New 2,2-difluoro-1,3,2(2H)oxazaborines and merocyanines derived from them

Synthetic methods have been developed to prepare oxazaborines, the azaanalogues of 2,2-difluoro-1,3,2(2H)dioxaborines, which can form merocyanine dyes. The first oxazaborine merocyanines with the isomeric position of the coordinating nitrogen atom have also been obtained. Comparing the spectral properties of donor-acceptor dioxa- and oxazaborine dyes, it is seen that substitution of the 3-O atom by the NH group in the chelate ring has a slight effect on absorption and fluorescence band positions but causes the intensity redistribution between the 0–0 and 0–1 vibronic absorption peaks and thus induces a change in the absorption band shape due to the enhanced solvation of oxazaborines. Substitution of the 1-O ring atom by the NPh group leads to a bathochromic shift and a manifold increase in the fluorescence quantum yield for the corresponding boron chelate dyes.

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► Oxazaborine merocyanines.
► The 3-aza and 1-aza analogues of 1,3,2(2H)dioxaborines have been synthesized.
► The two series of merocyanine dyes have been derived from new oxazaborines.
► The spectroscopic effects of the O-to-N substitution in new dyes have been studied.
► The manifold increase in the fluorescence quantum yield for some new dyes was found.