The solvation dynamics and rotational relaxation of protonated meso-tetrakis(4-sulfonatophenyl)porphyrin in imidazolium-based ionic liquids measured with a streak camera

For the steady-state behavior of diprotonated tetrakis(4-sulfonatophenyl)porphyrin (H4TPPS2-) in five imidazolium ionic liquids (ILs), the absorption positions of H4TPPS2- primarily depend on the constituent ions of the ILs whereas the emission positions of H4TPPS2- strongly depend on the polarity of the ILs. The fluorescence spectra of H4TPPS2- with different excitation wavelengths show no red-edge effect in our system. The dynamics of H4TPPS2- in ILs is further studied with a streak camera, and the relaxation process of ILs occurs on two different time scales. The short lived component attributed to the local motion of the cations and the anions around the porphine core varies from 32 to 196 ps. The long lived one originated from the collective diffusive motions of the cations and anions varies from 460 to 1072 ps. The average solvation time depends on the viscosity of the ILs. The rotational relaxation times of H4TPPS2- decrease as the viscosity of the ILs decreases.

Circular dichroism studies on intermolecular interactions of amphotericin B in ionic liquid-rich environments

Aggregation of amphotericin B (AmB) in an ionic liquid-rich environment was investigated using circular dichroism (CD) spectroscopy. It was found that nature of the ionic liquids' anion had a strong impact not only on the aggregation of AmB, but more importantly on the nature of AmB aggregates, as observed in the asymmetry of the exciton couplet of the aggregate in CD spectra. Unique CD signals for AmB aggregates were observed in three different 1-butyl-3-methylimidazolium ionic liquid solutions: [C4 -mim]Br favored the formation of AmB aggregates that were similar to those found in water, whereas [C4 -mim]BF4 and [C4 -mim]NO3 produced AmB aggregates that were different from each other and those found in water. The obtained results suggest that the designer solvent ability of ionic liquids could be expanded to address numerous intermolecular processes.