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Synthesis, photophysical evaluation, and computational study of 2-methoxy- and 2-morpholino pyridine compounds as highly emissive fluorophores in solution and the solid state


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Title: Synthesis, photophysical evaluation, and computational study of 2-methoxy- and 2-morpholino pyridine compounds as highly emissive fluorophores in solution and the solid state
Authors: Hagimori, Masayori / Nishimura, Yasuhisa / Mizuyama, Naoko / Shigemitsu, Yasuhiro
Issue Date: 10-Jul-2019
Publisher: Elsevier Ltd
Citation: Dyes and Pigments, 171, art.no.107705; 2019
Abstract: Two 2-pyridone tautomeric analogs, methoxypyridine 4 and N-methylpyridone 5, were synthesized, and their spectroscopic properties were investigated both experimentally and computationally. A detailed photophysical study reveals that 4 shows high fluorescence quantum yields not only in chloroform but also in ethanol, and the strong fluorescence in solution might be attributed to the enol form (pyridine) of the 2-pyridone. Furthermore, we designed and synthesized novel 2-substitued pyridines to achieve more intense emissions in both solution and the solid state. Substituent modification with phenylsulfonyl,morpholino, and 4-diethylamino groups greatly affected the fluorescence properties, and methoxypyridine 7 and morpholinopyridine compound 8 showed fluorescence in various solvents (Ф = 0.59–0.95) and the solid state (Ф = 0.12–0.15). A hypsochromic shift in the emission maximum wavelength and strong fluorescence in the solid state (Ф = 0.39) were observed for dimorpholinopyridine 9. Morpholinopyridine 11 showed intense fluorescence in all nonpolar and polar solvents. Systematic time-dependent density functional theory calculations were performed for the compounds whose electronic and fluorescent maxima were computationally reproduced with good agreement to those from experiment. In detail, the drastic difference in the emission intensity between 4 and 5 in solution was successfully explained using CASSCF calculations, which revealed the presence of conical intersections between the ground and the excited states.
Keywords: Keto–enol tautomerism of 2-pyridone / Pyridine / Fluorescence / TDDFT / CASSCF / Conical intersection
URI: http://hdl.handle.net/10069/39381
ISSN: 01437208
DOI: 10.1016/j.dyepig.2019.107705
Rights: © 2019 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Type: Journal Article
Text Version: author
Appears in Collections:Articles in academic journal

Citable URI : http://hdl.handle.net/10069/39381

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