a' dx2 - y2 of Cs geometry must be considered. Overall, this study confirms that the electronic structure of the M-dithiolene units are exquisitely sensitive to dithiolene ligand folding, reinforcing the proposal that these units are tunable conduits for electron transfer in enzyme systems.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Spectral Assignment and Electronic Structures Of [M IV -O(mnt)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion

et al. 2004

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Molybdenum and Tungsten Enzymes

Stiefel¹,

Pilato²

1999

Bioinorganic Catalysis

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MCD spectroscopy of W(V) and Mo(V) dithiolato complexes: Implications for the coordination geometry of the Mo/W active sites of oxotransferases

Cited by 2 publications

References 0 publications

Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion

Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion

Molybdenum and Tungsten Enzymes

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MCD spectroscopy of W(V) and Mo(V) dithiolato complexes: Implications for the coordination geometry of the Mo/W active sites of oxotransferases

Cited by 2 publications

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Photoelectron Spectroscopy of the Doubly-Charged Anions [MIVO(mnt)2]2- (M = Mo, W; mnt = S2C2(CN)22-): Access to the Ground and Excited States of the [MVO(mnt)2]- Anion

Photoelectron Spectroscopy of the Doubly-Charged Anions [MIVO(mnt)2]2- (M = Mo, W; mnt = S2C2(CN)22-): Access to the Ground and Excited States of the [MVO(mnt)2]- Anion

Molybdenum and Tungsten Enzymes

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Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion

Photoelectron Spectroscopy of the Doubly-Charged Anions [M^IVO(mnt)₂]²^- (M = Mo, W; mnt = S₂C₂(CN)₂²^-): Access to the Ground and Excited States of the [M^VO(mnt)₂]^- Anion