Infrared spectra of the phenol–Ar and phenol–N2 cations: proton-bound versus π-bound structures

Solcà, Nicola; Dopfer, Otto

doi:10.1016/s0009-2614(00)00675-8

Cited by 93 publications

(167 citation statements)

References 27 publications

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“…As TRA + is expected to form weak H-bonds with nonpolar N 2 molecules, their characteristic features become accessible by direct comparison with the strong conventional H-bond observed in TRA + -H 2 O. The current TRA + -(N 2 ) n study extends our previous characterization of A + -(N 2 ) n clusters with more simple aromatic chromophores (A + ), 32 such as benzene, 33,34 phenols and naphthols, [35][36][37][38][39] anilines, [40][41][42] imidazole, 43 cyclopropenyl, 44,45 and indole (In). 46 These studies revealed that the microsolvation process of acidic aromatic ions in molecular nitrogen is dominated by the competition between two principal binding motifs, namely H-bonding to the acidic functional OH and NH groups and p-stacking to the aromatic ring.…”

Section: Introductionsupporting

confidence: 58%

Weak hydrogen bonding motifs of ethylamino neurotransmitter radical cations in a hydrophobic environment: infrared spectra of tryptamine+–(N2)n clusters (n ≤ 6)

Sakota

Schütz

Schmies

et al. 2014

Phys. Chem. Chem. Phys.

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Size-selected clusters of the tryptamine cation with N 2 ligands, TRA + -(N 2 ) n with n = 1-6, are investigated by infrared photodissociation (IRPD) spectroscopy in the hydride stretch range and quantum chemical calculations at the oB97X-D/cc-pVTZ level to characterize the microsolvation of this prototypical aromatic ethylamino neurotransmitter radical cation in a nonpolar solvent. Two types of structural isomers exhibiting different interaction motifs are identified for the TRA + -N 2 dimer, namely the TRA + -N 2 (H) global minimum, in which N 2 forms a linear hydrogen bond (H-bond) to the indolic NH group, and the less stable TRA + -N 2 (p) local minima, in which N 2 binds to the aromatic p electron system of the indolic pyrrole ring. The IRPD spectrum of TRA + -(N 2 ) 2 is consistent with contributions from two structural H-bound isomers with similar calculated stabilization energies. The first isomer, denoted as TRA + -(N 2 ) 2 (2H), exhibits an asymmetric bifurcated planar H-bonding motif, in which both N 2 ligands are attached to the indolic NH group in the aromatic plane via H-bonding and charge-quadrupole interactions. The second isomer, denoted as TRA + -(N 2 ) 2 (H/p), has a single and nearly linear H-bond of the first N 2 ligand to the indolic NH group, whereas the second ligand is p-bonded to the pyrrole ring. The natural bond orbital analysis of TRA + -(N 2 ) 2 reveals that the total stability of these types of clusters is not only controlled by the local H-bond strengths between the indolic NH group and the N 2 ligands but also by a subtle balance between various contributing intermolecular interactions, including local H-bonds, charge-quadrupole and induction interactions, dispersion, and exchange repulsion. The systematic spectral shifts as a function of cluster size suggest that the larger TRA + -(N 2 ) n clusters with n = 3-6 are composed of the strongly bound TRA + -(N 2 ) 2 (2H) core ion to which further N 2 ligands are weakly attached to either the p electron system or the indolic NH proton by stacking and charge-quadrupole forces.

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Section: Introductionsupporting

confidence: 58%

Weak hydrogen bonding motifs of ethylamino neurotransmitter radical cations in a hydrophobic environment: infrared spectra of tryptamine+–(N2)n clusters (n ≤ 6)

Sakota

Schütz

Schmies

et al. 2014

Phys. Chem. Chem. Phys.

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“…The former can be assigned to n H OH , because its frequency matches with n H OH of ionized PhOH + -Ar. [5][6][7][8] The observation of n H OH indicates the occurrence of p -H isomerization, since the Rydberg states are prepared by Franck-Condon restricted photoexcitation from the p-bound S 1 state. The n H OH frequency observed here (B3490 cm À1 ) is somewhat blue-shifted from that observed for cold PhOH + -Ar clusters generated by collisional aggregation of PhOH + and Ar (n H OH = 3468 cm À1 ).…”

Section: Mati-ir Spectramentioning

confidence: 99%

“…The n H OH frequency observed here (B3490 cm À1 ) is somewhat blue-shifted from that observed for cold PhOH + -Ar clusters generated by collisional aggregation of PhOH + and Ar (n H OH = 3468 cm À1 ). [5][6][7][8] This blue-shift has been interpreted as weakening of the H-bond in hot clusters caused by redistribution of internal energy during the course of the exothermic p -H isomerization reaction (100-300 cm À1 ) 14,15,17,28 among the three intermolecular modes. 8,9 The lowest-frequency vibration of PhOH + has B180 cm À1 31 and is the only intramolecular vibration, which can be excited by the excess energy available in this reaction.…”

Section: Mati-ir Spectramentioning

confidence: 99%

“…The experimental integrated intensity of n H OH is of the same order as that of n p OH , although the IR oscillator strength of n H OH has been estimated to be about two times stronger than that of n p OH . 5,8 From these values, the relative population of the H-bound structure generated by the reaction is then obtained as 0.5 of that of the p-bound population. This limited reaction yield has been interpreted by a reaction model including p -H forward and H -p backward reactions, and the lack of intracluster vibrational energy redistribution (IVR) from the reaction coordinate.…”

Section: Mati-ir Spectramentioning

confidence: 99%

“…This interaction switching was derived from IR spectra of ionized clusters, PhOH + -Rg, generated by aggregation of Rg atoms following ionization of PhOH, which leads predominantly to the formation of the most stable isomer. [5][6][7][8][9][10][11][12][13] The IR spectra show broad red-shifted hydrogen-bonded OH stretching vibrations (n H OH ) of structures in which the Rg atoms bind to the OH group. Recent high level ab initio calculations have also supported this switching in the interaction motif upon ionization.…”

Section: Introductionmentioning

confidence: 99%

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Mass analyzed threshold ionization detected infrared spectroscopy: isomerization activity of the phenol–Ar cluster near the ionization threshold

Miyazaki

Yoshikawa

Michels

et al. 2015

Phys. Chem. Chem. Phys.

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The structure of the phenol-argon cluster (PhOH-Ar) in high-n Rydberg states is investigated by the newly developed technique of mass analyzed threshold ionization detected infrared (MATI-IR) spectroscopy. This method selectively measures IR spectra of molecular clusters in very high-n Rydberg states (n 4 100) utilized in zero kinetic energy (ZEKE) photoelectron and MATI spectroscopy, whose ionic cores are essentially the same as the corresponding bare cation. The MATI-IR spectrum exhibits only the free OH stretching vibration (n p OH ) when the p-bound cluster of the neutral ground electronic state (S 0 ) is resonantly excited via the S 1 origin to Rydberg states converging to its adiabatic ionization energy level, IE 0 (p). When Rydberg states converging to vibrationally excited levels of the local p-bound minimum are prepared, in addition to n p OH also the hydrogen-bonded OH stretching vibration (n H OH ) of the H-bonded global minimum is observed in the MATI-IR spectra, even for vibrational excitation of only 14 cm À1 above IE 0 (p). These results show that the p -H site switching reaction of the Ar ligand from the aromatic ring to the OH group proceeds only from vibrationally excited states in the p-bound cation core with a small barrier of less than 14 cm À1 from IE 0 (p). On the other hand, directly photoionized PhOH + -Ar shows both n H OH and n p OH in the IR spectra, even when it is just ionized to IE 0 (p). This result implies that the ionizationinduced p -H site switching occurs without excess energy in the H-bound or p-bound cations, in contrast to very high-n Rydberg states converging to levels of the p-bound cation. The different efficiencies of the site switching for the Rydberg ion core and the bare ion and the mechanism for the p -H site switching are interpreted by direct ionization from the p-bound to the H-bound structures in addition to the conventional vertical ionization and transitions to high-n Rydberg states.

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General and Theoretical Aspects of Phenols

Nguyen

Kryachko

Vanquickenborne

2009

Patai's Chemistry of Functional Groups

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Introduction Molecular Structure and Bonding of Phenol Structures and Properties of Substituted Phenols Energetics of some Fundamental Processes Hydrogen Bonding Abilities of Phenols Open Theoretical Problems Acknowledgements

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Infrared spectra of the phenol–Ar and phenol–N2 cations: proton-bound versus π-bound structures

Cited by 93 publications

References 27 publications

Weak hydrogen bonding motifs of ethylamino neurotransmitter radical cations in a hydrophobic environment: infrared spectra of tryptamine+–(N2)n clusters (n ≤ 6)

Weak hydrogen bonding motifs of ethylamino neurotransmitter radical cations in a hydrophobic environment: infrared spectra of tryptamine+–(N2)n clusters (n ≤ 6)

Mass analyzed threshold ionization detected infrared spectroscopy: isomerization activity of the phenol–Ar cluster near the ionization threshold

General and Theoretical Aspects of Phenols

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