A Valence Bond Description of Dizwitterionic Dithiolene Character in an Oxomolybdenum–Bis(dithione) Complex

Mtei, Regina P.; Perera, Eranda; Mogesa, Benjamin; Stein, Benjamin W.; Basu, Partha; Kirk, Martin L.

doi:10.1002/ejic.201101084

Cited by 24 publications

(34 citation statements)

References 16 publications

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“…We have shown that these ring systems, in conjunction with the dithiolene, afford additional redox possibilities and these may play a role in the enzymes. 20,31,32 Interestingly, the Mo(IV)-dithione/Mo(VI)-dithiolene couple constitute a valence tautomeric system. Thus, the determination of Mo and dithiolene oxidation states from molybdoenzyme protein crystallography may not straightforward if the pyranopterin dithiolene chelate in the enzymes can exist in different oxidation states.…”

Section: Discussionmentioning

confidence: 99%

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Large Ligand Folding Distortion in an Oxomolybdenum Donor–Acceptor Complex

et al. 2015

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Interligand charge transfer is examined in the novel metallo-dithiolene complex MoO(SPh)2(iPr2Dto) (where iPr2Dto is N,N′-isopropyl-piperazine-2,3-dithione). The title complex displays a remarkable 70° “envelope” type fold of the five member dithiolene ring, which is bent upward toward the terminal oxo ligand. A combination of electronic absorption and resonance Raman spectroscopies have been used to probe the basic electronic structure responsible for the large fold-angle distortion. The intense charge transfer transition observed at ~18,000 cm−1 is assigned as a thiolate → dithione ligand-to-ligand charge transfer (LL′CT) transition that also possesses Mo(IV) → dithione charge transfer character. Strong orbital mixing between occupied and virtual orbitals with Mo(x2−y2) orbital character derives from a strong pseudo Jahn-Teller effect, which drives the large fold angle distortion to yield a double well potential in the electronic ground state.

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Section: Discussionmentioning

confidence: 99%

“…N,N′-diisopropyl piperazine 2,3-dithione ( i Pr 2 Dt o ) and [MoOCl( i Pr 2 Dt o ) 2 ][PF 6 ] were synthesized according to literature procedures. 20 …”

Section: Methodsmentioning

confidence: 99%

Large Ligand Folding Distortion in an Oxomolybdenum Donor–Acceptor Complex

et al. 2015

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“…Dithiolenes display remarkable non-innocent behavior in small molecule analogues of pyranopterin Mo active sites (9)(10)(11). This non-innocence extends the redox cycling of the metal through its VI/V/IV oxidation states to include two electron redox reactions of the dithiolene ligand via access to the reduced ene-dithiolate, radical dithiolene, and oxidized dithione forms (12)(13)(14).…”

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Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Rothery

Stein

Solomonson

et al. 2012

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

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We have analyzed the conformations of 319 pyranopterins in 102 protein structures of mononuclear molybdenum and tungsten enzymes. These span a continuum between geometries anticipated for quinonoid dihydro, tetrahydro, and dihydro oxidation states. We demonstrate that pyranopterin conformation is correlated with the protein folds defining the three major mononuclear molybdenum and tungsten enzyme families, and that binding-site microtuning controls pyranopterin oxidation state. Enzymes belonging to the bacterial dimethyl sulfoxide reductase (DMSOR) family contain a metal-bis-pyranopterin cofactor, the two pyranopterins of which have distinct conformations, with one similar to the predicted tetrahydro form, and the other similar to the predicted dihydro form. Enzymes containing a single pyranopterin belong to either the xanthine dehydrogenase (XDH) or sulfite oxidase (SUOX) families, and these have pyranopterin conformations similar to those predicted for tetrahydro and dihydro forms, respectively. This work provides keen insight into the roles of pyranopterin conformation and oxidation state in catalysis, redox potential modulation of the metal site, and catalytic function.energetics | molybdoenzymes | redox chemistry T he pyranopterin dithiolene ligand is present in all molybdenum (Mo) and tungsten (W) containing enzymes with the exception of nitrogenase (1). These enzymes, known as mononuclear Mo/W enzymes, play pivotal roles in metabolism, global geochemical cycles, and microbial metabolic diversity (2-5). Their active sites, comprising a Mo or W ion and one or two pyranopterins, catalyze a diversity of redox transformations spanning a reduction potential range of approximately one volt. While the immediate environment of the substrate-binding metal ion is critically important in catalysis (6), little attention has been focused on the impact of variations in pyranopterin structure on enzyme function.Protein-bound pyranopterins are typically interpreted as having the tricyclic structure depicted in Fig. 1A, comprising pyrimidine, piperazine, and pyran-dithiolene rings. The dithiolene chelate binds a single Mo/W atom, which constitutes the catalytic active site. The pyranopterin shown in Fig. 1A is also known as the tetrahydro mononucleotide form due to the oxidation state of its piperazine ring and the presence of a phosphomethyl group attached to its C-2 atom (1). This form is assigned to the xanthine dehydrogenases, and in its cytosine dinucleotide form to the bacterial carbon monoxide dehydrogenases and aldehyde dehydrogenases (these enzymes are referred to collectively as the XDH family). It is also assigned to the sulfite oxidases and plant nitrate reductases [SUOX family (1, 5)].Mononuclear Mo/W enzymes also coordinate metal-bis-pyranopterin cofactors, either as the metal-bis(pyranopterin guanine dinucleotide) form (Fig. 1D) found in the dimethyl sulfoxide reductase family of molybdoenzyme subunits (DMSOR family), or the mononuclear bis-pyranopterin form found in the thermophilic aldehyde oxidoreductases...

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“…7b). 57 This was the first time a dithiolene backbone has been quantified in terms of different resonance contributions.…”

Section: Models Illustrating the Role Of Dithiolene Redoxmentioning

confidence: 99%

Recent developments in the study of molybdoenzyme models

Basu

Burgmayer

2015

J Biol Inorg Chem

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Over the past two decades a plethora of crystal structures of molybdenum enzymes has appeared in the literature providing a clearer picture of the enzymatic active sites and increasing the challenge to chemists to develop accurate models for those sites. In this minireview we discuss the most recent model studies aimed to reproduce detailed features of the pterin-dithiolene ligand, both as the uncoordinated form and as a chelate coordinated to molybdenum.

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A Valence Bond Description of Dizwitterionic Dithiolene Character in an Oxomolybdenum–Bis(dithione) Complex

Cited by 24 publications

References 16 publications

Large Ligand Folding Distortion in an Oxomolybdenum Donor–Acceptor Complex

Large Ligand Folding Distortion in an Oxomolybdenum Donor–Acceptor Complex

Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Recent developments in the study of molybdoenzyme models

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