Yield of intersystem (singlet–triplet) crossing in phthalocyanines evaluated on the basis of a time in resolved photothermal method

Triplet Thermal Relaxation Study as a Probe of Weak Interdimers of Porphyrin Derivatives

“…The first one could be charge transfer in the pyridyl porphyrin-polymer system; constancy of the thermal relaxation times of 3 I and 3 II clearly indicates that thermal relaxation is almost unaffected by the presence of the polymer. In aromatic molecules with the pyridyl units, the intramolecular charge transfer could occur as shown in a classic paper of Levinson et al [10] for pyridocyanine and triplet enhancement can be induced by such interactions [46]. Comparison of the data presented in Tables 1 and 2 for the samples in DMSO with those for aggregated porphyrin species in water [23,24] indicates enhancement of intersystem crossing in these dye-polymer systems.…”

“…The photoacoustic measurements in the range of 300 nm to 800 nm were carried out with a one-beam MTEC photoacoustic spectrometer [46]. Light modulation frequencies of the light beam were (8, 10, 15, 20, and 30) Hz at a constant phase shift.…”

“…The kinetics of photothermal processes and triplet population were measured with the use of LIOAS [46,47]. The samples were illuminated by a flash GL-3300/GL301 nitrogen laser (Photon Technology Int.…”

“…These processes could be phosphorescence and thermal relaxation processes occurring in microseconds. Moreover, we cannot exclude processes such as, for example, charge redistribution upon covalent linkage to the polymer (rather weak on the basis of our absorption and fluorescence examinations), generation of singlet oxygen (almost excluded since our LIOAS experiments were performed in a nitrogen atmosphere), and deformation of the molecular skeleton as well as steric effects leading to conformation and aggregation [46].…”

Nonlinear Optical Absorption of Organic Molecules for Applications in Optical Devices

“…On the other hand, the intersystem-crossing lifetime (1.5 ns) is shorter than the typical values reported for porphyrins and phthalocyanines. (Frackowiak et al, 2001, Shirk et al, 1992. This short intersystem-crossing lifetime indicates an efficient singlet-triplet conversion, which makes Chlorophyll A suitable for applications as a PDT sensitizer.…”