Compared with the non-fluorinated molecule DIPT-IC, the absorption of the fluorinated molecule DIPT-ICF showed a redshift of 72 nm, which could be ascribed to the enhanced the intramolecular charge transfer (ICT) effect induced by the electron-withdrawing fluorine atoms . Density functional theory (DFT) calculation reveals that DIPT-ICF exhibits smaller energy gap than DIPT-IC (1.844 eV vs 1.879 eV) (Fig. ), which matched well with the absorption data. Moreover, the well overlapped highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) electron density distribution suggests a favorable electron transition, which benefits a high molar absorptivity. Indeed, the molar absorptivity of DIPT-ICF is as high as 8.23×10 4 M -1 cm -1 , which is higher than that of DIPT-IC 2.43×10 4 M -1 cm -1 , suggesting that the introduction of fluorine atom helps to improve the molar absorptivity (Fig. ). Therefore, the introduction of fluorine atom benefits both the absorption redshift the molar absorptivity enhancement. It is worthy to note that molar absorptivity of over 80000 M -1 cm -1 is rather high for NIR-II luminogens, which will contribute greatly to the brightness of the contrast agents .