Macrocycles within Macrocycles: Cyclen, Cyclam, and Their Transition Metal Complexes Encapsulated in Cucurbit[8]uril

Abstract

Reminiscent of Russian Matrioshka dolls, tetraazamacrocycles (1,4,7,10-tetraazacyclododecane (cyclen) and 1 , 4 , 8 , 11 - tetraazacyclotetradecane (cyclam)) and their transition metal complexes are encapsulated in the cavity of cucurbit[8]uril (CB[8]). The X-ray crystal structure of the [Cu(cyclen)] in CB[8] complex (see picture; copper: green, oxygen: red, nitrogen: blue, carbon: gray) reveals a five-coordinate Cu^II center in a square-pyramidal environment with a water molecule bound to the axial position.