Photocontrol over Cooperative Porphyrin Self-Assembly with Phenylazopyridine Ligands

摘要

The use of external stimuli to control the self-assembly of multicomponent systems has great potential to interconvert the system's morphology and functions. In this area, an interesting field is the dynamic photoregulation of artificial self-assembling systems that comprises archetypical elements for biological mechanical activities, such as cell migration and mass transfer. In biological systems, the interconversion of small molecules as secondary components, such as GTP and GDP, brings about the dynamic character of supramolecular structures, for instance the dynamic instability of microtubules. A major challenge in chemistry is to regulate artificial supramolecular structures in a similar way, in which multiple components interact with each other and dynamically alter the structures and functions of the system. Similar to biological systems, the dynamic response will be significantly enhanced in cooperative mechanisms in which self-assembly features distinctive nucleation and elongation events. In contrast, most artificial systems show non-cooperative or isodesmic aggregation behavior. So far, many intriguing photostimulated self-assembly approaches have been published; in these approaches photochemical switching is performed on the supramolecular building block itself. We now describe a successful example of the photoregulation of the cooperative self-assembly of zinc porphyrins by photo-chromic auxiliaries, which are based on phenylazopyridine axial ligands.