Figure 2.

Examples of frameworks displaying higher electronic delocalization. (a) Ligand-based delocalization through proximal S···S contacts in the [Zn₂(TTFTB)]_n framework where TTFTB = tetrathiafulvalenetetrabenzoate as shown at the top. (b) Mixed ligand–metal redox activity giving rise to charge delocalization throughout the backbone of ${[{({\text{NBu}}_4)}_2{\text{Fe}}_2^{\mathrm{III}}{(\text{dhbq})}_3]}_n,$ where dhbq represents dhbq²⁻ (2,5-dioxidobenzoquinone) and dhbq³⁻ (1,2-dioxido-4,5-semiquinone) in a mixed-valence state. (c) The H₂fan (3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone) analogue [(NBu₄)₂[Fe₂(fan)₃]]_n demonstrating electrochemical modulation of mixed-valence behaviour, probed by UV/Vis/NIR spectroelectrochemistry (bottom right). Reproduced with permission from the American Chemical Society [66–68]. (Online version in colour.)