Photophysical properties of multi-responsive Bis(acridinium/acridane-porphyrin) Molecular Switches

Most modern devices rely on multi-switchable systems for modular responses, which bring to different outputs. In this domain, a switchable bis(acridinium/acridane-porphyrin) conjugate, was designed to respond to different stimuli, namely electrons, nucleophiles and photons. The acridinium/acridane equilibrium is pH-dependent and significantly alters the photo- and electro-chemical properties.[1, 2] The coupling of N-substituted acridinium units to Zn-porphyrins brings to fluorescence quenching of both moieties by an ultrafast electron transfer process.[3] In the acridane-porphyrin system, instead, the porphyrin moiety retains its emission, since no electron transfer occurs between the two units. On the other hand, an efficient energy transfer process from the acridane unit to the porphyrin component has been observed upon acridane excitation. Interestingly, the switching between the acridinium/acridane forms allows the tuning of the photophysical properties of the arrays.