Interaction of meso-tetrakis (p-sulfonatophenyl) porphyrin (TSPP) with pyrimidines: A steady state and time-resolved fluorescence quenching study

Fluorescence quenching of meso-tetrakis (p-sulfonatophenyl) porphyrin (TSPP) by certain pyrimidines has been investigated by using steady state and time-resolved fluorescence techniques. The pyrimidines used are uracil, 5-fluorouracil, 5-chlorouracil, 5-bromouracil, 5-iodouracil and 5-aminouracil. The quenching was found to obey the Stern–Volmer equation and the corresponding Stern–Volmer plots were linear from both steady state and time-resolved measurements, indicating dynamic nature of quenching and the bimolecular quenching rate constants (kq) agreed well. Electron transfer from TSPP to pyrimidines were confirmed by the calculation of free energy change (ΔGet) using Rehm–Weller equation.