Synthesis of porphyrin glycoconjugates bearing thiourea, thiocarbamate and carbamate connecting groups: Influence of the linker on chemical and photophysical properties

• Synthesis of six new porphyrin conjugates, including three glycoporphyrins.
• Chemical characterization and linker conformation studies.
• Singlet oxygen production, photostability and self-aggregation studies.
• Carbamate derivates have proven to be good candidates for PDT studies.

In the present work, we have synthesized new porphyrin conjugates bearing thiourea, thiocarbamate and carbamate linkers using conventional and ultrasound-assisted methods. These molecules were synthesized by addition reactions using isothiocyanate derivates and amino- or hydroxyl-functionalized meso-tetra(aryl)porphyrins to give porphyrin analogs linked to glycosyl or benzyl moieties. Glycoporphyrin derivates could be obtained with better yields than their respective benzyl analogs. Thiourea and carbamate glycoporphyrins were also successfully synthesized through an ultrasound protocol with a remarkable decreasing of the reaction time. By NMR experiments we were able to evaluated the linker conformations which showed a preferred Z,Z conformation for the thiourea and carbamate derivatives. In addition, porphyrins were evaluated in terms of their UV–Vis spectra, singlet oxygen production, photostability and aggregation properties. Correlations between the linker type and the corresponding photophysical properties were observed. Carbamate porphyrins seem to be the most promising photosensitizers among the studied molecules due to their high singlet oxygen production, photostability and absence of self-assembling behavior in aqueous media.

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