5 Gas-phase stabilities of small anions

Kalcher, Josef

doi:10.1039/b101433l

Cited by 2 publications

(2 citation statements)

References 196 publications

(300 reference statements)

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“…Thus, DFT overestimates electron affinity and anion stability. [16] The results obtained for dofetilide are typical of the data obtained for all the compounds modelled. Therefore, of this compound set, only the dofetilide results are reported here; details of the other compounds are given in the Supporting Information.…”

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confidence: 59%

Can computational chemistry be used to predict CID fragmentation of anions?

Wright

Alex²,

Pullen

2015

Rapid Commun. Mass Spectrom.

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Dear Editor,Can computational chemistry be used to predict CID fragmentation of anions?In a research paper published in this journal in 2014, [1] the authors described the use of semi-empirical (AM1; Austin Model 1) quantum chemistry calculations to determine protonation-induced bond length increases in order to predict the cleavage of polarised bonds during CID (collision-induced dissociation) of cations. If the conformational changes due to protonation cause sufficient bond elongation, these bonds are weakened and hence are more likely to cleave. That study used 15 compounds (129 Da to 608 Da molecular weight), involving 102 observed bond cleavages and over 8000 bond length calculations. The success rate was 100% for predicting polarised bond cleavage for these compounds. In addition, over-prediction of bond cleavage was only 34% overall, a significant improvement over the over-prediction of product ion formation by many commercial spectral interpretation software packages. Anions were not considered in the study.Negative ion fragmentation mechanisms have been less studied than those of positive ion. However, similarities have been reported for anion and cation fragmentation which suggest that conformational changes as a result of ionisation may enable prediction of bond cleavage in anions in an analogous manner to that observed for cations. For example, John Bowie of the University of Adelaide, one of the leaders in the field of negative ion mass spectrometry, has identified three mechanisms for the fragmentation of cations formed by deprotonation: [2,3] (1) formation of an ion-molecule complex which dissociates via loss of a neutral molecule; (2) homolytic cleavage forming radicals; (3) rearrangements. These are all mechanisms also reported for positive ion fragmentation, although homolytic cleavage is less common for CID of protonated molecules which favour heterolytic cleavage.Other similarities of even-electron anion CID fragmentation to that of cations include:

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confidence: 59%

Can computational chemistry be used to predict CID fragmentation of anions?

Wright

Alex²,

Pullen

2015

Rapid Commun. Mass Spectrom.

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“…The normal expectation is that only those diatomics with high-spin ground states, where the nuclear charge is strongly unscreened, 12,13 are promising candidates for high electron affinities and excited negative ion states. Previous theoretical investigations on CNa and SiNa 14,15 showed that these molecules are highly polar and possess 4 S À high-spin ground states. Each of these diatomics supports two stable valence-bound anion states, i.e.…”

Section: Introductionmentioning

confidence: 99%

5 Gas-phase stabilities of small anions

Cited by 2 publications

References 196 publications

Can computational chemistry be used to predict CID fragmentation of anions?

Can computational chemistry be used to predict CID fragmentation of anions?

Trends in ground and excited state electron affinities of group 14, 15, and 16 mixed diatomic anions: a computational study

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