Studies on Zn(II) monohydroxyphenyl mesoporphyrinic complexes. Synthesis and characterization

A series of four Zn(II) complexes with asymmetrical porphyrinic ligands were synthesized: [5-(4-hydroxyphenyl)-10,15,20-triphenyl-21H,23H-porphinato]Zn(II) (Zn(II)TPPOHP), [5-(3-hydroxyphenyl)-10,15,20-triphenyl-21H,23H-porphinato]Zn(II) (Zn(II)TPPOHM), [5-(2-hydroxyphenyl)-10,15,20-triphenyl-21H,23H-Zn(II)-porphinato]Zn(II) (Zn(II)TPPOHO) and the well-known (5,10,15,20-tetraphenyl-21H,23H-porphinato]Zn(II) (Zn(II)TPP) as reference, in a 1:1 mole ratio. In all cases, the free-base porphyrin served as a tetradentate ligand through the four pyrrole nitrogen atoms. The complexes were characterized by elemental analysis, FTIR and UV-Vis spectroscopy, which fully confirmed the structure of the complexes. UV-Vis showed that the spectral absorption of the four complexes was blue-shifted by at least 50 nm compared to that of the free ligands. Also important structural data were obtained from several different NMR experiments (including H-1-NMR, C-13-NMR, DEPT, COSY, HMBC and HMQC). Influences of external substituents on the porphyrin ring were observed.