Novel chemosensory materials based on polyfluorenes with 2-(2′-pyridyl)-benzimidazole and 5-methyl-3-(pyridin-2-yl)-1,2,4-triazole groups in the side chain

Polyfluorenes with 2-(2′-pyridyl)-benzimidazole (P1, P2 and P4) and 5-methyl-3-(pyridin-2-yl)-1,2,4-triazole (P3) groups in the side chain were synthesized by Suzuki polycondensation. The responsive properties of polymers on metal ions and H+ were investigated by absorption and emission spectra. The fluorescences of polymers (P1–P4) were completely quenched upon the transition metal ions such as Co2+, Ni2+, Fe3+ and Ag+ due to the enhanced electronic communication properties of conjugated polymers. The obvious differences to Ni2+ ion responsive sensitivity were observed between P1 and P4 polymers. The fluorescences of P1 and P4 were quenched to 50 (I0/I) and to 22 (I0/I) upon the addition of a Ni2+ solution of 3.2 × 10−6 M, as well as 5.0 × 10−6 M, respectively, owing to the different conjugated backbone. The fluorescences of P2 and P3 were completely and hardly quenched upon the addition of a Al3+ solution of 1.0 × 10−4 M, respectively, owing to the different receptors in the side chain. P2 showed good selectivity to Ni2+ ion in the range of quencher concentration as low as 5 ppm, owing to the different chelating abilities of receptor with ions. Cu2+ and Mn2+ ions hardly quenched the fluorescences of polymers (P1–P4), which were different from the oligopyridyl-functionalized conjugated polymers. The results further opened the opportunities to develop the tailored sensory materials through the appropriate alteration of receptors in the side chain and the conjugated backbone.