Metal-ion-promoted electron transfer between tetrathiafulvalene and quinone units within a calix[4]arene framework and tuning through coordination of the neighboring crown ether with a sodium cation.

A new calix[4]arene 1 with tetrathiafulvalene (TTF), quinone, and crown ether units in the lower rim was designed and synthesized with the aim to investigate the possibility to tune the metal-ion promoted electron transfer by coordination of the crown ether unit with additional metal ions. Both absorption and electron spin resonance (ESR) spectroscopic studies clearly indicate that electron transfer occurs efficiently from TTF to the quinone units in the presence of Sc(3+)/Pb(2+)/Zn(2+). Moreover, the intramolecular electron transfer within 1 induced by Zn(2+) can be switched off by addition of Na(+) and further turned on by addition of either Sc(3+) or Pb(2+).