The crystal structures and redox properties of p-benzoquinone (BQ)-fused crown-6 1 and bis-BQ-fused crown-6 2 were examined. The anion radicals of these BQ molecules were stabilized by addition of metal ions, through effective electrostatic interactions between the negatively charged BQ moiety and positively charged ion-capturing crown-6 unit. The electrostatic interactions and solvation energy played important roles in determining the magnitudes of anodic redox shifts in the reduction potentials. Regular π-stacking of BQ units and regular arrays of crown-6 units were observed in crystal 2, in which onedimensional π-electron columns were separated by ionic channels. The hydroquinone-fused crown-6 molecule 3 and a new BQ- and phenol-fused crown-6 derivative 4 were obtained as single crystals. The molecular conformations of crown-6 in crystal 3 and hydrated crystal 3·H2O were different from each other.
- Ion recognition
- Redox property