Energy and electron transfer processes in self-assembled cages with Zn trisporphyrin and free-base porphyrins or perylene bisimides

Non-covalent assemblies with multiporphyrin hosts represents an important challenge in relation to the mimicry of bacterial photosynthesis and the design of functional molecular materials. The self-assembly of a Zn trisporphyrin (1) induced by coordination with DABCO to form a stable 2:3 double-decker cage has been recently reported.1 This study aims to obtain similar self-assembled cages using photo or electro active guests as coordinating units and to study their photophysical behavior. The selected guests are a dipyridyl free-base porphyrin (2) and a dypiridyl perylene bisimide (3): both guests can axially coordinate two Zn porphyrins with their pyridine residues and offer the possibility of forming fully coordinated 2:3 trisporphyrin/host cages. The binding constants have been determined with UV-VIS and 1H NMR titrations and consequently the simulated speciation profiles have been derived for both cages. Photophysical investigations have been carried out in conditions where the cage is the major species. The molecular cages assembled with the photoactive components display interesting photoreactivity as energy and electron transfer.