Synthesis and photophysical properties of two novel branched pyridinium inner salt dyes

Abstract

Two new branched pyridinium inner salt dyes, 2,6-di[2-( N -ethyl-carbazole-3-yl)vinyl]- N -(3-sulfonatepropyl)pyridinium, inner salt ( 2 ) and 2,4,6-tri[2-( N -ethyl-carbazole-3-yl)vinyl]- N -(3-sulfonatepropyl)pyridinium, inner salt ( 3 ), with N -ethyl-carbazolyl as electron donor group and pyridine cation as electron acceptor group have been synthesized. Their single- and two-photon related fluorescence properties in various solvents have also been examined. These dyes exhibit stronger fluorescence emission relative to the corresponding linear counterpart and common pyridinium dyes with discrete cation and anion components. Three-branched organic dye 3 has a high fluorescence quantum yield as 0.12 and exhibits strong orange two-photon excited fluorescence at 608 nm in THF with large two-photon absorption cross-section being 606 GM. Two new branched pyridinium inner salt dyes with N -ethyl-carbazolyl as electron donor group have been synthesized. Three-branched organic dye has a high fluorescence quantum yield as 0.12 and exhibits strong orange two-photon excited fluorescence at 608 nm in THF with two-photon absorption cross-section being 606 GM. ► Two new branched pyridinium inner salt dyes were synthesized. ► The dyes exhibit strong yellow or orange fluorescence emission. ► Three-branched organic dye exhibits strong orange two-photon excited fluorescence in THF.