Photoelectron spectroscopy of HNO− and DNO−

Ellis, H.; Ellison, G. Barney

doi:10.1063/1.444702

Cited by 74 publications

(26 citation statements)

References 53 publications

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lowest triplet ( 3 AЈЈ) excited state of HNO has been determined spectroscopically to lie 18 kcal͞mol above the singlet ( 1 AЈ) ground state (24). QCISD(T) and MP2 calculations reported by Brauman et al (25,26) agree well (Table 1).…”

supporting

confidence: 70%

On the acidity and reactivity of HNO in aqueous solution and biological systems

Bartberger

Fukuto

Houk

2001

Proc. Natl. Acad. Sci. U.S.A.

162

163

View full text Add to dashboard Cite

The gas phase and aqueous thermochemistry and reactivity of nitroxyl (nitrosyl hydride, HNO) were elucidated with multiconfigurational self-consistent field and hybrid density functional theory calculations and continuum solvation methods. The pK a of HNO is predicted to be 7.2 ؎ 1.0, considerably different from the value of 4.7 reported from pulse radiolysis experiments. The ground-state triplet nature of NO ؊ affects the rates of acid-base chemistry of the HNO͞NO ؊ couple. HNO is highly reactive toward dimerization and addition of soft nucleophiles but is predicted to undergo negligible hydration (Keq ‫؍‬ 6.9 ؋ 10 ؊5 ). HNO is predicted to exist as a discrete species in solution and is a viable participant in the chemical biology of nitric oxide and derivatives.T he discoveries of nitric oxide (NO) biosynthesis in mammalian cells and the diverse biological activity associated with NO and NO-derived species (1) have brought intense interest in the physiological chemistry of nitrogen oxides. The chemistry of NO and its biologically accessible oxidized congeners nitrogen dioxide (NO 2 ), nitrite (NO 2 Ϫ ), peroxynitrite (ONOO Ϫ ), dinitrogen trioxide (N 2 O 3 ), and nitrate (NO 3 Ϫ ) is fairly well established (2). By contrast, the reduced congeners such as nitroxyl (HNO) and its conjugate base (NO Ϫ ) are less well understood, and consequently their role in biology is not clear. The importance of HNO or NO Ϫ in biology has often been neglected or dismissed, in part because NO metabolism is thought to be primarily oxidative in nature (3), and because HNO is thought to be only metastable (3), a strong acid (4), and to dimerize readily (5). NO Ϫ is known to react rapidly and irreversibly with NO (6), making the examination of NO Ϫ in the presence of NO difficult. Additionally, HNO might be expected to be electrophilic, and hydration under physiological conditions would serve to attenuate its aqueous reactivity.Nitroxyl (HNO), or its conjugate base, NO Ϫ , is known to be formed under physiological conditions; for example, oxidation of N-hydroxy-L-arginine (an intermediate in NO biosynthesis) (7), reaction of S-nitrosothiols with thiols (8, 9), nitric oxide synthase (10-12), and even direct reduction of NO by mitochondrial cytochrome c (13), may all generate HNO. Nitroxyl has been generated via the interaction of NO with manganese superoxide dismutase (14) and with ubiquinol (15). HNO has biological activity; it can act as a potent cytotoxic agent that causes double-stranded breaks in DNA, depletion of cellular glutathione (16), as well as elicitation of smooth muscle relaxation (17). HNO has been found to be a potent inhibitor of thiol-containing enzymes (18,19) and attenuates the activity of the NMDA receptor via thiol modification, thus providing neuroprotection (20).Much of the fundamental biological chemistry associated with HNO is unknown, aside from the rate constant for dimerization is a typical nucleophile, yet several studies find that HNO generated at physiological pH reacts readily as an electrophile, par...

show abstract

supporting

confidence: 70%

On the acidity and reactivity of HNO in aqueous solution and biological systems

Bartberger

Fukuto

Houk

2001

Proc. Natl. Acad. Sci. U.S.A.

162

163

View full text Add to dashboard Cite

show abstract

“…Furthermore, neither experiment had a reliable method to establish the vibrational temperature of the ions. Nimlos et al did not cool the ions after production from a discharge and with this source have observed vibrational hot bands in other systems, 43 including an estimated vibrational temperature of 1000 K for Si 2 − . 44 Although Hunsicker et al cooled their ions with a supersonic gas expansion, they have measured a vibrational temperature of ∼580 K for P 2 − with the same ion source, 45 so hot bands may also be present in their S 3 − experiment.…”

Section: ■ Discussionmentioning

confidence: 99%

Slow photoelectron velocity-map imaging spectroscopy of cold negative ions

Hock

Kim

Weichman

et al. 2012

The Journal of Chemical Physics

120

139

View full text Add to dashboard Cite

We report high-resolution anion photoelectron spectra of thiozonide (S 3 − ) acquired by slow electron velocity-map imaging (SEVI). The ions were cryogenically cooled within an ion trap before photodetachment. We measure an electron affinity of 2.3630(9) eV, resolving discrepancies in previously reported photoelectron spectra that resulted from the presence of vibrational hot bands. The SEVI spectrum shows well-resolved, extended vibrational progressions in the symmetric stretch and bending modes of S 3 , yielding accurate frequencies for both. ■ INTRODUCTIONWith the possible exception of carbon, sulfur has more complex allotropy than any other element. 1 In addition to the numerous cyclic and polymeric forms in the solid and liquid phases, sulfur vapor is composed of the species S n (2 ≤ n ≤ 8), with trace amounts of S 9 and S 10 . 2 Aside from the diatomic S 2 , S 3 has received the most attention of these species. Its relatively small size makes it accessible to experiment and theory, and additional interest comes about because S 3 is isovalent with ozone. It has been studied by rare gas matrix IR and UV−vis spectroscopy, 3,4 resonance Raman in the gas phase, 5,6 microwave spectroscopy, 7,8 photoionization, 9 and gas-phase absorption. 10 Ab initio calculations on S 3 have focused on the question of whether the cyclic D 3h or the bent C 2v structure is the lowestenergy isomer, 11−14 finding overall agreement with experiment that the C 2v form is the stable form. High-level calculations on the structure, vibrations, and excited states of S 3 have recently been reported by Francisco et al. 15,16 In contrast to neutral S 3 , work on the S 3 − anion has largely been limited to spectroscopy in condensed phases, where it has been studied by electron paramagnetic resonance (EPR), Raman, and absorption spectroscopy. 17−19 As it is the chromophore in ultramarine pigment, 20 many of these investigations were focused on determining the properties of S 3 − in a perturbative mineral matrix or in solution. In addition, electronic absorption spectra have been measured in a cryogenic rare gas matrix. 21 Recently, the anion has been identified as the dominant form of sulfur in certain highpressure and temperature conditions approximating crustal and subduction-zone geologic fluids. 22 The new findings suggest that S 3 − may play an important role in the transport of sulfur and chalcophile metals in the earth.The neutral ← anion transition has been studied by anion photoelectron spectroscopy (PES) with resolution sufficient to resolve a progression of the ν 1 symmetric stretch. 23−25 However, the two previous studies disagreed over which peak in this progression was the vibrational origin. By assuming the anions were at the ground vibrational state, Nimlos et al. 23 obtained an electron affinity (EA) of 2.106(23) eV. Hunsicker et al. 24 found a different onset for the band, suggesting the possibility that the two experiments produced anions with different vibrational temperatures and that some of the low binding en...

show abstract

“…3 [32]. The gas-phase energy gaps are 75 kJ/mol between 3 HNO and 1 HNO [33], and 68 kJ/mol between 1 NO À and 3 NO À [34]. The spin state barrier slows the proton exchange considerably such that the triplet state anion, if generated directly, would have a lifetime of seconds in pH 7 buffer.…”

Section: Hno Revisitedmentioning

confidence: 98%