4 research outputs found
Insight into the Reactivity and Electronic Structure of Dinuclear Dinitrosyl Iron Complexes
A combination of N/S/Fe K-edge X-ray
absorption spectroscopy (XAS), X-ray diffraction data, and density
functional theory (DFT) calculations provides an efficient way to
unambiguously delineate the electronic structures and bonding characters
of Fe–S, N–O, and Fe–N bonds among the direduced-form
Roussin’s red ester (RRE) [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>]<sup>2–</sup>(<b>1</b>) with
{FeÂ(NO)<sub>2</sub>}<sup>10</sup>-{FeÂ(NO)<sub>2</sub>}<sup>10</sup> core, the reduced-form RRE [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>]<sup>−</sup>(<b>3</b>) with {FeÂ(NO)<sub>2</sub>}<sup>9</sup>-{FeÂ(NO)<sub>2</sub>}<sup>10</sup> core, and
RRE [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>] (<b>4</b>) with {FeÂ(NO)<sub>2</sub>}<sup>9</sup>-{FeÂ(NO)<sub>2</sub>}<sup>9</sup> core. The major contributions of highest occupied molecular
orbital (HOMO) 113α/β in complex <b>1</b> is related
to the antibonding character between FeÂ(d) and FeÂ(d), FeÂ(d), and S
atoms, and bonding character between FeÂ(d) and NOÂ(Ï€*). The effective
nuclear charge (<i><i>Z</i></i><sub>eff</sub>)
of Fe site can be increased by removing electrons from HOMO to shorten
the distances of Fe···Fe and Fe–S from <b>1</b> to <b>3</b> to <b>4</b> or, in contrast, to
increase the Fe–N bond lengths from <b>1</b> to <b>3</b> to <b>4</b>. The higher IR ν<sub>NO</sub> stretching
frequencies (1761, 1720 cm<sup>–1</sup> (<b>4</b>), 1680,
1665 cm<sup>–1</sup> (<b>3</b>), and 1646, 1611, 1603
cm<sup>–1</sup> (<b>1</b>)) associated with the higher
transition energy of N<sub>1s</sub> →σ*Â(NO) (412.6 eV
(<b>4</b>), 412.3 eV (<b>3</b>), and 412.2 eV (<b>1</b>)) and the higher <i><i>Z</i></i><sub>eff</sub> of Fe derived from the transition energy of Fe<sub>1s</sub> →
Fe<sub>3d</sub> (7113.8 eV (<b>4</b>), 7113.5 eV (<b>3</b>), and 7113.3 eV (<b>1</b>)) indicate that the N–O bond
distances of these complexes are in the order of <b>1 > 3 >
4</b>. The N/S/Fe K-edge XAS spectra as well as DFT computations
reveal the reduction of complex <b>4</b> yielding complex <b>3</b> occurs at Fe, S, and NO; in contrast, reduction mainly occurs
at Fe site from complex <b>3</b> to complex <b>1</b>
Insight into the Reactivity and Electronic Structure of Dinuclear Dinitrosyl Iron Complexes
A combination of N/S/Fe K-edge X-ray
absorption spectroscopy (XAS), X-ray diffraction data, and density
functional theory (DFT) calculations provides an efficient way to
unambiguously delineate the electronic structures and bonding characters
of Fe–S, N–O, and Fe–N bonds among the direduced-form
Roussin’s red ester (RRE) [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>]<sup>2–</sup>(<b>1</b>) with
{FeÂ(NO)<sub>2</sub>}<sup>10</sup>-{FeÂ(NO)<sub>2</sub>}<sup>10</sup> core, the reduced-form RRE [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>]<sup>−</sup>(<b>3</b>) with {FeÂ(NO)<sub>2</sub>}<sup>9</sup>-{FeÂ(NO)<sub>2</sub>}<sup>10</sup> core, and
RRE [Fe<sub>2</sub>(μ-SPh)<sub>2</sub>(NO)<sub>4</sub>] (<b>4</b>) with {FeÂ(NO)<sub>2</sub>}<sup>9</sup>-{FeÂ(NO)<sub>2</sub>}<sup>9</sup> core. The major contributions of highest occupied molecular
orbital (HOMO) 113α/β in complex <b>1</b> is related
to the antibonding character between FeÂ(d) and FeÂ(d), FeÂ(d), and S
atoms, and bonding character between FeÂ(d) and NOÂ(Ï€*). The effective
nuclear charge (<i><i>Z</i></i><sub>eff</sub>)
of Fe site can be increased by removing electrons from HOMO to shorten
the distances of Fe···Fe and Fe–S from <b>1</b> to <b>3</b> to <b>4</b> or, in contrast, to
increase the Fe–N bond lengths from <b>1</b> to <b>3</b> to <b>4</b>. The higher IR ν<sub>NO</sub> stretching
frequencies (1761, 1720 cm<sup>–1</sup> (<b>4</b>), 1680,
1665 cm<sup>–1</sup> (<b>3</b>), and 1646, 1611, 1603
cm<sup>–1</sup> (<b>1</b>)) associated with the higher
transition energy of N<sub>1s</sub> →σ*Â(NO) (412.6 eV
(<b>4</b>), 412.3 eV (<b>3</b>), and 412.2 eV (<b>1</b>)) and the higher <i><i>Z</i></i><sub>eff</sub> of Fe derived from the transition energy of Fe<sub>1s</sub> →
Fe<sub>3d</sub> (7113.8 eV (<b>4</b>), 7113.5 eV (<b>3</b>), and 7113.3 eV (<b>1</b>)) indicate that the N–O bond
distances of these complexes are in the order of <b>1 > 3 >
4</b>. The N/S/Fe K-edge XAS spectra as well as DFT computations
reveal the reduction of complex <b>4</b> yielding complex <b>3</b> occurs at Fe, S, and NO; in contrast, reduction mainly occurs
at Fe site from complex <b>3</b> to complex <b>1</b>
Ambient Stable Trigonal Bipyramidal Copper(III) Complexes Equipped with an Exchangeable Axial Ligand
A stable trigonal bipyramidal copperÂ(III)
complex, [PPN]Â[CuÂ(<sup>TMS</sup>PS3)ÂCl] (<b>1</b>, wherein PPN
represents bisÂ(triphenylphosphine)Âiminium), was synthesized from CuCl<sub>2</sub>/PPNCl via intramolecular copperÂ(II) disproportionation. Under
ambient conditions, the axial chloride of <b>1</b> is exchangeable
in solution thus making <b>1</b> serve as an intermediate to
prepare trigonal bipyramidal copperÂ(III) derivatives, e.g., [PPN]Â[CuÂ(<sup>TMS</sup>PS3)Â(N<sub>3</sub>)] (<b>2</b>) and [CuÂ(<sup>TMS</sup>PS3)Â(DABCO)] (<b>3</b>). Diamagnetic complexes <b>1</b>–<b>3</b> were fully characterized by X-ray crystallography,
NMR, UV–vis, and Cu K-edge absorption spectroscopy. A series
of UV–vis titrations were performed to investigate the relative
ligand affinity toward the [CuÂ(<sup>TMS</sup>PS3)] moiety, verifying
the 1:1 binding equilibrium between various ligands. Compared to known
copperÂ(III) compounds, Cu K-edge absorptions of <b>1</b>–<b>3</b> possess lower pre-edge energy and higher shakedown transition
energy, which, respectively, attribute to the electron donation from <sup>TMS</sup>PS3<sup>3–</sup> ligand and their trigonal ligand
field
Water-Soluble Dinitrosyl Iron Complex (DNIC): a Nitric Oxide Vehicle Triggering Cancer Cell Death via Apoptosis
Nitric
oxide (NO) is an important cellular signaling molecule that modulates
various physiological activities. Angiogenesis-promoting activities
of NO-donor drugs have been explored in both experimental and clinical
studies. In this study, a structurally well characterized and water-soluble
neutral {FeÂ(NO)<sub>2</sub>}<sup>9</sup> DNIC [(SÂ(CH<sub>2</sub>)<sub>2</sub>OH)Â(SÂ(CH<sub>2</sub>)<sub>2</sub>NH<sub>3</sub>)ÂFeÂ(NO)<sub>2</sub>] (DNIC <b>2</b>) was synthesized to serve as a NO-donor
species. The antitumor activity of DNIC <b>2</b> was determined
by MTT assay, confocal imaging, and Annexin-V/PI staining. The IC<sub>50</sub> values of DNIC <b>2</b> were 18.8, 42.9, and 38.6
μM for PC-3, SKBR-3, and CRL5866 tumor cells, respectively.
Moreover, DNIC <b>2</b> promoted apoptotic cell death via activation
of apoptosis-associated proteins and inhibition of survival associated
proteins. In particular, DNIC <b>2</b> treatment suppressed
PC-3 tumor growth by 2.34- and 19.3-fold at 7 and 21 days, in comparison
with the control group. These results indicate that water-soluble
DNIC <b>2</b> may serve as a promising drug for cancer therapy