Redox-Responsive Host-Guest Chemistry of a Flexible Cage with Naphthalene Walls

Naphthocage, a naphthalene-based organic cage, reveals very strong binding (up to 10(10) M-1) to aromatic (di)cationic guests, i.e., the tetrathiafulvalene mono- and dication and methyl viologen. Intercalation of the guests between two naphthalene walls is mediated by C-H center dot center dot center dot O, C-H center dot center dot center dot pi, and cation center dot center dot center dot pi interactions. The guests can be switched into and out of the cage by redox processes with high binding selectivity. Oxidation of the flexible cage itself in the absence of a guest leads to a stable radical cation with the oxidized naphthalene intercalated between and stabilized by the other two. Encapsulated guest cations are released from the cavity upon cage oxidation, paving the way to future applications in redox-controlled guest release or novel stimuli-responsive materials.