Conformational and Tautomeric Effects on the excited-states of Sulfonated Azo Dyes
- 1University of Alberta
- 2Universidade Federal de São Carlos
Abstract
In this work, we present a systematic investigation of the ground- and excited-states of six anionic sulfonated azo dyes with broad applications in the textile industry: Allura Red, Amaranth, Carmoisine, Ponceau, Red 2G, and Sunset Yellow. Ground-state properties were evaluated using density functional theory (DFT) at the ωB97X-D4/ma-def2-SVP level of theory. To identify the most suitable functional for excited-state calculations and to assess vertical excitation energies to low-lying excited-states, we tested a series of hybrid, meta-hybrid, and range-separated hybrid functionals from Jacob's ladder using the Tamm-Dancoff approximation (TDA) and the ma-def2-SVP basis set and compared to results from RI-CC2 and STEOM-DLPNO-CCSD approaches. excited-state properties were then further examined using TDA at the CAM-B3LYP//ωB97X-D4/ma-def2-SVP level of theory. Additionally, the quantum theory of atoms in molecules (QTAIM) was applied to explore density-related properties in both ground and excited-states. We found, perhaps not surprisingly, that excitation weakens the \ce{N=N} bond in both the enol and keto forms of the dyes, but with variations depending on the molecule, conformer, and electronic state.
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BibTeX
@misc{mendes2026conformational,
title = {{Conformational and Tautomeric Effects on the excited-states of Sulfonated Azo Dyes}},
author = {Rodrigo Araujo Mendes and Victor A. S. da Mata and Ismael A. Elayan and Alex Brown and Gabriel L. C. de Souza},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv-2025-rfk58/v2},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv-2025-rfk58/v2},
note = {CC BY},
}
RIS
TY - UNPB
TI - Conformational and Tautomeric Effects on the excited-states of Sulfonated Azo Dyes
AU - Rodrigo Araujo Mendes
AU - Victor A. S. da Mata
AU - Ismael A. Elayan
AU - Alex Brown
AU - Gabriel L. C. de Souza
PY - 2026
DA - 2026/10/22
PB - ChemRxiv
DO - 10.26434/chemrxiv-2025-rfk58/v2
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv-2025-rfk58/v2
AB - In this work, we present a systematic investigation of the ground- and excited-states of six anionic sulfonated azo dyes with broad applications in the textile industry: Allura Red, Amaranth, Carmoisine, Ponceau, Red 2G, and Sunset Yellow. Ground-state properties were evaluated using density functional theory (DFT) at the ωB97X-D4/ma-def2-SVP level of theory. To identify the most suitable functional for excited-state calculations and to assess vertical excitation energies to low-lying excited-states, we tested a series of hybrid, meta-hybrid, and range-separated hybrid functionals from Jacob's ladder using the Tamm-Dancoff approximation (TDA) and the ma-def2-SVP basis set and compared to results from RI-CC2 and STEOM-DLPNO-CCSD approaches. excited-state properties were then further examined using TDA at the CAM-B3LYP//ωB97X-D4/ma-def2-SVP level of theory. Additionally, the quantum theory of atoms in molecules (QTAIM) was applied to explore density-related properties in both ground and excited-states. We found, perhaps not surprisingly, that excitation weakens the \ce{N=N} bond in both the enol and keto forms of the dyes, but with variations depending on the molecule, conformer, and electronic state.
ER -