The interaction of negative charge with carbon dioxide – insight into solvation, speciation and reductive activation from cluster studies

Abstract

The interaction of CO 2 with negative charge is of high importance in many natural and industrial processes, since reductive activation is one of the most common and convenient ways to chemically unlock this robust molecule. While free CO 2 does not form stable anions, the accessibility of low-lying molecular orbitals is critical for its chemical versatility and allows CO 2 to act as solvent as well as a reaction partner for negative ions. Experiments on mass selected cluster ions are highly suitable for the study of the fundamental properties of CO 2 and its interaction with excess electrons and anions, since they circumvent many problems associated with experiments in the condensed phase. The combination of mass spectrometry, laser spectroscopy and quantum chemical calculations results in a powerful tool set to address questions of reactivity, ion speciation and solvation, and they can provide key information to understanding the ion chemistry of CO 2 .

Photodissociation of Sodium Iodide Clusters Doped with Small Hydrocarbons

“…The carbond ioxide radicala sw ell as (CO 2 ) n C À clusters have been already observed in spectroscopy experiments [32,[61][62][63][64][65][66][67][68][69][70] and can be stored in the ICR cell on the timescale of seconds.…”

“…The fragment series [Na x I xÀ2 O]C + is not observed at low pulse numbers, which clearly indicates that thesea re formed in secondary reactions. We expect that these arise as secondary products from the [Na x I xÀ2 COO]C + fragments, through elimination of CO as observedi ng as-phase studies of CO 2 C À [64,71] [reaction (9)] or via a charget ransfer transition from CO 2 C À to Na + [reaction (10)]. The photochemistry of pyruvate embedded in the clusterd iffers from the photolysis of pyruvic acid, [44][45][46] partly because the acid proton is not available for rearrangements.…”

Electron‐Induced Reactions in 3‐Bromopyruvic Acid

“…CH 2 CO À is generated through two resonances,t he p 2 * resonance located at 2.6 eV,a nd ac ore-excited resonance peakinga t4 .4 eV.T his anion forms by simple bond cleavage,d uring which the CH 2 group remains at the carbonyl group. [24] In addition to several other fragment anions, OH À ,O À and HCOO À were also reported to form in DEA to pyruvic acid, whereas COO À and CH 2 CO À exclusively formed for the brominated compound. Because the calculationsi ndicateh ydrogenbond formationb etween the hydrogen of the carboxyl group and the a-carbonyl group, OH À may involveo xygen from the carboxyl or carbonyl groups.S everal DEA studies on organic acids [21] and amino acids [22] containing the carboxyl group have been reported already.I nt hese studies, the formation of OH À , O À andH COO À was commonly reported, whereas, to the best of our knowledge,t he COO À anion was reported to form only in very low abundancesr elative to the dehydrogenated parent anion or HCOO À .…”

Reductive Activation of Small Molecules by Anionic Coinage Metal Atoms and Clusters in the Gas Phase

“…[38,39] Although as ingle CO 2 molecule cannot form an anionic state due to its negative EA value (À0.60 eV), [40,41] severals tudies have revealedt hat the coordination to metal atoms makes CO 2 anionss table. [42,43] Ab enchmark study was conducted by Weber et al on AuCO 2 À using IR photodissociation spectroscopy,w hich demonstrated the formation of am etallo-formate anion [Au-CO 2 ] À (Figure 5a, isomer 2). [44] The O=C=Of ramework was appreciablyb ent, indicatingapartial electron transfer from the Au anion to the CO 2 moiety (Scheme 1b).…”