6 research outputs found

    Variable Nitric Oxide Reactivity of Tropocoronand Cobalt(III) Nitrite Complexes as a Function of the Polymethylene Linker Chain Length

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    The size-dependent reactivity of cobalt tropocoronands [TC-<i>n</i>,<i>n</i>]<sup>2–</sup> is manifest in the NO chemistry of the cobalt­(III) nitrite complexes [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-<i>n</i>,<i>n</i>)] (<i>n</i> = 4–6), the synthesis and characterization of which are reported for the first time. Complete conversion of [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-4,4)] to the cobalt mononitrosyl [Co­(NO)­(TC-4,4)] occurs upon exposure to NO­(g). In contrast, addition of NO­(g) to [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-5,5)] generates both cobalt mono- and dinitrosyl adducts, and addition of nitric oxide to [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-6,6)] converts this complex to the dicobalt tetranitrosyl species [Co<sub>2</sub>(NO)<sub>4</sub>(TC-6,6)]. In the latter complex, two tetrahedral cobalt dinitrosyl units are bound to the aminotroponeiminate poles of the [TC-6,6]<sup>2–</sup> ligand. These results significantly broaden the chemistry of cobalt tropocoronands with nitric oxide and the nitrite anion

    Variable Nitric Oxide Reactivity of Tropocoronand Cobalt(III) Nitrite Complexes as a Function of the Polymethylene Linker Chain Length

    No full text
    The size-dependent reactivity of cobalt tropocoronands [TC-<i>n</i>,<i>n</i>]<sup>2–</sup> is manifest in the NO chemistry of the cobalt­(III) nitrite complexes [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-<i>n</i>,<i>n</i>)] (<i>n</i> = 4–6), the synthesis and characterization of which are reported for the first time. Complete conversion of [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-4,4)] to the cobalt mononitrosyl [Co­(NO)­(TC-4,4)] occurs upon exposure to NO­(g). In contrast, addition of NO­(g) to [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-5,5)] generates both cobalt mono- and dinitrosyl adducts, and addition of nitric oxide to [Co­(η<sup>2</sup>-NO<sub>2</sub>)­(TC-6,6)] converts this complex to the dicobalt tetranitrosyl species [Co<sub>2</sub>(NO)<sub>4</sub>(TC-6,6)]. In the latter complex, two tetrahedral cobalt dinitrosyl units are bound to the aminotroponeiminate poles of the [TC-6,6]<sup>2–</sup> ligand. These results significantly broaden the chemistry of cobalt tropocoronands with nitric oxide and the nitrite anion

    Influence of Tetraazamacrocyclic Ligands on the Nitric Oxide Reactivity of their Cobalt(II) Complexes

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    The reactions of cobalt­(II) complexes of tetraazamacrocyclic tropocoronand (TC) ligands with nitric oxide (NO) were investigated. When [Co­(TC-5,5)] was allowed to react with NO­(g), the {CoNO}<sup>8</sup> mononitrosyl [Co­(NO)­(TC-5,5)] was isolated and structurally characterized. In contrast, a {Co­(NO)<sub>2</sub>}<sup>10</sup> species formed when [Co­(TC-6,6)] was exposed to NO­(g), and the nitrito [Co­(NO<sub>2</sub>)­(TC-6,6)] complex was structurally and spectroscopically characterized from the reaction mixture. The {Co­(NO)<sub>2</sub>}<sup>10</sup> species was assigned as the bis­(cobalt dinitrosyl) complex [Co<sub>2</sub>(NO)<sub>4</sub>(TC-6,6)] by spectroscopic comparison with independently synthesized and characterized material. These results provide the first evidence for the influence of tropocoronand ring size on the nitric oxide reactivity of the cobalt­(II) complexes

    Zinc Thiolate Reactivity toward Nitrogen Oxides: Insights into the Interaction of Zn<sup>2+</sup> with <i>S</i>-Nitrosothiols and Implications for Nitric Oxide Synthase

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    Zinc thiolate complexes containing N<sub>2</sub>S tridentate ligands were prepared to investigate their reactivity toward reactive nitrogen species, chemistry proposed to occur at the zinc tetracysteine thiolate site of nitric oxide synthase (NOS). The complexes are unreactive toward nitric oxide (NO) in the absence of dioxygen, strongly indicating that NO cannot be the species directly responsible for <i>S</i>-nitrosothiol formation and loss of Zn<sup>2+</sup> at the NOS dimer interface in vivo. <i>S</i>-Nitrosothiol formation does occur upon exposure of zinc thiolate solutions to NO in the presence of air, however, or to NO<sub>2</sub> or NOBF<sub>4</sub>, indicating that these reactive nitrogen/oxygen species are capable of liberating zinc from the enzyme, possibly through generation of the <i>S</i>-nitrosothiol. Interaction between simple Zn<sup>2+</sup> salts and preformed <i>S</i>-nitrosothiols leads to decomposition of the −SNO moiety, resulting in release of gaseous NO and N<sub>2</sub>O. The potential biological relevance of this chemistry is discussed

    Influence of Tetraazamacrocyclic Ligands on the Nitric Oxide Reactivity of their Cobalt(II) Complexes

    No full text
    The reactions of cobalt­(II) complexes of tetraazamacrocyclic tropocoronand (TC) ligands with nitric oxide (NO) were investigated. When [Co­(TC-5,5)] was allowed to react with NO­(g), the {CoNO}<sup>8</sup> mononitrosyl [Co­(NO)­(TC-5,5)] was isolated and structurally characterized. In contrast, a {Co­(NO)<sub>2</sub>}<sup>10</sup> species formed when [Co­(TC-6,6)] was exposed to NO­(g), and the nitrito [Co­(NO<sub>2</sub>)­(TC-6,6)] complex was structurally and spectroscopically characterized from the reaction mixture. The {Co­(NO)<sub>2</sub>}<sup>10</sup> species was assigned as the bis­(cobalt dinitrosyl) complex [Co<sub>2</sub>(NO)<sub>4</sub>(TC-6,6)] by spectroscopic comparison with independently synthesized and characterized material. These results provide the first evidence for the influence of tropocoronand ring size on the nitric oxide reactivity of the cobalt­(II) complexes

    Reactions of Organozinc Thiolates with Nitrosonium Ion: <i>C</i>‑Nitroso Formation by Possible Transnitrosation

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    The organometallic complexes [ZnPAThEt] and [ZnPAThMes], where PATh is 2-methyl-1-[methyl-(2-pyridin-2-yl-ethyl)­amino]­propane-2-thiolate, were prepared and their reactions with NOBF<sub>4</sub> investigated. Formation of <i>C</i>-nitrosoethane and <i>C</i>-nitrosomesitylene, respectively, was established, and structural characterization of the latter by X-ray crystallography conclusively proved the dimeric nature of [MesNO]<sub>2</sub> in the solid state. A transnitrosation pathway for <i>C</i>-nitroso formation is proposed based on theoretical calculations
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