Irregular behavior of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin in Langmuir–Blodgett films

Multilayer Langmuir–Blodgett films containing 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (PFP) in octadecylamine and in fatty acid matrices were prepared. The films revealed relatively long fluorescence lifetimes with an irregular concentration dependence: the longer lifetime corresponded to the higher concentration of PFP. Fluorescence decay-associated spectra indicated that energy migration contributed to the relaxation of the singlet excited state at all concentrations studied. In comparison with solutions, the absorption spectra of the films revealed a distinct band narrowing and an increase in molar extinction of the Soret band. Presumably, PFP formed unusually uniform structures, a kind of highly ordered aggregates, in the plane of monolayers.