Mixed-Valence Superstructure Assembled from a Mixed-Valence Host–Guest Complex

Herein, we report
an unprecedented mixed-valence crystal superstructure
that consists of a 2:1 host–guest complex [MV⊂​(CBPQT)2]2/3+ [MV = methyl viologen, CBPQT = cyclobis­(paraquat-p-phenylene)]. One electron is distributed statistically
between three [MV⊂​(CBPQT)2]•+ composed of a total of 15 viologen units. The mixed-valence state
is validated by single-crystal X-ray crystallography, which supports
an empirical formula of [MV⊂​(CBPQT)2]3·​(PF6)2 for the body-centered
cubic superstructure. Electron paramagnetic resonance provides further
evidence of electron delocalization. Quantum chemistry calculations
confirm the mixed-valence state in the crystal superstructure. Our
findings demonstrate that precise tuning of the redox states in host–guest
systems can lead to a promising supramolecular strategy for achieving
long-range electron delocalization in solid-state devices.