Partial oxidation of the pillar[5]­arene macrocycle with Fe­(III) leads to the isolation of a fibrous purple solid with high porosity. Experimental and computational data indicate that the solid material is primarily composed of macrocycles in which two of the hydroquinone units have been oxidized to benzoquinone units. Self-assembly takes place through the formation of multiple quinhydrone charge-transfer complexes between hydroquinone and benzoquinone units on adjacent macrocycles, providing a rare example of self-assembly based on a pentagonal molecular symmetry.