Predictive value of proton affinity. Ionization energy correlations involving oxygenated molecules

Benoit, Frank M.; Harrison, Alex G.

doi:10.1021/ja00454a015

Cited by 146 publications

(59 citation statements)

References 3 publications

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“…The fact that the carbonyl oxygen is more basic than the hydroxyoxygen was noted already in the 1960s [4, 8, 20, 29 -31], and is in accordance with a general trend for similar carbonyl compounds [32,33]. It is also interesting that structure 1 recently was isolated and characterized in the solid state in the form of HC(OH) 2 ϩ AsF 6 Ϫ [9].…”

Section: Potential Energy Surfacessupporting

confidence: 61%

Decomposition of protonated formic acid: One transition state—Two product channels

Sekiguchi

Bakken

Uggerud

2004

J. Am. Soc. Mass Spectrom.

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The unimolecular chemistry of protonated formic acid, [HCOOH]H ϩ , has been investigated by analyzing the fragmentation of metastable ions (MI) during flight in a sector mass spectrometer, and by proton transfer to formic acid in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. High level ab initio calculations have been used to model the relevant parts of the potential energy surface (PES). In addition, ab initio direct dynamics calculations have been conducted, tracing out 60 different reaction trajectories. The only stable isomer in the mass spectrometric experiments is HC(OH) 2 ϩ , which is the precursor to both observed ionic products, HCO ϩ and H 3 O ϩ , via the same saddle point of the potential energy surface. The detailed motion of the dissociating molecule during passage of the post-transition state region of the PES therefore determines which product ion is formed. After passing the TS a transient HC(O)OH 2 ϩ molecule is first formed. High total energy increases the probability that the nascent water molecule will have sufficient speed to escape the HCO ϩ moiety. Otherwise, typically at low energies, the two units recombine, upon which intra-complex proton transfer is very likely. Eventually, this will give the more stable H 3 O ϩ . (J Am Soc Mass Spectrom 2004, 15, 982-988)

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Section: Potential Energy Surfacessupporting

confidence: 61%

Decomposition of protonated formic acid: One transition state—Two product channels

Sekiguchi

Bakken

Uggerud

2004

J. Am. Soc. Mass Spectrom.

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“…G 0 W 0 calculations have been shown to be adequately converged at the tier 4 level, as compared to reference calculations using larger basis sets augmented with Gaussian basis functions and to experimental vertical IPs for a set of small molecules. 32 For TiO 2 38,39 and IPA 40 the GW@PBEh HOMO and LUMO at the tier 4 level are within 0.1 eV of the experimental IP and EA. For catechol, 41 the GW@PBEh HOMO is very close to the adiabatic IP and about 0.4 eV above the vertical IP.…”

Section: Basis Set Convergencementioning

confidence: 64%

Electronic structure of dye-sensitized TiO2clusters from many-body perturbation theory

et al. 2011

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The development of new types of solar cells is driven by the need for clean and sustainable energy. In this respect dye sensitized solar cells (DSC) are considered as a promising route for departing from the traditional solid state cells. The physical insight provided by computational modeling may help develop improved DSCs. To this end it is important to obtain an accurate description of the electronic structure, including the fundamental gaps and level alignment at the dye-TiO 2 interface. This requires a treatment beyond ground-state density functional theory (DFT). We present a many-body perturbation theory study, within the G 0 W 0 approximation, of two of the crystalline phases of dye-sensitized TiO 2 clusters, reported by Benedict and Coppens [J Am Chem Soc 132 (9), 2938 (2010)]. We obtain geometries in good agreement with experiment by using DFT with the Tkatchenko-Scheffler van der Waals correction. We demonstrate that even when DFT gives a good description of the valence spectrum and a qualitatively correct picture of the electronic structure of the dye-TiO 2 interface, G 0 W 0 calculations yield more valuable quantitative information regarding the fundamental gaps and level alignment. In addition, we systematically investigate the issues pertaining to G 0 W 0 calculations, namely: (i) convergence with respect to the number of basis functions, (ii) dependence on the mean field starting point, and (iii) the validity of the assumption that the DFT wave-function is a good approximation to the quasi-particle wave-function. We show how these issues are manifested for dye molecules and for dye-sensitized TiO 2 clusters.

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“…The key feature of the plot, though, is that the compounds are separated into two distinct groups, with the smaller group having GB values much higher than would be anticipated, based upon their high IEs and the clear trend in the main group. The reason for the separation is that the smaller group are substituent-protonating, rather than ring-protonating, and their GB values do not reflect the basicity of the ring, which is low because of the EW substituent effect, but that of the substituent itself [21][22][23]. Significantly, all of the compounds from the substituent-protonating group were observed to selfprotonate during Test 1 of the experiments; the only self-protonating dopant not among the substituentprotonating group of Figure 2 was phenyl acetate, which is absent from the plot altogether.…”

Section: Discussion Of Results For Substituted-benzenesmentioning

confidence: 99%

Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization

Robb

Smith

Blades

2008

J. Am. Soc. Mass Spectrom.

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Atmospheric pressure photoionization (APPI) using a dopant enables both polar and nonpolar compounds to be analyzed by LC/MS. To date, the charge exchange ionization pathway utilized for nonpolar compounds has only been efficient under restrictive conditions, mainly because the usual charge exchange reagent ions-the dopant photoions themselves-tend to be consumed in proton transfer reactions with solvent and/ or dopant neutrals. This research aims to elucidate the factors affecting the reactivities of substituted-benzene dopant ions; another, overriding, objective is to discover new dopants for better implementing charge exchange ionization in reversed-phase LC/MS applications. The desirable properties for a charge exchange dopant include low reactivity of its photoions with solvent and dopant neutrals and high ionization energy (IE). Reactivity tests were performed for diverse substituted-benzene compounds, with substituents ranging from strongly electron withdrawing (EW) to strongly electron donating (ED). The results indicate that both the tendency of a dopant's photoions to be lost through proton transfer reactions and its IE depend on the electron donating/withdrawing properties of its substituent(s): ED groups decrease reactivity and IE, while EW groups increase reactivity and IE. Exceptions to the reactivity trend for dopants with ED groups occur when the substituent is itself acidic. All told, the desirable properties for a charge exchange dopant tend towards mutual exclusivity. Of the singlysubstituted benzenes tested, chloro-and bromobenzene provide the best compromise between low reactivity and high IE. Several fluoroanisoles, with counteracting EW and ED groups, may also provide improved performance relative to the established dopants. . Despite its name, analyte ionization in APPI is mostly due to ion-molecule reactions, following the photoionization of a primary reagent. The primary reagent is usually added purposefully, and is then termed a dopant, though this may not be required if a bulk component of the sample stream itself is photoionizable. Once the primary reagent ions are generated, the ensuing ion-molecule reactions may lead to analyte ionization through either proton transfer or charge exchange (electron transfer), depending upon the properties of the analyte and the chemical environment of the source. In general, polar compounds may be readily Address reprint requests to Michael W. Blades, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, B.C., Canada, V6T 1Zl, Canada. E-mail: blades@chem.ubc.ca ionizable via either ionization pathway, whereas nonpolar compounds are less amenable to proton transfer and may require charge exchange. To date, the charge exchange ionization pathway has only been efficient under restrictive conditions, mainly because of the tendency of the usual dopant ions to react by proton transfer with reversed-phase solvents and/or dopant neutrals. No study of the factors affecting the reactivity of dopant ions with solvent or dopant neu...

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Predictive value of proton affinity. Ionization energy correlations involving oxygenated molecules

Cited by 146 publications

References 3 publications

Decomposition of protonated formic acid: One transition state—Two product channels

Decomposition of protonated formic acid: One transition state—Two product channels

Electronic structure of dye-sensitized TiO2clusters from many-body perturbation theory

Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization

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