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 synthesized. In 1₆ a metal-induced 1,2,3-alternate-to-cone conformational change shortened the distance between these two groups and the electron-transfer efficiency was sharply increased. In 1₄ the electron-transfer efficiency was slightly increased in spite of a metal-induced rotation of the carbonyl groups which enlarges the distance between these two groups. These are novel responsive systems to control the electron-transfer efficiency between porphyrin and [60]fullerene.