Role of Standard Diffuse Functions for Computing Hyperfine Splitting Constants in Radical Anions

Guerra, Maurizio

doi:10.1021/jp990012a

Cited by 26 publications

(45 citation statements)

References 38 publications

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“…(A similar situation was found by Guerra for a series of ionic radicals. 51 ) As a result, we observe the tub-like COT ring, similarly as for neutral COT itself.…”

Section: Resultssupporting

confidence: 71%

Cyclooctatetraene dianion—an artifact?

Dominikowska

Palusiak

2011

J Comput Chem

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Cyclooctatetraene in its dianionic form (COT(2-)) is considered to be partially or fully aromatic due to the fact that, unlike its neutral counterpart, it adopts planar structure with CC bonds equalized. However, some authors report that this dianion is neither planar nor aromatic. Thus, we performed a detailed analysis of the COT(2-) case. The influence of several technical parameters on the result of calculations on COT(2-) was investigated. It appears from our analysis that the use of some specific level of approximation may lead to very misleading results in which the COT ring occurs in its neutral structure, in fact being neither planar nor aromatic. Additionally, our results may suggest that COT(2-) dianion is rather an artificial structure (being the result of specific basis set description) and should not occur in experimental conditions.

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“…(A similar situation was found by Guerra for a series of ionic radicals. 51 ) As a result, we observe the tub-like COT ring, similarly as for neutral COT itself.…”

Section: Resultssupporting

confidence: 71%

Cyclooctatetraene dianion—an artifact?

Dominikowska

Palusiak

2011

J Comput Chem

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“…Bending was shown previously to stabilize the related valence anion, HCN Ϫ . 42 The B3LYP/6-31G adiabatic electron affinity ͑AEA͒ of the monomer was found to be Ϫ2.22 eV. Solvating both the neutral and anion using a polarizable continuum model gave a solution-phase AEA of 0.25 eV.…”

Section: Computational Modeling Of Acetonitrile Valence Anionsmentioning

confidence: 97%

Femtosecond electron ejection in liquid acetonitrile: Evidence for cavity electrons and solvent anions

Xia

Peón

Kohler

2002

The Journal of Chemical Physics

138

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Articles you may be interested inPhotodetachment and electron reactivity in 1-methyl-1-butyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide J. Chem. Phys. 137, 034512 (2012); 10.1063/1.4736569Collisional electron transfer to photoexcited acceptor radical anions Two-photon dissociation and ionization of liquid water studied by femtosecond transient absorption spectroscopyExcess electrons were studied in liquid acetonitrile at room temperature by femtosecond pumpprobe spectroscopy. Using Ϸ200 fs, 265 nm laser pulses, electrons were ejected into the liquid by photodetachment from iodide ions and, in separate experiments, by photoionization of indole. A strong and broad absorption band with a maximum near 1400 nm was observed in both systems. A second absorption band was observed at wavelengths below 620 nm for iodide solutions, but was not seen in photoexcited indole due to overlapping excited state absorption. The bands are in good agreement with ones seen previously in nanosecond pulse radiolysis experiments ͓I. P. Bell, M. A. J. Rodgers, and H. D. Burrows, J. Chem. Soc., Faraday Trans. 1 73, 315 ͑1977͔͒. Bell, Rodgers, and Burrows assigned the visible and IR bands to absorption by acetonitrile dimer and monomer anions, respectively. Our results strongly question this interpretation. Instead, we assign the short-wavelength absorption band to a solvent-bound valence anion consisting of one or two acetonitrile molecules and the IR band to a solvated or cavity electron. Low-level quantum chemical calculations indicate that valence anion formation is strongly correlated with CCN bending, but do not provide a clear indication of whether a monomer or dimer valence anion is favored. The highly mobile cavity electron is scavenged by added chloroform at a bimolecular reaction rate of (1.02 Ϯ0.03)ϫ10 11 M Ϫ1 s Ϫ1 . The appearance of both absorption bands within our time resolution suggests that the two forms of the excess electron are produced by prompt reaction with the iodide charge-transfer-to-solvent ͑CTTS͒ excited state. In support of this mechanism, strong static scavenging by chloroform was observed at both visible and IR wavelengths. For iodide in acetonitrile, the signal in the IR decays biexponentially due to competition between geminate recombination of the cavity electron with the parent iodine atom and its reaction with the solvent. Geminate recombination between the solvated electron and the parent iodine atom occurs with a characteristic time constant of Ϸ30 ps, while additional solvent anions are formed in a slow reaction with a time constant of Ϸ260 ps. Approximately 30% of the solvated electrons photodetached from iodide undergo geminate recombination. There is no evidence for geminate reaction between the promptly formed solvent anion and iodine, suggesting that these species are formed at larger initial separation than the IR-absorbing cavity electron/iodine atom pair. In indole, geminate recombination occurs on a slower time scale of Ϸ135 ps.

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“…At this level of theory the radical anion was computed to be not only thermodynamically but also kinetically unstable. It was demonstrated by our group [49] that addition of standard diffuse functions, [50] which are expected to slightly improve hfc constants of stable radical anions, could give meaningless results in this case. Unreliable results were also obtained studying linear conjugated dianions.…”

Section: àmentioning

confidence: 99%

Radical Ions from 3,3′′′,3′′′″‐Tris(butylsulfanyl)‐2,2′:5′,2″:5″,2′′′,5′′′,2′′′′:5′′′′,2′′′″‐sexithiophene: An Experimental and Theoretical Study of the p‐ and n‐Doped Oligomer

Alberti

Ballarin²,

Guerra

et al. 2003

ChemPhysChem

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The 3,3''',3'''''-tris(butylsulfanyl)- 2,2':5',2'':5'',2''',5''',2'''':5'''',2'''''-sexithiophene 1 was investigated through spectroscopic (NMR, EPR, UV/Vis-NIR), electrochemical, spectroelectrochemical and theoretical (DFT) studies. The charged species obtained upon its oxidation and reduction were characterised, showing that 1 can exist in at least five different oxidation states, that is, a neutral species, a radical cation, a dication, a radical anion, and a dianion. The long term stability of the radical cation 1+. was evidenced by the 1H NMR study in the presence of small quantities of trifluoroacetic acid (TFA). This approach allowed a comparison of the relative broadening of proton signals of 1, induced by the electron exchange process with traces of radical cation 1+., and the hfc (hyperfine coupling) constants obtained from the EPR study and DFT calculations. In the radical cation, all of the heterocyclic sulphur atoms are not significantly involved in the delocalisation of the unpaired electron, whereas the opposite holds for the radical anion. Time-dependent DFT calculations reproduced well the wavelengths of the optical transitions observed in the spectroelectrochemical experiments for all the five oxidation states and support the formation of the dianion 1(2-).

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Role of Standard Diffuse Functions for Computing Hyperfine Splitting Constants in Radical Anions

Cited by 26 publications

References 38 publications

Cyclooctatetraene dianion—an artifact?

Cyclooctatetraene dianion—an artifact?

Femtosecond electron ejection in liquid acetonitrile: Evidence for cavity electrons and solvent anions

Radical Ions from 3,3′′′,3′′′″‐Tris(butylsulfanyl)‐2,2′:5′,2″:5″,2′′′,5′′′,2′′′′:5′′′′,2′′′″‐sexithiophene: An Experimental and Theoretical Study of the p‐ and n‐Doped Oligomer

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