Synthesis and characterization of novel dendritic compounds bearing a porphyrin core and cholic acid units using “click chemistry”

• Synthesis of new dendronized porphyrins containing cholic acid units.
• Emission at λ = 657 and 721 nm and formation of J-aggregates.
• Effect of the polarity, temperature, metallation and triazol on the aggregation.

Four novel dendritic molecules bearing a porphyrin core and peripheral cholic acid units (TPPh(Zn) Tetra-CA, TPPh(2H) Tetra-CA, TPPh(Zn) Octa-CA and TPPh(2H) Octa-CA) have been synthesized by the “click chemistry” approach, using azide-alkyne couplings. These compounds are fully characterized by 1H and 13C NMR spectroscopy and MALDI-TOF. The optical properties of the dendronized porphyrins are studied by absorption and fluorescence spectroscopy in different solvents, in order to study the amphiphilic properties of the cholic acid units in combination with the optical response of the porphyrin unit. After complexation with Zn, the metallated porphyrins (TPPh(Zn) tetra-CA and TPPh(Zn) octa-CA) tend to form J-aggregates in solvents of different polarity, whereas the free base porphyrins TPPh(2H) tetra-CA and TPPh(2H) octa-CA behaved differently. The aggregation phenomenon has been investigated by varying the polarity of the environment, temperature and metallation.