Synthesis and spectral–luminescent studies of novel 4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-a]thieno[2,3-d]pyrimidinium styryls as fluorescent dyes for biomolecules detection

A series of novel 4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-a]thieno[2,3-d]pyrimidinium and 5-oxo-1,2,3,5-tetrahydropyrrolo[2,1-b]quinazolinium styryl dyes were synthesized. For preparing of studied dyes the standard method of styrylcyanines synthesis was modified. Spectral–luminescent properties of obtained dyes in free state and in the presence of nucleic acids and BSA were studied. It was shown that p-dimethylaminostyryls based on 4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-a]thieno[2,3-d]pyrimidinium with aliphatic substituents in 2 and 3 positions demonstrated RNA-binding preference. These dyes in the presence of RNA significantly enhance emission intensity and could be used as RNA-specific fluorescent probes. Besides, the fluorescence emission after two-photon absorption of dye–RNA complexes in buffer solutions was measured.