Photophysical properties of 5,10,15,20-tetrakis(m-hydroxyphenyl)porphyrin (m-THPP), 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (m-THPC) and 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC): a comparative study

Abstract

For the tumour photosensitisers m-THPP, m-THPC, and m-THPBC in methanol the following photophysical properties have been measured: absorption and fluorescence spectra, E_S, Stokes shift, Φ_f, Φ_T, τ_T, dioxygen quenching rates, and Φ_Δ for air-saturated and oxygen-saturated solutions. The properties of the first excited triplet state are quite uniform across this series. The quantum yields of singlet oxygen formation are high, being 0.43–0.46 in air-saturated methanol, and 0.59–0.62 in oxygen-saturated methanol. For a constant substitution pattern and a standard given light dose, tumour photonecrosis in vivo appears to parallel the product of drug dose and the molar extinction at the irradiation wavelength in the red region of the visible spectrum.