This paper deals with a series of new unsymmetrically substituted mesoporphyrins: 5-(2-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHO), 5-(3-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHM), 5-(4-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOHP), 5-(2-hydroxyphenyl)-10,15,20-tris-butyl-21,23-H-porphyrin (TBPOHO), and their parent nonsubstituted compounds, respectively, 5,10,15,20-tetrakis-phenyl-21,23-H-porphyrin (TPP) and 5,10,15,20-tetrakis-butyl-21,23-H-porphyrin (TBP). Several photophysical studies were carried out to access the influence of the unsymmetrical substitution at the porphyrinic macrocycle on porthyrin's photophysical properties, especially porthyrin's efficiency as singlet oxygen sensitizers. The quantum yields of singlet oxygen generation were determined in benzene (ΦΔ(TPP) = 0.66 ± 0.05;ΦΔ(TPPOHO) = 0.69 ± 0.04;ΦΔ(TPPOHM) = 0.62 ± 0.04;ΦΔ(TPPOHP) = 0.73 ± 0.03;ΦΔ(TBP) = 0.76 ± 0.03;ΦΔ(TBPOHO) = 0.73 ± 0.02) using the 5,10,15,20-tetraphenyl-21,23-H-porphine (ΦΔ(TPP) = 0.66) and Phenazine (ΦΔ(Phz) = 0.83) as reference compounds. Their fluorescence quantum yields were found to be (Φf(TPPOHO) = 0.10 ± 0.04;Φf(TPPOHM) = 0.09 ± 0.03;Φf(TPPOHP) = 0.13 ± 0.02;Φf(TBP) = 0.08 ± 0.03 andΦf(TBPOHO) = 0.08 ± 0.02 using 5,10,15,20-tetraphenyl-21,23-H-porphine as referenceΦf(TPP) = 0.13). Singlet state lifetimes were also determined in the same solvent. All the porphyrins presented very similar fluorescence lifetimes (mean values ofτS(withO2, air equilibrated) = 9.6 ± 0.3 nanoseconds and (withoutO2, argon purged) = 10.1 ± 0.6 nanoseconds, resp.). The phosphorescence emission was found to be negligible for this series of unsymmetrically substituted mesoporphyrins, but an E-type, thermally activated, delayed fluorescence process was proved to occur at room temperature.

No abstract

Unsymmetrical porphyrin, 5-(3-hydroxyphenyl)-10,15,20-tris-(4-carboxymethylphenyl)-21,23-H-porphine (TCMPOHM) and also the parent symmetrical compound 5,10,15,20-meso-tetrakis-(4-carboxymethylphenyl)-21,23H porphine (TCMP) were synthesized with superior yields using microwave irradiation. Structures were confirmed by 1H-NMR, 13C-NMR, UV-Vis and FTIR spectroscopy. Various NMR experimental approaches (including 13C-NMR, DEPT, COSY, HMBC and HMQC) were used to completely elucidate some interesting aspects concerning the structure of the new porphyrin compounds.

The use of porphyrinic compounds in the field of theranostic nanomedicine, has increased substantially in the recent years due to their special features such as: long wavelength absorption and emission in the spectral region where the biological tissues absorb, a good photodynamic activity, photostability and low in vivo toxicity [1][2][3]. Despite significant advantages, due to the large  conjugate systems, porpyrins easily form aggregates, which have a significantly lower ability for localization at cellular level and consequently decrease the therapeutic effect. So, before pharmaceutical formulation, it is necessary the study of the spectral and aggregation properties of these compounds in membrane mimetic media, such as micelles, in order to determine the factors that modulate porphyrin−membrane interactions and that may resolve the aforementioned problems [4][5][6]. The present study included spectral evaluation of some amphiphilic porphyrins in TX-100/water and TX-100/cyclohexane micelles. The obtained results suggests for tested compounds the localization at the interface between the polyethylene oxide chains and the tertoctyl-phenyl etheric residue of the surfactant molecules. Regarding to spectral behavior of the studied porphyrins, the experimental results confirms fact that incorporation in micelles will facilitate a better delivery to the cellular target without determine significant change in their photophysical profile.