Photocontrollable Supramolecular Self‐Assembly of a Porphyrin Derivative that Contains a Polyhedral Oligomeric Silsesquioxane (POSS)

Abstract

In this study, we have synthesized a new photosensitive organic–inorganic POSS‐containing hybrid porphyrin derivative (H2TPP−Azo−POSS), in which azobenzene was used as a bridge to conjugate the porphyrin and POSS, by using click chemistry. The self‐assembly behavior of H2TPP−Azo−POSS was studied at different concentrations in CHCl3 and in CHCl3/n‐hexane mixed solvent systems. Our results showed that the self‐assembled morphology of H2TPP−Azo−POSS could be tuned by varying the concentration and polarity of the solvent. Spherical micelles and linear nanowires could be obtained in CHCl3, whilst vesicles could be formed in CHCl3/n‐hexane mixtures with low polarities. The supramolecular self‐assembled morphologies of H2TPP−Azo−POSS demonstrated a light‐triggered transition behavior, whilst the size of the assembled aggregates decreased significantly under UV irradiation.

Polyhedral Oligomeric Silsesquioxanes (POSS)‐based Hybrid Materials: Molecular Design, Solution Self‐Assembly and Biomedical Applications

“…Among the various types of external stimulus, light irradiation was regarded as an ideal candidate, because it was clean, facile, and no additives were required. [ 110 ] In general, the construction of photoactive system could be achieved by introduction of special photo‐sensitive chromophores. Recent advances of azobenzene‐based polymeric system has gradually become popular candidate due to the unique properties including photo‐induced phase transition, optical nonlinearities, photophysical birefringence and dichroism.…”

Azides and Porphyrinoids: Synthetic Approaches and Applications. Part 1—Azides, Porphyrins and Corroles

“…The same research group, by following the LbL process and through a click approach, prepared other porphyrin-based molecular multilayer films (ITO-MP1-Zn) on indium tin oxide (ITO) electrodes for photovoltaic and photogalvanic devices [50]. Zhang and co-workers described the preparation of organic-inorganic hybrid porphyrin derivatives with a polyhedral oligomeric silsesquioxane (POSS) [51,52]. The authors followed two different synthetic approaches.…”

“…The authors found that different morphologies, such as core-shell spherical micelles and ordered square sheets, can be obtained depending on the polarity of the solvent or solvent mixtures used [51]. The same group prepared the photosensitive organic-inorganic porphyrin-POSS hybrid P69 with an azobenzene bridge ( Figure 7) [52]. The synthetic route involved the reaction of porphyrin derivative P67 with 4-azido-4´-hydroxyazobenzene affording the formation of the porphyrin-azobenzene derivative linked by 1,2,3-triazole rings (50% yield).…”

“…Through a substitution reaction with 3-bromoprop-1-yne in the presence of potassium carbonate, this compound afforded the corresponding alkyne derivative that was submitted to a second click chemistry reaction with POSS-N 3 to obtain the Zn(II) complex of P69-trans at a 51% yield. The treatment with HCl afforded the free-base derivative P69-trans in quantitative yield [52]. The azo bridge allowed the change from a trans to a cis configuration and, in such way, there is a significant reduction in the molecule size.…”

“…The supramolecular self-assembly of derivative P69-trans, as observed for compound P68, has a strong solvent dependence but additionally it also depends on the configuration. The possibility to modulate the structure by using light presents potentialities for applications in bio-imaging, drug release and catalysis [52].…”