Synthesis of a New Water-Soluble Polymeric Probe and its Fluorescent Properties for Ratiometric Measurement of Near-Neutral pH

• Published in: Analytical letters 2004-12, Vol.37 (14), p.2937-2948
• Main Authors: Dong, Suying, Ma, Huimin, Li, Xiaohua, Sun, Ming, Duan, Xuejun
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Fluorescence; Ratiometric measurement; Spectrometric and optical methods; Water-soluble polymeric fluorescent probe
• ISSN: 0003-2719; 1532-236X
• DOI: 10.1081/AL-200035845

A new water-soluble polymeric fluorescent probe, poly[allylamine-co-N-4-chloro-6-(4-methylcoumarin-7-oxy)-1,3,5-triazinylallylamine] (PA-TMC), has been designed and characterized for near neutral pH measurement in dual-excitation ratio application. The probe was synthesized by using cyanuric chloride as a linker, 7-hydroxy-4-methylcoumarin as a fluorophore, and polyallylamine as a water-soluble molecular scaffold. It showed a large pH-dependent shift of excitation peak from 320 to 360 nm with no change of emission wavelength of 448 nm. The pK a value of the probe was 7.56, and the ratio R (I 360 /I 320 ) of fluorescence intensities at the two excitation wavelengths of 360 nm and 320 nm was directly proportional to pH values over the range 6.8-8.5, which may be suitable for the pH monitoring of near-neutral systems. Spectroscopic properties of the probe were also compared with the corresponding low molecular weight 7-(4,6-dichloro-1,3,5-triazinoxy)-4-methyl-coumarin (TMC). The results showed that the incorporation of TMC into a water-soluble polymer bearing a large number of hard base ligands offers both considerably improved selectivity for H + and solubility in water, suggesting that such measure may be useful for preparing other probes with special functions.