We describe a visible light-driven switchable catenane, composed of a Ru(bpy)32+ tethered cyclobis(paraquat-p-phenylene) (CBPQT4+) ring that is interlocked mechanically with a macrocyclic polyether consisting of electron-rich 1,5-dioxynaphthalene (DNP) and electron-deficient 4,4′-bipyridinium (BIPY2+) units. In the oxidized state, the CBPQT4+ ring encircles the DNP recognition site as a consequence of favorable donor-acceptor interactions. In the presence of an excess of triethanolamine (TEOA), visible light irradiation reduces the BIPY2+ units to BIPY(•+) radical cations under the influence of the photosensitizer Ru(bpy)32+, resulting in the movement of the CBPQT2(•+) ring from the DNP to the BIPY(•+) recognition site as a consequence of the formation of the more energetically favorable trisradical complex, BIPY(•+) CBPQT2(•+). Upon introducing O2 in the dark, the BIPY(•+) radical cations are oxidized back to BIPY2+ dications, leading to the reinstatement of the CBPQT4+ ring encircled around the DNP recognition site. Employing this strategy of redox control, we have demonstrated a prototypical molecular switch that can be manipulated photochemically and chemically by sequential reduction and oxidation.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry