Photophysical properties of supramolecular complexes made of bis(acridinium-porphyrin) tweezers and a tetra-pyridyl porphyrin guest

Metalloporphyrins, thanks to their rich photophysical behaviour and interesting electrochemical properties, have been widely studied as coordinating sites in supramolecular receptors. Interestingly, their redox potentials and photophysical properties can be tuned by modifying the lateral substituents, making them good candidates in the design of multicomponent systems where photoinduced electron transfer (eT) processes can be exploited.[1] In particular, it was recently showed that the association of porphyrins to N-acridinium chromophores in supramolecular conjugates brings to ultrafast eT processes from the porphyrin donor to the acridinium acceptor, which quench the fluorescence of both units.[2,3] Among recently designed acridinium-porphyrin receptors, bis(acridinium-porphyrin) tweezers (1 and 2, Figure 1) are of particular interest as multi-responsive arrays since they contain two Zn(II) porphyrin coordinating sites, and two acridinium ions as switching units.[3] Their complexation with a photoactive guest can lead to interesting photoinduced functions. In this context, we report here on the complexation processes involving the tweezers 1 and 2 and a meso-(5,10,15,20-tetra(4?-pyridyl)porphyrin, TPyP, (Figure 1) in different solvents; the observed photophysical behaviour will be discussed.