An efficient synthetic approach towards new 5,5’-diaryl-2,2’-bipyridine-based fluorophores

An efficient approach has been developed for the synthesis of 5,5′-diaryl-2,2′-bipyridines via their 1,2,4-triazine analogues. The notable advantages of the present method are: The possibility of varying the aromatic substituents in the positions 5 and 5′ of bipyridine core and the possibility for obtaining 2,2′-bipyridines bearing a fused cyclopentene core to increase the solubility in organic solvents. These 5,5′-diaryl-2,2′-bipyridines exhibited an intense emission in a range of ca. 422–521 nm in acetonitrile solution; depending on the nature of the aromatic substituents and the presence of annulated cyclopentene fragments. Apart from that, the significant bathochromic shifts of the both absorption and emission maxima were observed in comparison with a number of previously described similar structures. In some cases the significant increasing of the fluorescence quantum yields took place.