Synthesis, Photochemical and Photoinduced Antibacterial Activity Studies of meso-Tetra(pyren-1-yl)porphyrin and its Ni, Cu and Zn Complexes

Tamara Zoltan

doi:10.3797/scipharm.1003-13

Abstract

The synthesis of the meso-tetra(pyren-1-yl)porphyrin (1) was successfully accomplished by means of the pyrrole condensation with pyrene-1-carb-aldehyde in acidic media. Its metallization was carried out in an almost quantitative yield to obtain the corresponding complexes of Ni(II) (2), Cu(II) (3) and Zn (4). Their photophysical properties such as fluorescence quantum yield and energy transfer to oxygen for an efficient generation of singlet oxygen were determined. Their photophysical and photochemical properties were compared with those of other similar porphyrin derivatives such as tetraphenylporphyrin and tetranaphthylporphyrin. Photochemical studies on their effectiveness as photosensitizer were carried out by means of the photoinduced oxidation of aromatic alcohols like α-naphthol to naphthoquinone. The antibacterial photoactivity assay for compounds 1–4 was testeted against Escherichia coli (ATCC 8739) and its proliferation and viability were measured by chemiluminescence. An efficient inactivation of E. coli was observed. This was more efficient for compounds 2 and 3, following the direct relationship to high generation of singlet oxygen by these compounds.

Highlights

The most important family of photosensitizers for the production of singlet oxygenderives from porphyrins and chlorophylls, originating high singlet oxygen yields (1O2)
The interaction of porphyrin derivatives with oxygen under the influence of light, as well their photostability, has been a matter of great interest. The use of these compounds in the field of photodynamic therapy [6, 7] as well as photo-oxidation sensitizers stimulating their use the highly efficient intersystem crossing to its triplet state and its long life time which in turn is responsible for the high quantum yield of singlet molecular oxygen
The photosensitized generation of singlet oxygen can be used for oxygenation of variable intensity as a function of Φ1O2 in the process of degradation of organic or biological compounds in residual water and as new alternatives for photo-inactivation of microorganisms [15–19]. In this way we propose and used a model system for the sensitive photo-oxidation of an aromatic alcohol, α-naphthol to naphthoquinone by compounds 1 to 4, verifying in the course of this work the efficiency of this conversion

Summary

Introduction

The most important family of photosensitizers for the production of singlet oxygenderives from porphyrins and chlorophylls, originating high singlet oxygen yields (1O2). Various other applications for such compounds, in the presence of light, outside the medical domain demand that the persistence of the porphyrin be critically tied to a minimal challenge by singlet oxygen, an especial stability toward singlet oxygen. This prompted us to carry out a study on the photochemically excited estates of synthetic tetra-arylporphyrins and their metallic complexes, for the optimization of photoinduced oxidation of organic compounds

Results

Discussion

Conclusion