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