A novel derivative of acetylene Kaede protein chromophore (Z)-2-((4-(diethylamino) phenyl) ethynyl)-5-(4-hydroxybenzylidene)-3-methyl-3,5-dihydro-4H-imidazol-4-one was synthesized by a modified Sonogashira reaction. In comparison with the classical GFP chromophore analog, the compound exhibits a prominent shift of absorption and emission maxima to the long-wavelength region. The value of Stock’s shift of the newly synthesized compound reached almost 150 nm.