We report the electronic absorption spectroscopy of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its fluorinated derivatives (F2TCNQ and F4TCNQ), well-known electron-accepting molecules in common organic solvents (toluene, chlorobenzene, acetonitrile, and ethanol) under controlled exposure to air (O2) and UV light. All compounds (FxTCNQ (x = 0, 2, 4)) were stable in a neutral state (FxTCNQ0) in toluene and chlorobenzene, even under both O2 and UV light. On the other hand, in EtOH, the formation of FxTCNQ·− was monitored upon controlled exposure to O2 or UV light. Especially in air-equilibrated ethanol upon the UV-illumination, efficient α,α-dicyano-p-toluoylcyanide anion (DCTC−) and its fluorinated derivatives were generated evinced by the absorption peak near 480 nm, whereas the reaction was shut off by removing O2 or blocking UV light, thereby keeping FxTCNQ·− stable. However, even in deaerated ethanol, upon the UV-illumination, the anion formation of TCNQ and its fluorinated derivatives (FxTCNQ·−, x = 0, 2, 4) was inevitable, showing the stability of FxTCNQ0 depends on the choice of solvent.
Bibliographical noteFunding Information:
This work was supported by the Ewha Womans University Research Grant of 2021 and National Research Foundation of Korea grant funded by the Korea government (NRF-2020R1F1A1073716).
© 2023, The Author(s).
- Electron acceptor
- Radical anion