Isomer-specific cryogenic ion vibrational spectroscopy of the D2 tagged Cs+(HNO3)(H2O)n=0–2 complexes: ion-driven enhancement of the acidic H-bond to water

Mitra, Sayoni; Duong, Chinh H.; McCaslin, Laura; Gerber, R. Benny; Johnson, Mark A.

doi:10.1039/c9cp06689f

Cited by 9 publications

(18 citation statements)

References 40 publications

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“…Activation of the IR-forbidden diatomic stretching transitions is attributable to polarization of, and charge transfer to, the diatomic tag by the molecular ion. This behavior and the expected relationship between transition strength and red shift (transition strength and red shift increase together) has been treated in previous work and agrees with the trends observed here. − Red shifts of the H 2 stretching transitions observed in this work are summarized in Figures S5 and S6.…”

Section: Results and Discussionsupporting

confidence: 91%

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

et al. 2021

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Ni II cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) is an efficient catalyst for the selective reduction of CO 2 to CO. A crucial elementary step in the proposed catalytic cycle is the coordination of CO 2 to a Ni I cyclam intermediate. Isolation and spectroscopic characterization of this labile Ni I species without solvent has proven to be challenging, however, and only partial IR spectra have previously been reported using multiple photon fragmentation of ions generated by gas-phase electron transfer to the Ni II cyclam dication at 300 K. Here, we report a chemical reduction method that efficiently prepares Ni I cyclam in solution. This enables the Ni I complex to be transferred into a cryogenic photofragmentation mass spectrometer using inert-gasmediated electrospray ionization. The vibrational spectra of the 30 K ion using both H 2 and N 2 messenger tagging over the range 800−4000 cm −1 were then measured. The resulting spectra were analyzed with the aid of electronic structure calculations, which show strong method dependence in predicted band positions and small molecule activation. The conformational changes of the cyclam ligand induced by binding of the open shell Ni I cation were compared with those caused by the spherical, closed-shell Li I cation, which has a similar ionic radius. We also report the vibrational spectrum of a Ni I cyclam complex with a strongly bound O 2 ligand. The cyclam ligand supporting this species exhibits a large conformational change compared to the complexes with weakly bound N 2 and H 2 , which is likely due to significant charge transfer from Ni to the coordinated O 2 .

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Section: Results and Discussionsupporting

confidence: 91%

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

et al. 2021

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“…This study extends an earlier report 25 that quantified the intramolecular distortions suffered by the HNO 3 molecule in the Cs + •(HNO 3 )(H 2 O) n=0−2 series. That study found that the 450 cm −1 red shift in the acidic OH stretch fundamental of the bare nitric acid HNO 3 ( bare ν OH a in Figure 1A) upon formation of the neutral HNO 3 (H 2 O) van der Waals complex 26 is further displaced by 459 cm −1 when the Cs + cation binds to the acid's −NO 2 group to form the ternary Cs + •(HNO 3 )H 2 O cationic cluster.…”

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confidence: 88%

“…The oscillator strength derived from the water-bound OH group of the acid (hereafter denoted OH a ), appears as a very intense envelope (ν OH a–w in Figure B) with a progression in soft mode combination bands (blue in Figure B above the OH stretching fundamental at 2641 cm –1 ). In that paper, it was noted that the addition of a second water molecule retains this ternary sandwich structure as the second water adopts a position in the first hydration shell of the Cs + ion. Here we follow the structural evolution of the acid during sequential hydration in the series Cs + ·HNO 3 (H 2 O) n =3–11 , which explores the size range through completion of the first hydration shell around Cs + .…”

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Size-Dependent Onset of Nitric Acid Dissociation in Cs⁺·(HNO₃)(H₂O)_n=0–11 Clusters at 20 K

Mitra

Yang

McCaslin

et al. 2021

J. Phys. Chem. Lett.

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We report the water-mediated charge separation of nitric acid upon incorporation into size-selected Cs + •(HNO 3 )(H 2 O) n=0−11 clusters at 20 K. Dramatic spectral changes are observed in the n = 7−9 range that are traced to the formation of many isomeric structures associated with intermediate transfer of the acidic proton to the water network. This transfer is complete by n = 10, which exhibits much simpler vibrational band patterns consistent with those expected for a tricoordinated hydronium ion (the Eigen motif) along with the NO stretching bands predicted for a hydrated NO 3 − anion that is directly complexed to the Cs + cation. Theoretical analysis of the n = 10 spectrum indicates that the dissociated ions adopt a solvent-separated ion-pair configuration such that the Cs + and H 3 O + cations flank the NO 3 − anion in a microhydrated salt bridge. This charge separation motif is evidently assisted by the electrostatic stabilization of the product NO 3 − /H 3 O + ion pair by the proximal metal ion.

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“…However, correlating measured detachment energies with a particular ion pair motif, specifically, when multiple isomers are present, is challenging. More detailed structural information can be extracted using infrared photodissociation (IRPD) spectroscopy, in particular, when performed isomer‐specifically [12] . So far, IRPD studies on microhydrated cluster ions have mainly focused on the characterization of CIPs [13] .…”

Section: Figurementioning

confidence: 99%

Isomer‐Specific Vibrational Spectroscopy of Microhydrated Lithium Dichloride Anions: Spectral Fingerprint of Solvent‐Shared Ion Pairs

2021

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The vibrational spectroscopy of lithium dichloride anions microhydrated with one to three water molecules, [LiCl2(H2O)1–3]−, is studied in the OH stretching region (3800–2800 cm−1) using isomer‐specific IR/IR double‐resonance population labelling experiments. The spectroscopic fingerprints of individual isomers can only be unambiguously assigned after anharmonic effects are considered, but then yield molecular level insight into the onset of salt dissolution in these gas phase model systems. Based on the extent of the observed frequency shifts ΔνOH of the hydrogen‐bonded OH stretching oscillators solvent‐shared ion pair motifs (<3200 cm−1) can be distinguished from intact‐core structures (>3200 cm−1). The characteristic fingerprint of a water molecule trapped directly in‐between two ions of opposite charge provides an alternative route to evaluate the extent of ion pairing in aqueous electrolyte solutions.

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Isomer-specific cryogenic ion vibrational spectroscopy of the D₂ tagged Cs⁺(HNO₃)(H₂O)_n=0–2 complexes: ion-driven enhancement of the acidic H-bond to water

Abstract: Enhancement of the acid–base interaction between HNO3 and water by a proximal Cs+ cation with cryogenic ion vibrational spectroscopy.

Cited by 9 publications

References 40 publications

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Size-Dependent Onset of Nitric Acid Dissociation in Cs⁺·(HNO₃)(H₂O)_n=0–11 Clusters at 20 K

Isomer‐Specific Vibrational Spectroscopy of Microhydrated Lithium Dichloride Anions: Spectral Fingerprint of Solvent‐Shared Ion Pairs

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Isomer-specific cryogenic ion vibrational spectroscopy of the D2 tagged Cs+(HNO3)(H2O)n=0–2 complexes: ion-driven enhancement of the acidic H-bond to water

Abstract: Enhancement of the acid–base interaction between HNO3 and water by a proximal Cs+ cation with cryogenic ion vibrational spectroscopy.

Cited by 9 publications

References 40 publications

Chemical Reduction of NiII Cyclam and Characterization of Isolated NiI Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Chemical Reduction of NiII Cyclam and Characterization of Isolated NiI Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Size-Dependent Onset of Nitric Acid Dissociation in Cs+·(HNO3)(H2O)n=0–11 Clusters at 20 K

Isomer‐Specific Vibrational Spectroscopy of Microhydrated Lithium Dichloride Anions: Spectral Fingerprint of Solvent‐Shared Ion Pairs

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Isomer-specific cryogenic ion vibrational spectroscopy of the D₂ tagged Cs⁺(HNO₃)(H₂O)_n=0–2 complexes: ion-driven enhancement of the acidic H-bond to water

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Chemical Reduction of Ni^II Cyclam and Characterization of Isolated Ni^I Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry

Size-Dependent Onset of Nitric Acid Dissociation in Cs⁺·(HNO₃)(H₂O)_n=0–11 Clusters at 20 K