Detecting metal ions by the color change in perylene diimide radical anion/b-PEI complex

The photophysical properties of the hydrogen bonded complexes consisting of low-barrier hydrogen bond (LBHB) depend on their environmental conditions. However, the stimuli responsive materials based on LBHB are still a challenging problem. Here, we report a novel material system which has a high color response to metal ions based on the position changes of the proton between the two heavy atoms involved in the low barrier hydrogen bond. Perylene diimide radical anion/branched polyethyleneimine hydrogen bonding complex (TFPDI-b-PEI) linked by low-barrier hydrogen bond ([O 1 -----H 1 ---N 1 ] −1 ) is obtained. The spectral responses of TFPDI-b-PEI to different metal ions are investigated in DMF and aqueous solutions by UV–Vis spectrophotometry . The results show that TFPDI-b-PEI can recognize Al 3+ , Ni 2+ and Cd 2+ by the blue shift of characteristic absorption peak (from 789 nm to 565 nm) and the change of absorbance. In essence, the geometry of LBHB in TFPDI-b-PEI can switch between two types of hydrogen bond ([O 1 ----H 1 ----N 1 ] −1 and [O 1 -----H 1 ---N 1 ] −1 ) via adjusting the interaction between the surrounding molecules and amine groups in LBHB by interaction of metal ions with TFPDI-b-PEI. In addition, based on this hydrogen bonding dynamic property, TFPDI-b-PEI exhibits excellent colorimetric sensing performance for Al 3+ .