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

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.