Solvatochromism of fluorescence and the excited state of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane

The optical properties of quinodimethanes have attracted considerable interest recently. Here, we report the fluorescence characteristics of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), which is utilized as a versatile electron acceptor and a p-type dopant. A solvatochromic shift of the fluorescence and a decrease in the fluorescence quantum yield were observed as the solvent polarity increased. The fluorescence emissive state of F4TCNQ was assigned to the intramolecular charge-transfer (ICT) state. A heavy atom effect on the fluorescence intensity was observed, indicating the occurrence of intersystem crossing from the ICT state to the triplet state. A hypothetical model of the excited state of F4TCNQ is proposed.

Automated summary

The article reports on the fluorescence characteristics of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), showing a solvatochromic shift and decreased fluorescence quantum yield with increasing solvent polarity. The fluorescence emissive state of F4TCNQ is identified as the intramolecular charge-transfer (ICT) state, with a heavy atom effect observed on the fluorescence intensity, suggesting intersystem crossing to the triplet state.