Edward M. Engler

Polymer‐modified electrodes: a new class of electrochromic materials

A new class of organic polymeric thin‐film electrochromic materials is described. We show that the new polymer‐modified electrodes change color reversibly in permanent thin‐film form without the electrodeposition characteristics of organic liquid state systems such as the viologens. The polymer films exhibit good switching speeds (τ⩽100 ms), possess intrinsic memory, and show no chemical degradation or adhesion loss in preliminary life tests (104 cycles). It is demonstrated that several important electrochromic parameters can be varied by chemical modification of the polymeric material.

Synthesis and properties of tetrathiafulvalene–metal bisdithiolene macromolecules

Reaction of tetrasodium tetrathiafulvalene-tetrathiolate with transition metal salts leads to the formation of tetrathiafulvalene-metal bisdithiolene oligomers which in the case of the nickel derivative possesses unusually high conductivity (ca. 30 Ω–1 cm–1).

Electrochemical reduction of carbon diselenide and preparation of 4,4′,5,5′-tetra(selenomethoxy)tetraselenafulvalene

Carbon diselenide has been electrochemically reduced and methylated to form 4,5-di(selenomethoxy)-1,3-diselenole-2-selone from which 4,4′,5,5′-tetra(selenomethoxy)tetraselenafulvalene was prepared.

‘Organic metals’: synthesis of dithiolylidenetetrathiapentalenones and their higher analogues

Reaction of the tetrathiapentalene-2,5-dione (1) and 4,5-dimethoxycarbonyl-1,3-dithiole-2-thione (2) with trimethylphosphite in refluxing benzene provides, along with the expected self-coupled products, the dithiolylidenetetrathiapentalenone (4; R = CO2Me) and its higher analogue (6; R = CO2Me).

‘Organic metals’. Isostructural tetrathia- and tetraselena-fulvalene salts of 2,5-diethyltetracyano-p-quinodimethane

Replacement of the sulphur atoms in the charge transfer salt tetrathiafulvalene (TTF)–2,5-diethyltetracyano-p-quinodimethane (DETCNQ) with selenium yields the isostructural and better conducting analogue tetraselenafulvalene (TSeF)–DETCNQ, in which the Peierls transition temperature is decreased.

Triselenathiafulvalenes: a novel sulphur–selenium interchange on trimethyl phosphite coupling of substituted 1,3-diselenole-2-thiones

Coupling using trimethyl phosphite of 4,5-dimethoxycarbonyl- and 4,5-ditrifluoromethyl-1,3-diselenole-2-thiones unexpectedly gave only tetramethoxycarbonyl- and tetratrifluoromethyl-triselenathiafulvalene respectively, while self-coupling of 4,5-dimethyl-1,3-diselenole-2-thione provided a mixture (85:15) of tetramethyltetraselenafulvalene and tetramethyltriselenathiafulvalene.

Enhanced axial–equatorial enthalpy differences in the methyl adamantanes

Analysis of the thermodynamic parameters for the isomerization with AlBr3 of 2-methyl- to 1-methyl-adamantane, ΔGI0(298)–2·47 ± 0·19 kcal mol–1, ΔHI0–3·37 ± 0·11 kcal mol–1, ΔSI0–3·0 ± 0·3 cal mol–1 deg–1, reveals an enhancement of the total axial methyl strain of 0·9 kcal mol–1 in the rigid adamantane system over that typical of cyclohexanes.

‘Organic metals’: acceptor stack doping in the charge-transfer salt tetraselenafulvalene–tetracyano-p-quinodimethane (TSeF–TCNQ)

Doping of methyltetracyano-p-quinodimethane into the ‘organic metal’ tetraselenafulvalene–tetracyano-p-quinodimethane obscures the phase transition at 28 K and increase the conductivity at 4 K by four orders of magnitude.

Synthesis of cis- and trans-diselenadithiafulvalene and its highly conducting charge-transfer salt with tetracyano-p-quinodimethane

cis- and trans-Diselenadithiafulvalene is synthesized in two steps, and its highly conducting, metallic-like charge-transfer salt with tetracyano-p-quinodimethane prepared.

Equilibration of biadamantane isomers

In agreement with molecular mechanics calculations, 2,2′-biadamantane (2) is more stable than 1,1′-biadamantane (1): (1)⇌(2), ΔGIo(298)=–0·51 ± 0·21 kcal mol–1, ΔHIo= 1·11 ± 0·12 kcal mol–1, and ΔSIo= 5·4 ± 0·3 cal deg–1 mol–1.