Influence of the meso-substituent on strongly red emitting phenanthrene-fused boron–dipyrromethene (BODIPY) fluorophores with a propeller-like conformation.
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2018
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Elsevier
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Descalzo, Ana B., et al. «Influence of the Meso -Substituent on Strongly Red Emitting Phenanthrene-Fused Boron–Dipyrromethene (BODIPY) Fluorophores with a Propeller-like Conformation». Journal of Photochemistry and Photobiology A: Chemistry, vol. 352, febrero de 2018, pp. 98-105. https://doi.org/10.1016/j.jphotochem.2017.10.034.
Abstract
Highly emissive phenanthrene-fused boron–dipyrromethene (PBDP) dyes have been spectroscopically characterized in a series of solvents. The influence of different substituents (−H, −I, −CN, −DMA or a 15C5-crown ether) in the para-position of a phenyl ring attached to the meso-position of the BODIPY core is discussed. This family of dyes has an intense emission at λ ≥ 630 nm, with fluorescence quantum yields between 0.7 and 1.0 in all solvents studied, except in the case of the dimethylamino-substituted derivative, PBDP-DMA, which undergoes excited-state intramolecular charge transfer (CT), leading to broadband dual fluorescence in highly polar solvents. Introduction of a weaker electron donor such as a benzocrown to the meso-position is not able to trigger a second (charge or electron transfer) process and, interestingly, heavy atom (iodine, PBDP-I derivative) substitution at that moiety does also not have a relevant influence on the photophysics, i.e., enhanced intersystem crossing was not observed. Electrochemical studies of PBDP-DMA complement the data reported and stress the fact that the decrease in fluorescence of PBDP-DMA in highly polar solvents is due to an excited-state CT process rather than to a photoinduced electron transfer (PET).