Novel 5-benzazolyl-10,15,20-triphenylporphyrins and β,meso-benzoxazolyl-bridged porphyrin dyads: Synthesis, characterization and photophysical properties

摘要

Novel 5-benzazolyl-10,15,20-triphenylporphyrins and β,meso-benzoxazole-linked diporphyrins were synthesized through La(OTf)3 catalyzed reaction of newly prepared 5-(3,4-diaminophenyl)-10,15,20-triphenylporphyrin or 5-(3-amino-4-hydroxyphenyl)-10,15,20-triphenylporphyrin with aromatic aldehydes in 1,2-dichlorobenzene. On metalation with zinc acetate, freebase β,meso-benzoxazole-linked diporphyrin was successfully converted to the Zn—Zn diporphyrin complex in good yield. The synthesized porphyrin analogues were characterized using electronic absorption, IR and ~1H NMR spectroscopy in addition to mass and elemental analyses. The fluorescence studies of 5-benzazolyl-10,15,20-triphenylporphyrins showed efficient intramolecular energy transfer from the pyrene and fluorene subunits to the porphyrin core. In addition, the fluorescence quenching observed in β,meso-benzox-azolyl-bridged porphyrin dyads was attributed to the possible nonplanarity of a component of the diporphyrins. The freebase-Ni diporphyrin complex underwent strong emission quenching in comparison to that of freebase diporphyrin and dizinc diporphyrin analogues.