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 ( k q) agreed well. Electron transfer from TSPP to pyrimidines were confirmed by the calculation of free energy change ( ΔG et) using Rehm–Weller equation.