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

Abstract

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.

Through-Space Communication Effects on the Electrochemical Reduction of Partially Oxidized Pillar[5]arenes Containing Variable Numbers of Quinone Units

“…In 1993, Liberko et al investigated the electronic structure of helicenebisquinone anion radicals and concluded that they had delocalized electronic structures owing to the spatial proximity between the two quinone units. In 1998, Hünig and co-workers reported the electrochemical behavior of a series of bisquinones, in which the two quinoid groups are tethered by 2–6 methylenes. They found that the communication between the two quinone units faded quickly with the length of the tethering chain.…”