Fluorescence Anisotropy in Radachlorin and Chlorin e6 in Water–Methanol Solutions under One- and Two-Photon Excitation

The fluorescence anisotropy of photosensitizers Radachlorin and chlorin e6 was studied using the time-resolved single photon-counting technique under one- two-photon excitation within Soret absorption band. A very small negative observed in both one-photon vicinity maximum wavelength range 395–405 nm. Meanwhile, same spectral demonstrated high with value about 0.43. drastic difference parameters at modes suggested to be due different symmetries tensors when tensor components have comparable values. variation wavelengths 375–425 nm nonlinear dependence e6, opposite tendencies excitation. data obtained suggest that 405 often utilized FLIM experiments is not sensitive therefore cannot used for determination anisotropy/rotational diffusion time these molecules. can provide accurate rotational time. At time, evaluation lifetimes standard schematic where polarization taken into account.