Donor-Acceptor Fluorophores and Macrocycles Built Upon Wedge-Shaped π-Extended Phenanthroimidazoles.

J Org Chem

Department of Chemistry, Memorial University, Core Science Facility, 45 Arctic Avenue, St. John's, NL A1C 5S7, Canada.

Published: March 2023

A class of wedge-shaped organic π-fluorophores featuring a 6,9-diphenyl-substituted phenanthroimidazole () core was designed, synthesized, and characterized. Among them, a π-extended derivative containing two electron-withdrawing aldehyde groups was found to exhibit versatile solid-state packing properties as well as strong solvatofluorochromism in different organic solvents. Another derivative that was functionalized with two electron-donating 1,4-dithiafulvenyl (DTF) end groups showed versatile redox reactivities and quenched fluorescence. Treatment of this wedge-shaped bis(DTF)- compound with iodine resulted in oxidative coupling reactions, leading to the formation of intriguing macrocyclic products that carry redox-active tetrathiafulvalene vinylogue (TTFV) moieties in their structures. Mixing the bis(DTF)- derivative with fullerene (C or C) in an organic solvent resulted in substantial fluorescence enhancement (turn-on). In this process, fullerene acted as a photosensitizer to generate singlet oxygen, which in turn induced oxidative C = C bond cleavages and converted nonfluorescent bis(DTF)- into highly fluorescent dialdehyde-substituted . Treatment of TTFV- macrocycles with a small amount of fullerene also led to a moderate degree of fluorescence enhancement, but this is not because of photosensitized oxidative cleavage reactions. Instead, competitive photoinduced electron transfer from TTFV to fullerene can be attributed to their fluorescence turn-on behavior.

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http://dx.doi.org/10.1021/acs.joc.2c02511DOI Listing

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