Abstract: The present invention relates to compounds of the formula (I), a process for its preparation and its use as fluorescent dye that absorbs light emitted from an irradiation source and emits light different from that of the irradiation source and having a wavelength in the range from 680 to 950 nm; in photovoltaic applications; or as semiconductor in organic electronic applications; as laser dye, in an ink for machine readability and/or security applications or for the laser-welding of plastics; or for brand protection or as marker for liquids. The compounds of formula (I) may have a high fluorescence quantum yield, a high molar extinction coefficient, a high solubility and stability in the application medium, good storage stability and/or good detectability even in very small amounts in the correspondingly marked liquids.