New A3B porphyrins as potential candidates for theranostic. Synthesis and photochemical behaviour

Abstract The study reports a series of results obtained by synthesis, spectral and morphological analysis of new tetrapyrrolic structures: 5-(4-hydroxy-3-methoxyphenyl)-10,15,20- tris -(4-carboxymethylphenyl) porphyrin (P1.2), Zn(II)-5-(4-hydroxy-3-methoxyphenyl)-10,15,20- tris -(4-carboxymethylphenyl) porphyrin ( Zn(II)1.2 ) and Cu(II)-5-(4-hydroxy-3-methoxyphenyl)-10,15,20- tris -(4-carboxymethylphenyl) porphyrin ( Cu(II)1.2 ), as potential candidates for theranostics. Porphyrins were obtained by microwave synthesis under solvent-free conditions and characterized by elemental analysis, FT-IR, UV–Vis and NMR spectroscopies. The absorption properties of the synthetized compounds were studied in different solvents (ethanol, polyethylene glycol 200, dimethylsulfoxide, dichloromethane, chloroform). The spectral profile of the new porphyrins was completed by studying the fluorescence emission and singlet oxygen formation quantum yields. P1.2 and Zn(II)1.2 exhibit fluorescence while for Cu(II)1.2 the fluorescence emission is negligible. P1.2 and Zn(II)1.2 exhibited photodynamic therapy (PDT) acceptable values of singlet oxygen generation. In the case of Cu(II)1.2 this parameter is reduced ca. 5 times. For powdered samples of P1.2 adsorbed onto powdered PEG a detailed study was performed correlating the fluorescence emission intensity with sample absorption to determine the concentration range where aggregation does not occur. Fluorescence emission quantum yields and lifetimes were determined for all samples under study to determine the useful range of concentrations for PDT use. Atomic force microscope (AFM) studies were also made, which exhibit the aggregate species formation for high loadings of the porphyrin P1.2 adsorbed onto specific surfaces.