Influence of the Intramolecular Hydrogen Bond on the Fluorescence of 2-ortho-Aminophenyl Pyridines


The dynamic nature of excited-state intramolecular proton transfer (ESIPT) and its effect on emission spectra is an attractive strategy to create multi-emissive dyes. Here we describe the behavior of a series of hydrogen-bonded triphenylpyridines with a set of donor-acceptor combinations that allowed us to perceive the influence of each substitution on the photophysical properties of the dyes. The susceptibility of these ESIPT moieties to pH variations was also studied, elucidating that the level of protonation had a significant effect on the emission color. The assignment of each emission band was made by using DFT and td-DFT calculations that were in agreement with the experimental results. This study emphasizes the versatility of triphenylpyridines that can be synthesized effortlessly with a logical and independent C-2, C-4 and C-6 substitution in order to have the desired ESIPT modulation and subsequent multi-emission response.



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Esteves, CIC; Fontes, LFB; Rocha, J; Silva, AMS; Guieu, S

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Thanks are due to the University of Aveiro, FCT/MEC, Centro 2020 and Portugal2020, the COMPETE program, and the European Union (FEDER program) via the financial support to the LAQV-REQUIMTE (UIDB/50006/2020), to the CICECO-Aveiro Institute of Materials (UID/CTM/50011/2019, UIDB/50011/2020 & UIDP/50011/2020), financed by national funds through the FCT/MCTES, to the Portuguese NMR Network, and to the PAGE project Protein aggregation across the lifespan (CENTRO-01-0145-FRDER-000003, CICE research contract). S.G. is supported by national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. LFBF thanks the FCT for his PhD grant (SFRH/BD/150663/2020).

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