Photophysical Characterization of Bis(Acridinium-Porphyrin) and Bis(Acridane-Porphyrin) Receptors

Simple systems for information transmission can be obtained with chemo-, electro- or photo-triggered molecular switches. In this perspective, N-substituted acridinium units are particularly intriguing as building blocks in the design of supramolecular entities since they act as multiresponsive components by modifying their chemical and electronic structure upon chemical or redox orthogonal stimuli [1]. Indeed, it is possible to switch between acridinium and acridane units by means of chemical and photochemical stimuli. Besides, metallo-porphyrins are interesting components to be included in the design of molecular switches, since they can act as versatile supramolecular receptors thanks to their extended aromatic p-system able to interact with electron poor guest molecules. It has been reported that in some host-guest systems, where acridinium units and porphyrins are involved, a fast photoinduced electron transfer process between the porphyrin host and the acridinium guest takes place [2,3]. Two tweezer-type arrays consisting of a bis(porphyrin-acridinium) and a bis(porphyrin-acridane) conjugates, where the acridinium/acridane units are connected by a flexible linker (Figure 1), were conceived to associate the binding properties of the two porphyrins to the large stimuli responsiveness of the two acridium units. Herein, we report on the photophysical properties of these supramolecular tweezers and on the photoinduced processes occurring among their components.