Water-soluble fluorophores from triphenylbene

Abstract

This research involves the design and synthesis of three new fluorophores. All of these compounds have the same 1,3,5-triphenylbenzene core and phenyleneethynylene repeating units but different peripheral groups. The fluorophore structures were composed by Sonogashira reaction between the core and peripheral parts with ester functional groups such as ethyl 4-ethynylbenzoate, diethyl 3-ethynyl-isophthalate, and ethyl 5-iodosalicylate. Upon hydrolysis, the water-soluble fluorophores 1-3 were obtained. The photophysical studies in 10 mM phosphate buffer pH 8 revealed that these compounds have maximum wavelength of absorption between 310 and 318 nm and can emit the light in the wavelength range of 375-465 nm. The emission efficiencies of compound 1, 2, and 3 are 21.4, 47.2, and 0.70%, respectively. In addition, it was found that the fluorescent signal of compound 3 with salicylate peripheries could be selectively quenched by Cu²⁺ ion. In the absence of surfactant, the quenching constant is 1.62x10⁶ M⁻¹. This value can be increased up to 1.50x10⁷ M⁻¹ by the addition of surfactant such as Triton X-100.