Conformer structures of eugenol (1a, 1b, and 2) and guaiacol bare molecules computed at the B3LYP/ level. The position of the two oxygen atoms is indicated in the guaiacol molecule.
Isomer (1–6) structures of the guaiacol dimer computed at the B3LYP/ level.
Two-color mass-resolved excitation spectra (2C-MRES) of guaiacol, guaiacol dimer, guaiacol dimer (dimer ), and guaiacol trimer, recorded at 124, 248, 266, and 372 mass channels. The signal depletion in some of the channels due to the detector saturation in the channels of smaller mass is indicated with dotted lines.
UV-UV hole burning and two-color resonant enhanced multiphoton ionization, R2PI, of guaiacol dimer in the region.
(A) IR-UV double resonance in the OH vibrational region of bare guaiacol (upper trace) and guaiacol dimer (lower trace). In both experiments the ionization laser was tuned to the transition at . (B) Comparison of the experimental IR trace with the calculated IR spectrum at the B3LYP/ level for the structures depicted in Fig. 2 . The experimental peak labeled with an asterisk is likely due to a Fermi resonance. Note that only isomer 6 has a single IR-active vibration, as observed experimentally.
Isomer (1–7) structures of the eugenol dimer computed at the B3LYP/ level.
R2PI spectra of eugenol, eugenol dimer, eugenol trimer, and eugenol dimer recorded at the 164, 328, 492, and 346 mass channels. Assignment of eugenol conformers taken from Ref. 32 .
Comparison of UV-UV hole burning, IR-UV hole burning, and R2PI of the dimer of eugenol with the probe laser at . The bands labeled with an asterisk correspond to a second isomer.
(A) IR-UV double resonance of eugenol and eugenol dimer probed at and at , respectively (cf. absorptions in Fig. 8 ). (B) Comparison of the experimental IR traces of the two eugenol dimer isomers with the computed IR spectrum at the B3LYP/ level for the structures shown in Fig. 6 . The experimental bands labeled with asterisks are likely Fermi resonances. Note that only isomer 6 has a single IR-active vibration, as observed experimentally. The experimental peaks labeled with a “?” might be assignable to either a third isomer or a Fermi resonance (see text).
Binding energies (BEs) and basis set superposition error (BSSE) corrections of the six isomers of the dimers of guaiacol, computed at the B3LYP/ level.
Comparison between the experimental OH stretching vibrational energies (and intensities) and those computed at the B3LYP/ level for guaiacol and guaiacol homodimer. The scaling factor for both vibrations of monomer and dimer was 0.97 and the corrected wave numbers are shown in parentheses.
Binding energies (BEs) and basis set superposition error (BSSE) corrections of the isomers of the dimers of eugenol, calculated at the B3LYP/ level. The relative energy is given in parentheses.
Experimental and calculated at the B3LYP/ level energies of the OH stretching vibration of eugenol and its homodimer. The corrected vibrational energies, with a scaling factor of 0.97, are shown in the appropriate column in parentheses.
Observed energy shifts of homodimer electronic transitions with respect to the bare molecule transitions for a set of molecules close to eugenol and guaiacol.
Comparison between the experimental low-energy vibrational bands and those computed at the B3LYP/ level for the eugenol and guaiacol dimers. The ball and stick drawing of the molecule underneath the table is the calculated vibration of guaiacol (named butterfly vibration).
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