A high quantum yield two-way conversion luminescent oligomer: 1,4-butanediol-bis(5-carbonyl-3-carbethoxy-2-pyrazoline)

Abstract

Oligomers as fluorescent macromolecules are of significant importance and are fairly attractive for high quantum yield two-way conversion luminescence. We report a high conversion rate (Φ_F = 0.5184) for a fluorescent oligomer, 1,4-butanediol-bis(5-carbonyl-3-carbethoxy-2-pyrazoline). It was prepared by the novel cyclopolycondensation of 1,4-butanediol-bis(5-carbonyl-3-carbethoxy-2-pyrazoline), a chromophore with good fluorescence (Φ_F = 0.0573). After polymerization, a green fluorescent protein (GFP)-mimetic structure was formed, in which a methylene chain (–CH₂–CH₂–CH₂–CH₂–) as a flexible group is beneficial due to its folding, and an azo group sits in the rigid pyrazoline ring because of a resonance effect. These factors collectively contribute to the excellent efficiency of the fluorescence performance of the oligomer. Additionally, the oligomer exhibited a weak red shift and a significant fluorescence enhancement compared with the monomer, and we achieved good quality live-cell imaging. The oligomer also allowed for the enhancement of fluorescence intensity through the two-wavelength excitation of a cell rather than increasing the dosage of the dye or the power of the laser.