Synthesis and Functional Properties of Fluorinated Phosphonate-Substituted Porphyrins: Excellent Photosensitizers and...

Fluorinated porphyrins have attracted considerable attention in PDT, sensing and catalysis. Guided by demands for functional porphyrins with tunable electronic properties, high photostability, and controlled supramolecular organization, we report a synthetic approach to meso-tetrakis[4-(diethoxyphosphoryl)-2,3,5,6-tetrafluorophenyl]porphyrin (H₂TF₄PPP), which combines the advantages of diethyl phosphonate and fluorine substituents within a highly symmetrical porphyrin molecule. X-ray diffraction analysis of H₂TF₄PPP reveals that diethyl phosphonates govern the crystal packing, while the macrocycles avoid π-π stacking. Zn(II) and Pd(II) complexes with H₂TF₄PPP were prepared in high yields. In contrast, insertion of In(III) ions exhibiting strong Lewis acidity was accompanied by partial hydrolysis of phosphonate groups. H₂TF₄PPP and its Zn(II) and Pd(II) complexes efficiently generate singlet oxygen displaying a good solubility in various organic solvents. The noble-metal-free porphyrin H₂TF₄PPP surpasses Pd(II) complex of non-fluorinated analogue (PdTPPP) in photocatalytic performance, enabling sustainable oxidation of sulfides to sulfoxides with oxygen. H₂TF₄PPP forms a stable Langmuir monolayer which can be transferred onto solid substrates, yielding dense single-layer films containing fiber-shaped nanoparticles. The films thus obtained are emissive and their photostability surpasses that of H₂TPPP films. Water-soluble porphyrins H₂TF₄PPP-A and PdTF₄PPP-A with phosphonic acid groups were also prepared and briefly investigated.