Synthesis, structure, electronic spectroscopy, photophysics, electrochemistry, and X-ray photoelectron spectroscopy of highly-electron-deficient [5,10,15,20-tetrakis(perfluoroalkyl)porphinato]zinc(II) complexes and their free base derivatives

The synthesis, optical spectroscopy, photophysical properties, electrochemistry, and X-ray photoelectron spectroscopy of a series of [5,10,15,20-tetrakis(perfluoroalkyl)porphinato]zinc(II) complexes and their free base analogs are reported. The title compounds were prepared by a condensation methodology that utilizes perfluoro-1-(2'-pyrrolyl)-1-alkanol precursors and employs continuous water removal throughout the course of the reaction to yield the meso perfluorocarbon-substituted porphyrins. The nature of the porphyrin-pendant meso-perfluoroalkyl group exerts considerable influence over the macrocycle's solubility properties. The structure of the monopyridyl adduct of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato]zinc(II) features an S4-distorted porphyrin core; X-ray data are as follows: P1̄ with a = 15.1330(5) Å, b = 19.2780(6) Å, c = 14.6030(4) Å, α = 110.220(2)°, β = 103.920(2)°, γ = 85.666(2)°, V= 3880.1(2) ų, d(calc) = 1.887 g cm^-3, and Z = 4. Electrochemical studies carried out on these porphyrin and (porphinato)zinc(II) complexes indicate that meso-perfluoroalkylporphyrins are among the most electron-deficient porphyrinic species known. X-ray photoelectron spectroscopy experiments corroborate the electron poor nature of these systems and evince extreme stabilization of the nitrogen 1 s orbitals, consonant with particularly effective removal of electron density from the macrocycle by the meso-perfluoroalkyl moieties that is modulated by σ-symmetry orbitals. The photophysical properties of these compounds differ from all other previously reported highly electron deficient porphyrin macrocycles in that they possess long-lived, fluorescent excited states; hence their optoelectronic features are consistent with a variety of excited-state electron-transfer quenching schemes in which both ¹ZnP* and ¹H2P* can be utilized as potent photooxidants.

Duke Scholars

Author Michael J. Therien Chemistry