Metal-induced conformational changes in calix[n]arenes can control the electron-transfer efficiency between porphyrin and [60]fullerene in an on-off manner

Calix[n]aryl esters (1(n):n=4 and 6) bearing a Zn(II)-porphyrin group as a fluorophore and a [60]fullerene group as a quencher on the lower rim were s ynthesized. In 1(6) a metal-induced 1,2,3-alternate-to-cone conformational change shortened the distance between these two groups and the electron-tra nsfer efficiency was sharply increased. In 1(4) the electron-transfer effic iency was slightly increased in spite of a metal-induced rotation of the ca rbonyl groups which enlarges the distance between these two groups. These a re novel responsive systems to control the electron-transfer efficiency bet ween porphyrin and [60]fullerene. (C) 1999 Elsevier Science Ltd. All rights reserved.