Two-electron Oxidation Wave Research Articles

Synthesis, structure and redox chemistry of 1,2-bis(ruthenocenyl)ethylene derivatives: a novel structural rearrangement to a (μ-η6∶η6-pentafulvadiene)diruthenium complex upon two-electron oxidation

Formylruthenocene, 1-formyl-1′,2′,3′,4′,5′-pentamethylruthenocene and 1-formyl-2,3,4,5-tetramethylruthenocene were treated with TiCl4–Zn in thf to afford the corresponding ethylene derivatives trans-1,2-bis(ruthenocenyl)ethylene, trans-1,2-bis(1′,2′,3′,4′,5′-pentamethylruthenocenyl)ethylene and trans-1,2-bis(2,3,4,5-tetramethylruthenocenyl)ethylene in excellent yields. Similarly, the dimethyl analogs were obtained from acetylruthenocene and 1-acetyl-1′,2′,3′,4′,5′-pentamethylruthenocene in good yields. Cyclic voltammograms of the ethylene complexes showed an irreversible two-electron oxidation wave at significantly lower potential than that of pentamethylruthenocene or ruthenocene. Two-electron chemical oxidation of these complexes with p-benzoquinone–BF3·OEt2 gave stable dicationic (µ-η6∶η6-pentafulvadiene)diruthenium complexes in moderate yields. The molecular structures of five complexes were determined by X-ray diffraction.

Novel Bis (1,3-Dithiole) Electron Donors by Oxidative Intramolecular Cyclization of 2,2′-Bis(1,4-Dithiafulven-6-yl)-3,3′-Bithienyls

2,2′-Bis(1,4-dithiafulven-6-yl)-3,3′-bithienyls 6 were prepared by using either a Wittig or a Wittig-Homer reaction. The cyclic voltammograms of 6 revealed that they undergo an intramolecular cyclization by electrochemical oxidation. Chemical oxidation of 6 with tris(4-bromophenyl)aminium hexachloroantimonate gave intramolecular cyclization products 16 as dication salts. The hexachloroantimonate ion was found to act as an oxidizing agent in the reaction. Chemical reduction of the dication salts with zinc afforded the corresponding neutral bis (1,3-dithiole) donors 7 in high yields. The cyclic voltammograms of 7 showed reversible one-stage two-electron oxidation waves, and the potentials are fairly low. A conductive TCNQ complex was formed from one of them. X-ray analyses of the neutral and dication states of the donor show that there is a large conformational change between them.

Synthesis and redox properties of largely π-extended p-quinodimethane analogues of tetrathiafulvalene

The highest known π-extended tetrathiafulvalene (TTF) analogues with a quinoid structure are reported; the cyclic voltammetry data reveal their strong donor character involving a two-electron oxidation wave to the dication when two dithiole rings are present in the molecule. A strong donor molecule bearing only a dithiole unit has been prepared from benz[ g]anthrone by a Wittig-Horner reaction and its electrochemical data reveal the presence of two one-electron oxidation waves to form the radical cation and dication; charge transfer complexes are formed in the presence of electron acceptors showing a mixed valence character.

Electrochemical oxidation of [1.1.1.1]pagodanes, bisseco-, seco- and dodecahedra(di)enes: stability of caged 4c/3e radical cations and 4c/2e dications

The anodic oxidation of variously functionalized[1.1.1.1]pagodanes A and bissecododecahedradienes B(π,π-distance, ca. 2.8 A) has been studied by cyclic voltammetry (CV). For nine out ot ten pagodanes A, independent of their functionalization and of the scan rate, an irreversible two-electron oxidation wave (Ep= 1.20–2.23 V) was observed in line with the sequence A→A˙+→B˙+→B2+(ECE) in which the chemical step C is very fast on the CV timescale. For seven of the corresponding valence isomeric dienes B, the first one-electron oxidation wave (B→B˙+), was found to be reversible(Eo′= 0.66–1.39 V) whilst the second one-electron oxidation wave (B˙+→B2+) was found to the irreversible (Ep= 1.20–1.80 V). The standard half-wave potentials allowed a thermodynamically meaningful estimate of the conjugative stabilization of the unusually persistent caged, non-classical 4c/3e radical cations B˙+(ΔEo′= 0.91 V for the parent diene B and the monoene reference) and of the destabilization by various functionalization patterns (0.40–0.73 V). For the secododecahedradienes D(π,π-distance ca. 2.85/3.2 A) and the dodecahedradienes E(π,π-distance ca. 3.5 A), only irreversible one-electron oxidation waves were recorded [Ep=(0.8)–1.46 V and (1.0)–1.39 V, respectively]. The degree of conjugative stabilization in the increasingly spherical, yet still non-classical 4c/3e radical cations D˙+ and E˙+ is approximated by ΔEp= 0.62 and 0.39 V, respectively.

A unique molecular donor containing two tetrathiafulvalene (TTF) units fused to 1,4 - ditellurin: Synthesis, X-ray structure and cyclic voltammetry

A new molecular donor composed of two TTF moieties fused to 1,4-ditellurin ( 3) has been synthesized and the structure has been characterized by X-ray diffraction. The cyclic voltammetry of both 3 and its methyl analogue 4 display two reversible two-electron oxidation waves.

ChemInform Abstract: Preparation and Properties of Tetrathio Derivatives of Quinodimethanes Fused to a 1,2,5‐Thiadiazole Unit and Related Heterocycles.

AbstractThe quinones (II), (V), or (VII) undergo Wittig‐Horner olefination with 2‐(dimethoxyphosphinyl)‐1,3‐benzodithiol (I) in the presence of butyllithium, forming the donor compounds (III), (IV), (VI), and (VIII).

Preparation and Properties of Tetrathio-derivatives of Quinodimethanes Fused to a 1,2,5-Thiadiazole Unit and Related Heterocycles

Abstract Wittig-Horner reaction of 2-dimethoxyphosphinyl-1,3-benzodithiole with 1,4-benzoquinones fused to a 1,2,5-thiadiazole unit and related heterocycles gave a new type of donors which show reversible two-electron oxidation waves and formed conductive complexes with iodine and DDQ.