Computational Insights into Excited‐State Proton‐Transfer Reactions in Azo and Azomethine Dyes

Abstract

State of the art density functional theory approaches are employed to provide an accurate description of the photophysical properties of azodyes and Schiff bases displaying intramolecular hydrogen-bonding features. These compounds exist as tautomeric mixtures at the ground state and, in the case of Schiff bases, an excited-state intramolecular proton transfer (ESIPT) occurs upon excitation. The experimentally observed photophysical properties are discussed here in light of the theoretical findings. To rationalize the different experimentally observed radiative behavior of the azo and azomethine structures, a nonradiative decay pathway that is possibly active in such systems is determined. The characterization of this deactivation path, tested for two related compounds exhibiting different fluorescence quantum yields, enables us to disentangle the different and contrasting effects governing the excited-state behavior of these molecular systems.

Tautomerism in azo dyes: Border cases of azo and hydrazo tautomers as possible NMR reference compounds

“…The absorption spectra of the compounds were predicted using the TD-DFT formalism. TD-DFT calculations were carried out at the same functional and basis set, which is in accordance with conclusions about the effect of the basis set size and the reliability of the spectral predictions [28][29][30][31][32].…”

Tautomerism in Azo and Azomethyne Dyes: When and If Theory Meets Experiment

“…Compounds 2 and 3 are the core structures of the major class (>60%) of the industrial azodyes (neutral and their metal complexes). Compounds 4 and 5 exhibit interesting photochemical and thermochemical properties in solution and solid state [20,35]. Their tautomeric behavior in solution is very different.…”

Mechanism of Fluorescence Switching in One ESIPT-Based Al3+ Probe

“…[32][33][34][35][36][37] The pK a values characterizing deprotonation of 1 in water were calculated using…”