The present invention relates to new 6-substituted-7-Hydroxy-4-(methylthio)-2-oxo-2Hchromene- 3-carbonitriles of the general formula I which can be used potentially as fluorescent probes, diagnostics, fluorescent tags, for staining of vacuoles of virus particles, bacterial particles, virus components, biological cells (such as animal cells, plant cells, bacteria, or yeast), or cellular components in fluorescence-based imaging and/or analysis in fixed or live cell. The invention also relates to the method of preparation of the said compound.