Polythiophene based fluorescent probe for copper ions with high sensitivity

Two new conjugated polymers poly{3‐({4‐[(2‐hydrazino‐2‐oxoethyl)(methyl)amino]cyclohexylidene}methyl)thiophene}( P1 ) and poly{3‐({4‐[(3‐hydrazino‐3‐oxopropyl)(methyl)amino]cyclohexylidene}methyl)thiophene}( P2 ) were synthesized, and their optical properties were investigated. P1 exhibited excellent selectivity toward Cu 2+ ions in 50% water solution, the fluorescence color of P1 changed distinctly from greenyellow to colorless in the presence of Cu 2+ under UV‐light, while introduction of other metal ions could not induce such significant variation. Moreover, highly sensitive detection of Cu 2+ ions was demonstrated in 90% water solution. Its high metal‐chelating capability allowed Cu 2+ recognition with a detection limit of 3.2 × 10 −10 M. These results indicated that this kind of nonionic polymer containing multidentate ligand could be used as a highly selective and sensitive chemosensor for Cu 2+ detection. The proposed binding mode of P1 with Cu 2+ was supported by DFT calculation using Gaussian 03. Unlike P1 , P2 showed no obvious fluorescent change in the presence of various metal ions due to its space steric hindrance resulted from N/O distribution on the side chain of P2 . © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 42440.