Colorimetric switching and sensing of CO2 based on reversible proton movement between the two heavy atoms in low barrier hydrogen bond in PDI radical anion/b-PEI hydrogen bonding complex

Abstract

The photophysical properties of the hydrogen bond complexes consisting of low-barrier hydrogen bond (LBHB) depend on their environmental condition. However, the stimuli responsive materials based on LBHB are still a challenging problem. Here, we report a novel material system which has high color response to CO2 based on the position changes of the proton between the two heavy atoms 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 and it shows the maximum absorption of 789 nm. Meanwhile, the maximum absorption of TFPDI-b-PEI appears at 561 nm with purple when CO2 is adsorbed in the branched polyethyleneimine. 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 molecule and amine groups in LBHB by interaction of CO2 with TFPDI-b-PEI. Further the TFPDI-b-PEI shows excellent color switching and colorimetric sensing performance for CO2 aqueous solution and its gas based on this hydrogen bond dynamic characteristic.