Polymethine dyes derived from the boron difluoride complex of 3-acetyl-5,7-di(pyrrolidin-1-yl)-4-hydroxycoumarin

A boron difluoride complex of 3-acetyl-5,7-di(pyrrolidin-1-yl)-4-hydroxycoumarin was synthesized and converted into polymethine dyes which included an anionic, symmetric cyanine and several merocyanine compounds. The spectral luminescent behaviour of the dyes was studied. As the electron-withdrawing ability of the 2,2-difluoro-1,3,2-dioxaborine ring was significantly reduced by the two pyrrolidino groups on the latter nucleus, the newly synthesized dyes exhibited changes in spectral parameters and much increased resistance to hydrolysis.