Tethered 1,4‐Benzoquinones and Their DCNQI Derivatives: Syntheses, Electronic Interactions, Redox Properties, Charge‐Transfer Complexes, and Copper Salts

Bisquinones 16–20, in which the quinoid moieties are tethered by 2-6 methylene units, have been synthesized via the bis(dimethoxybenzenes) 2, 6, 9, 14, and 15. Compounds 16–20 were transformed into the corresponding bis(DCNQIs) 21–25 using standard procedures. Interactions between the two quinoid units, which fade with the length of the tethering chain, have been observed by 13C-NMR spectroscopy, backed by calculated charge densities (Table 1) and by their cyclovoltammograms which indicate two independent two-step electron transfers. Similar results arise from ESR investigations of the bis(quinone) radical ions. All DCNQIs 21–25 form charge-transfer complexes with TTF and copper radical anion salts with reasonable powder conductivities. Since single crystals could not be grown, the structure of these materials remains unknown.