文摘
We describe a visible light-driven switchable [2]catenane, composed of a Ru(bpy)3p>2+p> tethered cyclobis(paraquat-p-phenylene) (CBPQTp>4+p>) ring that is interlocked mechanically with a macrocyclic polyether consisting of electron-rich 1,5-dioxynaphthalene (DNP) and electron-deficient 4,4鈥?bipyridinium (BIPYp>2+p>) units. In the oxidized state, the CBPQTp>4+p> ring encircles the DNP recognition site as a consequence of favorable donor鈥揳cceptor interactions. In the presence of an excess of triethanolamine (TEOA), visible light irradiation reduces the BIPYp>2+p> units to BIPYp>(鈥?)p> radical cations under the influence of the photosensitizer Ru(bpy)3p>2+p>, resulting in the movement of the CBPQTp>2(鈥?)p> ring from the DNP to the BIPYp>(鈥?)p> recognition site as a consequence of the formation of the more energetically favorable trisradical complex, BIPYp>(鈥?)p> 鈯?CBPQTp>2(鈥?)p>. Upon introducing O2 in the dark, the BIPYp>(鈥?)p> radical cations are oxidized back to BIPYp>2+p> dications, leading to the reinstatement of the CBPQTp>4+p> 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.
