Photo-fragmentation spectroscopy of benzylium and 1-phenylethyl cations

Féraud, Géraldine; Dedonder‐Lardeux, C.; Soorkia, Satchin; Jouvet, Christophe

doi:10.1063/1.4858409

Cited by 14 publications

(25 citation statements)

References 62 publications

(93 reference statements)

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“…28 Moreover, we have chosen the RI-CC2 method because it proved useful in describing the electronic transitions of similar aromatic ions with nitrogen functional groups. 29,30 In all the calculations the starting geometries had Cs symmetry and were constrained to distinguish between π or orbitals and A' or A'' excited states. In the case of the benzenediazonium ion fragment, adiabatic excitation energies were calculated in addition to the vertical excitation values.…”

Section: Methodsmentioning

confidence: 99%

Photodissociation UV–Vis Spectra of Cold Protonated Azobenzene and 4-(Dimethylamino)azobenzene and Their Benzenediazonium Cation Fragment

et al. 2016

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Gas phase photodissociation electronic spectra of protonated azobenzene (ABH(+)) and 4-(dimethylamino)azobenzene (dmaABH(+)) were measured in a cryogenically cooled ion trap at temperatures of a few tens of Kelvin. Experimental results were complemented with electronic structure calculations in the ground state at the MP2/cc-pVDZ level of theory, and in the low lying excited states using the RI-CC2 method. Calculated energies revealed that only the trans isomers of the azonium molecular ions (protonation site on the azo group) will likely exist in the trap at the temperatures achieved in the experiment. The first transition of trans-ABH(+) is π* ← π, and the absorption band in the spectrum appears strongly red-shifted from that of the neutral molecule. The calculations showed that upon excitation the quasi-planar ground state (S0) transforms into a chairlike excited state (S1) by twisting the CNNC dihedral angle about 96°. A 41 cm(-1) active vibrational progression found in the ABH(+) spectrum may be associated with the twisting of the azo bond. Conversely, the electronic spectrum of dmaABH(+) exhibits a steep and unstructured S1 ← S0 absorption corresponding to a less distorted S1 state. The next two quasi-degenerate bands in the ABH(+) spectrum evidence sharper onsets and a charge transfer character. Using a second fragmentation laser and an additional He cooling pulse in the trap, it was possible to measure the UV spectrum of cold benzenediazonium fragments.

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Section: Methodsmentioning

confidence: 99%

Photodissociation UV–Vis Spectra of Cold Protonated Azobenzene and 4-(Dimethylamino)azobenzene and Their Benzenediazonium Cation Fragment

et al. 2016

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“…The single gauche conformer is substantially stabilized with respect to the anti isomer by the additional intramolecular NH + ⋅⋅⋅π (cation–π) interaction between the positively charged ammonium group and the highly polarizable π electrons of the aromatic phenyl ring . For this reason, only the gauche conformer is populated in the gas phase, both in a cold molecular beam and at room temperature, that is, the cation–π interaction completely locks H + PEA in the gauche configuration, in stark contrast to neutral PEA (and o F‐PEA).…”

Section: Introductionmentioning

confidence: 99%

Effects of Aromatic Fluorine Substitution on Protonated Neurotransmitters: The Case of 2‐Phenylethylamine

Schütz

Bouchet

Chiavarino

et al. 2016

Chemistry A European J

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Fluorination of pharmaceutical compounds is a common tool to modulate their physiochemical properties. We determine the effects of site-specific aromatic fluorine substitution on the geometric, energetic, vibrational, and electronic properties of the protonated neurotransmitter 2-phenylethylamine (xF-H(+) PEA, x=ortho, meta, para) by infrared multiphoton photodissociation (IRMPD) in the fingerprint range (600-1750 cm(-1) ) and quantum chemical calculations at the B3LYP-D3/aug-cc-pVTZ level. The IRMPD spectra of all ions are assigned to their folded gauche conformers stabilized by intramolecular NH(+) ⋅⋅⋅π hydrogen bonds (H-bonds) between the protonated amino group and the aromatic ring. H→F substitution reduces the symmetry and allows for additional NH(+) ⋅⋅⋅F interactions in oF-H(+) PEA, leading to three distinct gauche conformers. In comparison to oF-H(+) PEA, the fluorination effects on the energy landscape (energy ordering and isomerization barriers) in pF-H(+) PEA and mF-H(+) PEA with one and two gauche conformers are less pronounced. The strengths of the intramolecular NH(+) ⋅⋅⋅F and NH(+) ⋅⋅⋅π bonds are analyzed by the noncovalent interaction (NCI) method.

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“…[46][47][48][49][50] Recent high-resolution experiments showed that rotational temperatures can reach down to 20-35 K (see Section VII C), while the trap is operated at 4.4 K. The biggest advantage of the 3D Paul trap is its ease of operation and its suitability for extracting ions for subsequent time-of-flight mass analyses. A number of cryogenic Paul traps have been built recently to conduct spectroscopy on cold ions, [71][72][73][74] in particular, Johnson and co-workers have developed it into a powerful cryogenic ion spectroscopy technique via H 2 tagging. [28][29][30] The current ESI Paul trap system at Brown University has been significantly improved over the first design.…”

Section: B the Cryogenic Paul Trapmentioning

confidence: 99%

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

Wang

2015

The Journal of Chemical Physics

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Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.

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Photo-fragmentation spectroscopy of benzylium and 1-phenylethyl cations

Cited by 14 publications

References 62 publications

Photodissociation UV–Vis Spectra of Cold Protonated Azobenzene and 4-(Dimethylamino)azobenzene and Their Benzenediazonium Cation Fragment

Photodissociation UV–Vis Spectra of Cold Protonated Azobenzene and 4-(Dimethylamino)azobenzene and Their Benzenediazonium Cation Fragment

Effects of Aromatic Fluorine Substitution on Protonated Neurotransmitters: The Case of 2‐Phenylethylamine

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

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