Multi-Responsive Eight-State Bis(acridinium-Zn(II) porphyrin) Receptor.

A multi-responsive receptor consisting of two (acridinium-Zn(II) porphyrin) conjugates has been designed. The binding constant between this receptor and a ditopic guest has been modulated (i) upon addition of nucleophiles converting acridinium moieties into the non-aromatic acridane derivatives and (ii) upon oxidation of the porphyrin units. A total of eight states has been probed for this receptor resulting from the cascade of the recognition and responsive events. Moreover, the acridinium/acridane conversion leads to a significant change of the photophysical properties, switching from electron to energy transfer processes. Interestingly, for the bis(acridinium-Zn(II) porphyrin) receptor, charge-transfer luminescence in the near-infrared has been observed.