Dataset Information

Deconvoluting the Innocent vs. Non-innocent Behavior of N,N-diethylphenylazothioformamide Ligands with Copper Sources.

ABSTRACT: Redox-active ligands lead to ambiguity in often clearly defined oxidation states of both the metal centre and the ligand. The arylazothioformamide (ATF) ligand class represents a redox-active ligand with three possible redox states (neutral, singly reduced, and doubly reduced). ATF-metal interactions result in strong colorimetric transitions allowing for the use of ATFs in metal detection and/or separations. While previous reports have discussed dissolution of zerovalent metals, the resulting oxidation states of coordination complexes have proved difficult to interpret through X-ray crystallographic analysis alone. This report describes the X-ray crystallographic analysis combined with computational modelling of the ATF ligand and metal complexes to deconvolute the metal and ligand oxidation state of metal-ATF complexes. Metal(ATF)2 complexes that originated from zerovalent metals were found to exist as dicationic metal centers containing two singly reduced ATF ligands. When employing Cu(I) salts instead of Cu(0) to generate copper-ATF complexes, the resulting complexes remained Cu(I) and the ATF ligand remained "innocent", existing in its neutral state. Although the use of CuX (where X = Br or I) or [Cu(NCMe)4]Y (where Y = BF4 or PF6) generated species of the type: [(ATF)Cu(?-X)]2 and [Cu(ATF)2]Y, respectively, the ATF ligand remained in its neutral state for each species type.

SUBMITTER: Johnson NA

PROVIDER: S-EPMC6217847 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Publications

Deconvoluting the Innocent vs. Non-innocent Behavior of <i>N,N</i>-diethylphenylazothioformamide Ligands with Copper Sources.

Johnson Nicolas A NA Wolfe Samuel R SR Kabir Humayun H Andrade Gabriel A GA Yap Glenn P A GPA Heiden Zachariah M ZM Moberly James G JG Roll Mark F MF Waynant Kristopher V KV

European journal of inorganic chemistry 20171126 47

Redox-active ligands lead to ambiguity in often clearly defined oxidation states of both the metal centre and the ligand. The arylazothioformamide (ATF) ligand class represents a redox-active ligand with three possible redox states (neutral, singly reduced, and doubly reduced). ATF-metal interactions result in strong colorimetric transitions allowing for the use of ATFs in metal detection and/or separations. While previous reports have discussed dissolution of zerovalent metals, the resulting ox ...[more]

PMID: 30410418

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Project description:The complex [TEA][Tp*MoIV(O)(S2BMOPP)] (1) [TEA = tetraethylammonium, Tp* = tris(3,5-dimethylpyrazolyl)hydroborate, and BMOPP = 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl pterin] is a structural analogue of the molybdenum cofactor common to all pyranopterin molybdenum enzymes because it possesses a pyranopterin-ene-1,2-dithiolate ligand (S2BMOPP) that exists primarily in the ring-closed pyrano structure as a resonance hybrid of ene-dithiolate and thione-thiolate forms. Compound 1, the protonated [Tp*MoIV(O)(S2BMOPP-H)] (1-H) and one-electron-oxidized [Tp*MoV(O)(S2BMOPP)] [1-Mo(5+)] species have been studied using a combination of electrochemistry, electronic absorption, and electron paramagnetic resonance (EPR) spectroscopy. Additional insight into the nature of these molecules has been derived from electronic structure computations. Differences in dithiolene C-S bond lengths correlate with relative contributions from both ene-dithiolate and thione-thiolate resonance structures. Upon protonation of 1 to form 1-H, large spectroscopic changes are observed with transitions assigned as Mo(xy) → pyranopterin metal-to-ligand charge transfer and dithiolene → pyranopterin intraligand charge transfer, respectively, and this underscores a dramatic change in electronic structure between 1 and 1-H. The changes in electronic structure that occur upon protonation of 1 are also reflected in a large >300 mV increase in the Mo(V/IV) redox potential for 1-H, resulting from the greater thione-thiolate resonance contribution and decreased charge donation that stabilize the Mo(IV) state in 1-H with respect to one-electron oxidation. EPR spin Hamiltonian parameters for one-electron-oxidized 1-Mo(5+) and uncyclized [Tp*MoV(O)(S2BDMPP)] [3-Mo(5+)] [BDMPP = 6-(3-butynyl-2,2-dimethyl)-2-pivaloyl pterin] are very similar to each other and to those of [Tp*MoVO(bdt)] (bdt = 1,2-ene-dithiolate). This indicates that the dithiolate form of the ligand dominates at the Mo(V) level, consistent with the demand for greater S → Mo charge donation and a corresponding increase in Mo-S covalency as the oxidation state of the metal is increased. Protonation of 1 represents a simple reaction that models how the transfer of a proton from neighboring acidic amino acid residues to the Mo cofactor at a nitrogen atom within the pyranopterin dithiolene (PDT) ligand in pyranopterin molybdenum enzymes can impact the electronic structure of the Mo-PDT unit. This work also illustrates how pyran ring-chain tautomerization drives changes in resonance contributions to the dithiolene chelate and may adjust the reduction potential of the Mo ion.

Dataset Information

Deconvoluting the Innocent vs. Non-innocent Behavior of N,N-diethylphenylazothioformamide Ligands with Copper Sources.

Publications

Deconvoluting the Innocent vs. Non-innocent Behavior of <i>N,N</i>-diethylphenylazothioformamide Ligands with Copper Sources.

Similar Datasets

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