Novel Alexa Fluor fluorescent cyanine dye as well as preparation method and application thereof

The invention discloses a novel Alexa Fluor fluorescent cyanine dye as well as a preparation method and application thereof. The structural general formula (I) of the novel Alexa Fluor fluorescent cyanine dye is as shown in the specification, wherein n1 is equal to 1 or 2, n2 is equal to any integer ranging from 1 to 5. A squaric acid bridge ring is successfully introduced into the fluorescent cyanine dye Alexa Fluor to obtain a series of improved Alexa Fluor fluorescent cyanine dyes, and the heat stability is obviously improved in comparison with that of the existing fluorescent cyanine dye Alexa Fluor, the Alexa Fluor fluorescent cyanine dye can be applied to marking and positioning tissues, cells and biomolecules in biological chemistry analysis or preparing a fluorescence mark reagent.