Fluorescence quenching properties of nitrobenzene derivative to poly(polyphenylene ethynylene carbazyl)

Poly(2, 5-dipentyloxyphenylene ethynylene carbazyl) (P) was synthesized with 2, 5-dimethoxy-1, 4-diethynylbenzene and 3, 6-diiodo-9-pentylcarbazole by Pd-catalyzed Sonogashira coupling reaction. The fluorescence quenched properties of P was influenced obviously by the structure and relative position of the substituting groups of nitrobenzene derivates. For the para-substituting nitrobenzene, the fluorescence quenching efficiency of quenchers increased with the increase of electron repulsion capability of the para-substituting group. And the fluorescence quenching efficiency reduced according to the sequence of o-NA, p-NA and m-NA under the same conditions due to the different electron withdrawing conjugated effect and inductive effect between amino- and nitro- group in nitroaniline isomers. Further study exhibits that the fluorescence quenching efficiency increases nonlinearly with the concentration of the quenchers.