Tatarets A. Organic luminophores based on squaric acid derivatives

The objects — squaric acid derivatives and squaraine dyes, the goal — elucidation of reaction regularities of squaric acid derivatives with CH-acid, cyanamide and thionating reagents; application of these reactions for synthesis of squaraine dyes; making of biomedical labels and probes on theit base. The methods — organic synthesis, X-ray analysis, mass-spectrometry, 1H-NMR, IR, molecular absorption and fluorescence spectroscopy, quantum chemical semi-empirical simulations. The work systematically investigates the reactions of dibutyl squarate and 3-butoxy-4-(2,3-dihydrohetarylidenemethyl)-3-cyclobutene-1,2-diones (monosquaraines) with CH-acidic compounds, nitrogen containing heterocyclic methylene bases, cyanamide and thionating reagents. Preparative methods for the synthesis of monosquaraines and squaraines of symmetrical and unsymmetrical structure were developed and novel dyes, where cyclobutenone oxygen was replaced by dicyanomethylene, cyanoacetate, nitroacetate, 1,3-indanedione, barbituric, thio-barbituric, cyanamide groups or sulfur were synthesized. Monosquaraine derivatives were found to be more reactive than squaric acid and dibuty squarate, which allowed us to synthesize squaraine dyes containing benzoxazole, 5-aryl-1,3-oxazole and 5-aryl-1,3,4-oxadiazole moieties. The correlation between spectral- and other photo-physical properties and the molecular structure of squaraines and monosquaraines was studied. We also found that thiosquaraines undergo a photoinduced hydrolysis to higher bright oxosquaraines, which substantially increases stability of the dyes brightness towards light exposure. New fluorescent probes and labels with improved characteristics were developed and tested for various biomedical applications.