Long-wavelength chromophores are developed based on fluorescein derivatives by introducing a strong acceptor 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene) malononitrile (TFM). By changing the number of TFM, we obtained two chromophores, which are named DTFM-DCF and STFM-DCF, respectively. Due to the large, rigid
-conjugated structure and strong electron-withdrawing capability of TFM, the maximum emission wavelengths of these molecules span from 681 to 755 nm in dichloromethane. Meanwhile, these two chromophores, which exhibit the property of thermally activated delayed fluorescence, have long-lived luminescence with
for STFM-DCF and
for DTFM-DCF in deaerated dichloromethane at room temperature.