Excited-state solvation dynamics of meso-tetrakis （4-sulfonatophenyl） porphyrin in solid imidazolium-sulfonate-based ionic liquids

The steady-state absorption and fluorescence emission positions of diprotonated meso-tetrakis（4-sulf- onatophenyl） porphyrin （H4TPPS2 ） are dependent on the polarity of the selected two solid ionic liquids （ILs） and are red-shifted with the increase of cation size. The solvation dynamics process of H4TPPS2- in these ILs occurs on two well-separated time scales. The short components with 121.2-128.6 ps arise from the local motion of the ion-pairs in close proximity to the porphine core, and the long components with 1056.6-1261.8 ps are due to the collec- tive translation motions of the ion-pairs. The dynamic Stokes shifts and the relaxation times increase with the increasing cation size of the ILs.