Data Set Title: "Reference data for isolated eugenol"

Data Set Authors:
    Baroncelli, Filippo     University of Bologna   ORCID 0000-0003-4807-6939
    Maris, Assimo           University of Bologna   ORCID 0000-0003-2644-0023

Contact Person: Maris, Assimo  University of Bologna ORCID 0000-0003-2644-0023   assimo.maris@unibo.it

Data Set License: This data set is distributed under Creative Commons Attribution 4.0 International.
To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

Publication Year: 2026

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Abstract

This dataset contains the computational and spectroscopic data supporting the investigation of the rotational spectrum of eugenol (2-methoxy-4-(prop-2-en-1-yl)phenol).
The conformational space is explored using density functional theory (DFT) at the B3LYP-D3(BJ)/6-31G(d) and B3LYP-D3(BJ)/def2-TZVP level of calculations.
Twelve non-equivalent minima are characterized, as well as the interconversion pathways between the hydrogen-bonded forms.
All the computational output files are provided.
The R-mub-type spectra of three hydrogen-bonded species (HB) with either an extended (E) or folded (F) orientation of the allyl frame are assigned in the experimental free-jet absorption Stark-modulated spectrum: HB-E1, HB-F, HB-E2.
For the global minimum (HB-E1), previously reported microwave data (3–18 GHz) are taken into account.
All the input and output fitting files in the Watson's S-reduction and the I-r representation are provided.

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Data Set Contents

The dataset consists of a .zip archive named DATA_EUGENOL.zip with the following structure:

DATA_EUGENOL.zip
|   readme.txt
|
+---DFT
|   eugenol_1D_PES_HB_E_allyl_torsion_C4C10_B3LYP_gd3bj_def2TZVP.log
|   eugenol_1D_PES_HB_ethylene_torsion_C10C11_B3LYP_def2TZVP.log
|   eugenol_1D_PES_HB_ethylene_torsion_C10C11_B3LYP_gd3bj_def2TZVP.log
|   eugenol_2D_PES_HB_C4C10_C10C11_B3LYP_gd3bj_631Gd.log
|   eugenol_E_E1_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_E_E1_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_E_E2_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_E_E2_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_E_F_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_E_F_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_HB_E1_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_HB_E1_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_HB_E2_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_HB_E2_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_HB_F_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_HB_F_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_OO_E1_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_OO_E1_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_OO_E2_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_OO_E2_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_OO_F_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_OO_F_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_Z_E1_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_Z_E1_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_Z_E2_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_Z_E2_freq_B3LYP_gd3bj_def2TZVP.log
|   eugenol_Z_F_freq_B3LYP_gd3bj_def2TZVP.fchk
|   eugenol_Z_F_freq_B3LYP_gd3bj_def2TZVP.log
\---FIT
|   eugenol_HBE1.cat
|   eugenol_HBE1.fit
|   eugenol_HBE1.int
|   eugenol_HBE1.lin
|   eugenol_HBE1.par
|   eugenol_HBE1.var
|   eugenol_HBE2.cat
|   eugenol_HBE2.fit
|   eugenol_HBE2.int
|   eugenol_HBE2.lin
|   eugenol_HBE2.par
|   eugenol_HBE2.var
|   eugenol_HBF.cat
|   eugenol_HBF.fit
|   eugenol_HBF.lin
|   eugenol_HBF.par
|   eugenol_HBF.var
    
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Dataset Documentation

Subfolder "DFT" contains Gaussian 16 outputs for conformational analysis of eugenol.
Files with extension .log are Gaussian output files, files with extension .fchk are formatted checkpoint files:
(i) Relaxed potential energy surface scan outputs characterizing the interconversion pathways for the allyl torsion at the B3LYP-D3(BJ)/def2-TZVP level of calculation
(ii) Relaxed potential energy surface scan outputs characterizing the interconversion pathways for the ethylene torsion at both the B3LYP/def2-TZVP and B3LYP-D3(BJ)/def2-TZVP levels of calculation.
(iii) Relaxed 2D potential-energy scan of the allyl and ethylenw torsions at the B3LYP/6-31G(d) level of calculation
(iv) Harmonic frequency calculations on the optimized geometries for all 12 conformers of eugenol at the B3LYP-D3(BJ)/def2-TZVP level of calculation.

Subfolder "FIT" contains CALPGM fitting and prediction files for assigned conformers of eugenol.
For each conformer label (HBE1, HBF, HB2), the folder provides:
(i)   Input fitting files (.par, .lin)
(ii)  Output fitting files (.fit)
(iii) Input prediction files (.var, .int)
(iv)  Output prediction files, calculated up to 100 GHz at a temperature of 10 K (.cat)

Methodology
Computations were performed with Gaussian 16, available at https://gaussian.com/
Spectroscopic fits and predictions were performed using the CALPGM program suite (SPFIT/SPCAT), available at https://spec.jpl.nasa.gov/
The format the files is described here: https://spec.jpl.nasa.gov/ftp/pub/calpgm/spinv.pdf

File Specifics
All files are plain text (ASCII) except Gaussian formatted checkpoint files (.fchk), which are also text-based and readable with a text editor. 
Gaussian .log and .fchk files can be inspected with common molecular viewers, for example GaussView and Avogadro. 
CALPGM files (.par, .var, .int, .lin, .fit, .cat) are text files and can be opened with any editor.

Notes
The data presented here are intended to reproduce the results reported in the article:
"Conformational landscape and free-jet millimeter-wave spectrum of eugenol: the role of dispersion and relaxation dynamics"
Baroncelli F., Calabrese C., Conti L., Evangelisti L., Melandri S., Maris A.
