A triphenylamine-functionalized fluorescent oraanic polymer as a turn-on fluorescent sensor for Fe3+ ion with high sensitivity and selectivity

A triphenylamine-functionalized A(3)B(2)-type covalent organic polymer (TPACOP) was synthesized by the palladium-catalyzed Sonogashira polycondensation reaction from tris(4-ethynylphenyl)amine and 4-bromo-N-(4-bromo-2-methoxybenzylidene)-2-methoxyaniline. The obtained polymer possessing amorphous structure and good thermal stability exhibited strong yellow-green luminescence with an emission band at 498 nm. It is worth noting that the polymer also shows selective turn-on fluorescence response to Fe3+ ion over a variety of other competing metal ions such as Na+, K+, Ca2+, Mg2+, Ba2+,Mn2+, Cr3+, Cu2+, Ni2+, Zn2+, Co2+, Al3+. The fluoresent detection limit of TPA-COP sensor for Fe3+ in solution was 4.3 x 10(-7) M. Furthermore, the proposed sensing mechanism should result from complexation between tridentate-coordinated Schiff base sites and Fe3+ ion, which was further investigated by fluorescence titration, H-1 NMR and IR measures, together with fluorescence lifetime analysis.