Synthesis, Structure, and Spectral Properties of Perhalogenated Metalloporphyrins

In order to obtain perhalogenated metalloporphyrins, exhaustive bromination and chlorination of β-positions of nickel(II) and zinc(II) 5,10,15,20-tetra(2,6-dichlorophenyl)- and 5,10,15,20-tetra(2,6-difluorophenyl)porphyrins with N-bromosuccinimide and N-chlorosuccinimide in dimethylformamide have been carried out. When treating zinc(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetra(2,6-difluorophenyl)porphyrin and zinc(II) 2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetra(2,6-difluorophenyl)porphyrin with trifluoroacetic acid, the corresponding porphyrin ligands have been obtained. The synthesized compounds have been identified by electron absorption, 1H NMR spectroscopy, and mass spectrometry. The structures of halogen-substituted porphyrins and their zinc(II) complexes have been calculated by the DFT method. The introduction of bromine and chlorine atoms into the pyrrole rings of ortho-substituted porphyrins and their metal complexes leads to a distortion of the planar structure of molecules to a saddle-like one. The effect of β-halogenation on the fluorescence quantum yields of the synthesized compounds have been estimated. The quantum yield of β-chlorine-substituted porphyrin decreases by ~7 times as compared to the initial tetra(2,6-difluorophenyl)porphyrin, and that of its zinc porphyrinate decreases by ~15 times as compared to the initial complex. Complete quenching of fluorescence caused by the influence of heavy bromine atoms in the β-positions of the macrocycle is observed for both porphyrins and their metal complexes. Perhalogenated metalloporphyrins have increased n-conductivity and can be used to create new materials exhibiting nonlinear optical and catalytic properties.