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 ([O1---H1-N1]-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 Al3+, Ni2+ and Cd2+ 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 ([O1--H1--N1]-1 and [O1---H1-N1]-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 Al3+.

Automated summary

The photophysical properties of low-barrier hydrogen bond (LBHB) hydrogen bonded complexes depend on their environmental conditions. However, developing stimuli responsive materials based on LBHB is still challenging. This study presents a novel material system with 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. TFPDI-b-PEI shows excellent colorimetric sensing performance for Al3+ through adjusting the interaction between the surrounding molecules and amine groups in LBHB by the interaction of metal ions with TFPDI-b-PEI.