PHOTOPHYSICAL PROPERTIES OF meso‐TETRAPHENYLPORPHYRIN and SOME meso‐TETRA(HYDROXYPHENYL)PORPHYRINS

Abstract

Abstract— The o‐, m‐, and p‐isomers of 5, 10, 15, 20‐ tetra(hydroxyphenyl)‐porphyrin have been of recent interest as potential second‐generation sensitisers in tumour phototherapy. Fluorescence spectroscopy, nanosecond laser flash photolysis and pulse radiolysis have been used to characterise the singlet and triplet excited states of tetraphenylporphyrin and the o, m‐, and p‐isomers of tetra(hydroxyphenyl)porphyrin. This has included evaluation of fluorescence yields and lifetimes, triplet spectra, lifetimes, oxygen quenching rate constants, extinction coefficients, and yields and singlet oxygen yields. Whilst the fluorescence quantum yields were low, the triplet yields were all 0.7 ± 10% and the singlet oxygen yields 0.6 ± 10%: all these parameters are in the ranges shown by other efficient porphyrin photosensitisers. The similar photophysical properties found for these compounds suggest that their differing tumour sensitising efficiencies are likely to be due to other factors.

Biological activities of phthalocyanines – XVI. Tetrahydroxy- and tetraalkylhydroxy zinc phthalocyanines. Effect of alkyl chain length on in vitro and in vivo photodynamic activities

“…Whereas, the o-, m-and p-isomers of THPP exhibited similar photophysical properties (Bonnett et al, 1988) large differences were noted in their biological activities, with the m-isomer showing the highest potency in sensitising tumours in vivo (Berenbaum et al, 1986). Unlike the disulphonated phthalocyanines and tetraphenylporphins, the THPP isomers are symmetric, lipophilic molecules lacking the characteristic amphiphilic properties of the disulphonated photosensitisers.…”

“…Berenbaum et al (1986) tested the ortho, meta and para isomers of meso-tetra(hydroxyphenyl)porphine (THPP) for their in vivo photodynamic activity and skin photosensitisation. Although the m-and o-THPP have very similar photophysical properties and similar absorbances at the wavelength used for PDT (Bonnett et al, 1988), the m-THPP is twice as effective as o-THPP in sensitising tumours, while o-THPP is four times as potent as m-THPP in sensitising skin. Doses of p-THPP and m-THPP that produce equal tumour necrosis are of the ratio 5:1, while their molar absorbances at the illuminating wavelengths are of the ratio 2:1.…”

Influence of Macrocycle Protonation on the Photophysical Properties of Porphyrins

“…[24] In case of the DP forms of Н 2 ТPP and its para-hydroxyl-substituted derivative Н 2 ТHPP, a more pronounced decrease in the Φ ISC value has been measured (0.30 and 0.29, respectively). [14,24,61,62] A slightly decreased Φ ISC value of 0.51 has been found for the water-soluble para-sulfonyl-substituted derivative Н 2 ТSPP. [21] It is clear that such a behavior of the Photophysical Properties of Protonated Porphyrins intersystem crossing quantum yield can be explained when multiple factors affect the rates of the intramolecular channels of excitation energy deactivation, with their competition determining the efficiency of the population of the triplet manifold in each particular case.…”

Photophysical characterization of the plant growth regulator 2-(1-naphthyl) acetamide

“…Individual singlet oxygen luminescence traces were signal averaged and fitted using a single exponential function to yield the luminescence intensity. The phosphorescence intensity was then plotted against the laser energy [27], which gave straight lines whose slopes were compared with that obtained from the reference biphenyl, yielding relative singlet oxygen quantum yields, ˚ . The relative ˚ values obtained for NAD (Table 7) show a dependence on solvent and vary between 0.097 and 0.396, in water and chloroform, respectively.…”

“…Singlet oxygen quantum yield, ˚ , was detected using timeresolved phosphorescence [27] by monitoring room temperature phosphorescence decay centered at 1270 nm using a Hamamatsu R5509-42 photomultiplier, cooled at 193 K in a liquid nitrogen chamber, following laser excitation of aerated NAD solutions in different solvents at 266 nm, with an Applied Photophysics flash kinetic spectrometer. Decays were then extrapolated to time zero and the initial phosphorescence signal studied as a function of laser intensity.…”