Perfluorinated porphyrazines. 3. Synthesis, spectral-luminescence and electrochemical properties of perfluorinated octaphenylporphyrazinatozinc(II)

Abstract

Octakis(pentafluorophenyl)porphyrazinatozinc(II), [ZnPAF40], has been prepared by template cyclotetramerization of perfluorinated α,β-dicyanostylbene in the presence of ZnCl2 in a melt. Influence of perfluorination of phenyl rings on spectral, electrochemical and acid-base properties of porphyrazine macrocycle is revealed by comparison with octaphenylporphyrazinatozinc(II), [ZnPA], which was prepared similarly from trans-α,β-dicyanostylbene. B3LYP DFT calculations show that perfluorination of phenyl rings stabilizes the frontier molecular orbitals of the porphyrazine macrocycle and slightly increases the HOMO-LUMO gap. As a result the reduction of the macrocycle is strongly facilitated and observed for [ZnPAF40] at 0.26 V vs Ag/AgCl, by 0.56 V in the less negative region as compared to [ZnPA]. Perfluorination leads to hypsochromic shift of the Q-band (lowest ππ* transition) in the electronic absorption spectra from 633 nm for [ZnPA] to 623 nm for [ZnPAF40] and increases the fluorescence quantum yield ФF from 0.12 to 0.19, respectively (values in THF). [ZnPAF40] has higher efficiency in generation of singlet oxygen (ФΔ = 0.60) than [ZnPA] (ФΔ = 0.37) (in THF). Introduction of 40 fluorine atoms decreases the basicity of the porphyrazine macrocycle almost by 3 orders of magnitude according to spectrophotometric titration study in CH2Cl2-CF3COOH medium.