3‐Hydroxypyridinyl‐Substituted‐1,2,4‐Triazoles as New ESIPT Based Fluorescent Dyes: Synthesis and Structure–Fluorescence Properties Correlations

Abstract

This report presents the design, synthesis, and photophysical study of two new series of promising fluorescent trisubstituted triazoles, 3-hydroxypyridinyl substituted-1,2,4-triazoles (PyOHTr) and 2-pyridonyl substituted-1,2,4-triazoles (PyCOTr). An excited state intramolecular proton transfer (ESIPT) fluorescence mechanism is evidenced for PyOHTr molecules by ab initio theoretical calculations. These fluorescent dyes possess unique optical properties such as large Stokes shifts, dual emission, solvatochromism, solid-state emission and, for one of them, a white light emission, rendering them particularly attractive for future applications in both medicinal chemistry and materials science.

Full-color emission of fluorinated benzothiadiazole-based D–A–D fluorophores and their bioimaging applications

“…In general, the absorption and emission peaks of compounds are red-shifted as the Δ E decreases. 8,39 The reason is that the Δ E is the narrower, the less excitation energy is required for the electron transition. DFT calculations show that compound 3a has the largest Δ E , and the fluorescence data also confirm that 3a has the shortest emission wavelength (Table 1).…”

In silico design of bio-marker detection fluorescent probes

“…In fluorescence dye 4d , we investigated the kinetics of the ESIPT process to determine if the proton transfer, in the excited state, occurs at a similar rate to experimental observations (in the order of ns). 25 We examined the barriers of the IPT by optimizing the transition state (TS) in both the ground and excited states. In each case, we found one imaginary frequency, 1010 i and 1118 i cm −1 , for the ground and excited states, respectively.…”

“…The IPT barrier is expected to result in a de-excitation within approximately 0.04 ns, which is consistent with experimental findings for dual emission in 3-hydroxypyridinyl substituted-1,2,4-triazoles. 25…”

“…42 Looking carefully to the retrosynthetic analysis of the target molecule, substitution at the position 1 and 2 of the acridine core to install respectively the triazole moiety and the hydroxyl group could be done using the synthetic strategy previously set up by the organic chemist co-author. 25…”

“…Some of us have recently reported the synthesis of 3-hydroxypyridyl-1,2,4-triazoles with interesting fluorescent properties such as large Stokes shift and dual emission. 23–25 Throughout our research, we computationally engineer the Stokes shift and emission wavelength of a set of molecules derived from 2-hydroxyphenyl-1,2,4-triazole (referred to as 1 in Fig. 1).…”