Malcolm A. Coffin

Functionalised Oligoenes with Unusual Topologies: Synthesis, Electrochemistry and Structural Studies on Redox-Active [3]- and [4]-Dendralenes

New [3]- and [4]-dendralenes bearing electron-donor 1,3-dithiole and ferrocene substituents have been synthesised. Compounds 8, 15 and 17 have been characterised by single-crystal X-ray diffraction. Two of the dithiole rings of 8 are conjugated (dihedral angle 9 degrees), while the third dithiole ring is almost orthogonal to this plane, and hence its pi-electron system is isolated. For the dendralene precursor molecule 15, the substituted cyclopentadienyl ring, two C=C bonds and fused dithiole and dithiine rings comprise an extended pi-conjugated system. In molecule 17 the potential conjugation path C(6)C(3) C(4)C(5)-C5Hs is distorted by an 8 degrees twist around the C(3)-C(4) bond and a 7 degrees twist around the C(5)-C(21) bond, and the delocalisation along the chain is insignificant. Solution electrochemical data demonstrate that the dendralenes are strong pi-electron donors, which give rise to dication, radical trication or tetracation species. Spectroelectrochemical studies on compounds 7 and 10 suggest that the radical species are situated within the linear 1,2-ethylenediylidene moieties and that a conformational change may occur at the dication redox stage. UV/Vis spectroscopic data are consistent with poor cross-conjugation in these systems.

Donor–π‐Acceptor Species Derived from Functionalised 1,3‐Dithiol‐2‐ylidene Anthracene Donor Units Exhibiting Photoinduced Electron Transfer Properties: Spectroscopic, Electrochemical, X‐Ray Crystallographic and Theoretical Studies

Steric interactions between the anthraquinoid core and the 1,3-dithiole and dicyanomethylene groups play a key role in determining the physical properties of system 1. The intramolecular charge transfer properties of this donor–π-acceptor species have been explored and cyclic voltammetric data, X-ray crystal structures and ab initio calculations are also reported.

Synthesis, X-ray crystal structure and multistage redox properties of a severely-distorted tetrathiafulvalene donor

Abstract Compound (2b) has been synthesised in one step from 2,3-dipentylanthraquinone. The X-ray crystal structure of (2b) reveals that the central quinonoid ring is distorted into a boat form; the di-, tri- and tetra-cations derived from (2b) are observed by cyclic voltammetry.

Synthesis and properties of new functionalized tetrathiafilvalene (ttf) pi-electron donors

The synthesis, solution electrochemistry, and X-ray crystal structures of a wide range of highly-functionalised TTF derivatives are presented.

1,3-DITHIOL-2-YLIDENE DERIVATIVES OF 1,3-INDANEDIONE

Abstract The synthesis is described of a series of mono-, bis-, and tris(1,3-dithiol-2-ylidene) derivatives7,9 and10 starting from 1,3-indanedione. Cyclic voltammetric data establish that the π-electron donor ability of these molecules increases in the sequence7 Mono-, bis-, and tris(1,3-dithiol-2-ylidene) derivatives of 1,3-indanedione have been synthesised, and their π-electron donor ability studied by cyclic voltammetry. The crystal structure of a complex (7a)2·TCNQ is reported. Download : Download full-size image

Redox-active, functionalised [3]- and [4]-dendralenes

A series of [3]- and [4]-dendralenes, functionalised with 1,3-dithiole groups, are synthesised and shown by cyclic voltammetry to undergo reversible multi-stage redox reactions to yield tri- and tetra-cation species, respectively; the X-ray crystal structure of a [3]-dendralene derivative is reported.

2,4,6-Tris(4,5-diisopropyl-1,3-dithiol-2-ylidene)cyclohexane-1,3,5-trione: synthesis, X-ray crystal structure and amphoteric redox properties of a highly delocalised heterocyclic π-system

The title compound 1 is synthesised by treatment of 1,3,5-trihydroxybenzene with 2-methylthio-4,5-di-n-propyl-1,3-dithiolium iodide in the presence of pyridine; the X-ray crystal structure of 1 reveals a highly delocalised π-system with strongly bonding intramolecular S ⋯ O interactions; four-stage, amphoteric redox behaviour is observed by cyclic voltammetry.