4 research outputs found

    Insight into the Reactivity and Electronic Structure of Dinuclear Dinitrosyl Iron Complexes

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    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 {Fe­(NO)<sub>2</sub>}<sup>10</sup>-{Fe­(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 {Fe­(NO)<sub>2</sub>}<sup>9</sup>-{Fe­(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 {Fe­(NO)<sub>2</sub>}<sup>9</sup>-{Fe­(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 Fe­(d) and Fe­(d), Fe­(d), and S atoms, and bonding character between Fe­(d) and NO­(π*). 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*­(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

    No full text
    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 {Fe­(NO)<sub>2</sub>}<sup>10</sup>-{Fe­(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 {Fe­(NO)<sub>2</sub>}<sup>9</sup>-{Fe­(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 {Fe­(NO)<sub>2</sub>}<sup>9</sup>-{Fe­(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 Fe­(d) and Fe­(d), Fe­(d), and S atoms, and bonding character between Fe­(d) and NO­(π*). 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*­(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

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    A stable trigonal bipyramidal copper­(III) complex, [PPN]­[Cu­(<sup>TMS</sup>PS3)­Cl] (<b>1</b>, wherein PPN represents bis­(triphenylphosphine)­iminium), was synthesized from CuCl<sub>2</sub>/PPNCl via intramolecular copper­(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 copper­(III) derivatives, e.g., [PPN]­[Cu­(<sup>TMS</sup>PS3)­(N<sub>3</sub>)] (<b>2</b>) and [Cu­(<sup>TMS</sup>PS3)­(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 [Cu­(<sup>TMS</sup>PS3)] moiety, verifying the 1:1 binding equilibrium between various ligands. Compared to known copper­(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

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    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 {Fe­(NO)<sub>2</sub>}<sup>9</sup> DNIC [(S­(CH<sub>2</sub>)<sub>2</sub>OH)­(S­(CH<sub>2</sub>)<sub>2</sub>NH<sub>3</sub>)­Fe­(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
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