IR spectra of resorcinol+–Ar  cluster cations (n= 1, 2): Evidence for photoionization-induced π → H isomerization

Patzer, A. B. C.; Langer, Judith; Knorke, Harald; Neitsch, Helge; Dopfer, Otto; Miyazaki, Mitsuhiko; Hattori, Kaori; Ishiuchi, Shun‐ichi; Fujii, Masaaki

doi:10.1016/j.cplett.2009.04.030

Cited by 17 publications

(32 citation statements)

References 45 publications

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“…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%

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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Section: Introductionmentioning

confidence: 99%

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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“…This charge-induced p -H switch is a general phenomenon for acidic aromatic molecules interacting with nonpolar ligands, 8 and has been established for a variety of aromatic molecules featuring acidic NH and OH proton donor groups. [11][12][13][14][15][16][17][18] The present work investigates the structures of the PhOH-Ar 3 complex in the neutral (S 0 ) and cation (D 0 ) ground electronic states and the dynamics of the p -H switch induced by the ionization process using IR spectroscopy. For this purpose, we briefly summarize the current knowledge of phenol-Ar n clusters, which have been investigated up to n = 3.…”

Section: Introductionmentioning

confidence: 99%

Ionization-induced π → H site switching dynamics in phenol–Ar₃

Ishiuchi

Miyazaki

Sakai

et al. 2011

Phys. Chem. Chem. Phys.

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Electronic excitation spectra of the S(1)← S(0) transition obtained by resonance-enhanced two-photon ionization (REMPI) are analysed for phenol-Ar(n) (PhOH-Ar(n)) clusters with n≤ 4. An additivity rule has been established for the S(1) origin shifts upon sequential complexation at various π binding sites, which has allowed for the identification of two less stable isomers not recognized previously, namely the (2/0) isomer for n = 2 and the (2/1) isomer for n = 3. Infrared (IR) spectra of neutral PhOH-Ar(n) and cationic PhOH(+)-Ar(n) clusters are recorded in the vicinity of the OH and CH stretch fundamentals (ν(OH), ν(CH)) in their S(0) and D(0) ground electronic states using IR ion dip spectroscopy. The small monotonic spectral redshifts Δν(OH) of about -1 cm(-1) per Ar atom observed for neutral PhOH-Ar(n) are consistent with π-bonded ligands. In contrast, the IR spectra of the PhOH(+)-Ar(n) cations generated by resonant photoionization of the neutral precursor display the signature of H-bonded isomers, suggesting that ionization triggers an isomerization reaction, in which one of the π-bonded Ar ligands moves to the more attractive OH site. The dynamics of this isomerization reaction is probed for PhOH(+)-Ar(3) by picosecond time-resolved IR spectroscopy. Ionization of the (3/0) isomer of PhOH(+)-Ar(3)(3π) with three π-bonded Ar ligands on the same side of the aromatic ring induces a π→ H switching reaction toward the PhOH(+)-Ar(3)(H/2π) isomer with a time constant faster than 3 ps. Fast intracluster vibrational energy redistribution prevents any H →π back reaction.

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“…In contrast, the corresponding A + ÀL dimer cations prefer hydrogen bonds to the acidic functional groups due to additional charge-induced interactions arising from the excess charge. This ionization-induced p!H switch in the preferred A (+) ÀL binding motif has recently been established through IR spectroscopy and quantum chemical calculations for a variety of aromatic molecules that interact with rare gas (Rg) atoms, CH 4 , and N 2 , [8] including (substituted) phenols, [20][21][22][23][24][25][26][27][28] naphthol, [29] aniline, [30][31][32] imidazole, [33,34] and indole. [35] In some of these clusters, the ionization-induced p!H switch triggers an intermolecular isomerization reaction upon photoionization, which occurs on the picosecond timescale [36][37][38] and is usually inferred from IR spectra recorded before and after ionization, even when using nanosecond laser systems.…”

Section: Introductionmentioning

confidence: 99%

Microsolvation of the 4‐Aminobenzonitrile Cation (ABN⁺) in a Nonpolar Solvent: IR Spectra of ABN⁺L_n (L=Ar and N₂, n≤4)

et al. 2012

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IR photodissociation (IRPD) spectra of mass-selected cluster ions of 4-aminobenzonitrile (ABN(+)) with up to four Ar and N2 ligands are recorded over the spectral range of the N-H stretching vibrations (ν(s/a)) of ABN(+) in its (2)B1 ground electronic state. ABN(+)-L(n) clusters are produced in an electron impact cluster ion source, which predominantly generates the most stable isomer of a given cluster ion. Vibrational frequency shifts of ν(s/a) provide information about the sequential microsolvation process of ABN(+) in a nonpolar solvent. In ABN(+)-(N2)n, the first two ligands fill a first subshell by forming hydrogen bonds to the acidic protons of the amino group, whereas further ligands bind more weakly to the aromatic ring (π bonds). Although the preferred cluster growth sequence in ABN(+)-Ar(n) is similar, several isomers are observed because the hydrogen bonds are only slightly stronger than the π bonds. Quantum chemical calculations at the M06-2X/aug-cc-pVTZ level confirm the cluster growth sequence derived from the IR spectra and provide further details of the intermolecular potential. The calculated binding energies of D0(H)=532 and 895 cm(-1) for hydrogen-bonded and D0(π)=512 and 530 cm(-1) for π-bonded Ar and N2 ligands are consistent with the observed photofragmentation branching ratios. Comparison between ABN(+)-L(n) and the corresponding clusters with the aniline cation demonstrates that the NH protons of the amino group become slightly more acidic upon H→CN substitution at the para position. Comparison between charged and neutral ABN((+))-L dimers indicates that ionization switches the preferred ion-ligand binding motif from π to hydrogen bonding.

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IR spectra of resorcinol+–Ar cluster cations (n= 1, 2): Evidence for photoionization-induced π → H isomerization

Cited by 17 publications

References 45 publications

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

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

Ionization-induced π → H site switching dynamics in phenol–Ar₃

Microsolvation of the 4‐Aminobenzonitrile Cation (ABN⁺) in a Nonpolar Solvent: IR Spectra of ABN⁺L_n (L=Ar and N₂, n≤4)

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IR spectra of resorcinol+–Ar cluster cations (n= 1, 2): Evidence for photoionization-induced π → H isomerization

Cited by 17 publications

References 45 publications

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

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

Ionization-induced π → H site switching dynamics in phenol–Ar3

Microsolvation of the 4‐Aminobenzonitrile Cation (ABN+) in a Nonpolar Solvent: IR Spectra of ABN+Ln (L=Ar and N2, n≤4)

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Ionization-induced π → H site switching dynamics in phenol–Ar₃

Microsolvation of the 4‐Aminobenzonitrile Cation (ABN⁺) in a Nonpolar Solvent: IR Spectra of ABN⁺L_n (L=Ar and N₂, n≤4)