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

Boscencu Rica (Carol Davila' University of Medicine and Pharmacy, Faculty of Pharmacy, Inorganic Chemistry Department, Bucharest, Romania)
Socoteanu Radu (Romanian Academy, Institute of Physical Chemistry 'I.G. Murgulescu', Bucharest, Romania)
Oliveira Anabela S. (Centro de Química-Física Molecular, Complexo Interdisciplinar, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisbon, Portugal)
Ferreira Vieira Filipe Luis (Centro de Química-Física Molecular, Complexo Interdisciplinar, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisbon, Portugal)

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 1H-NMR, 13C-NMR, DEPT, COSY, HMBC and HMQC). Influences of external substituents on the porphyrin ring were observed. .

Keywords: asymmetric porphyrins, Zn(II) porphyrin complexes, sensitizers for photodynamic therapy, molecular absorption coefficients, NMR spectroscopy