Unimolecular rectification of monolayers of CH3C(O)S-C14H28Q(+)-3CNQ(-) and CH3C(O)S-C16H32Q(+)-3CNQ(-) organized by self-assembly, Langmuir-Blodgett, and Langmuir-Schaefer techniques.

The advantage of "self-assembly" (strong covalent binding to substrates) was combined with the advantage of Langmuir-Blodgett (LB) or Langmuir-Schaefer (LS) transfer to a solid substrate (quantitative transfer of monolayers to the substrate). The electrical rectification (asymmetric conduction) by a monolayer of thioacetylalkylquinolinium tricyanoquinodimethanide was critically compared when these molecules had been transferred, by such competing techniques, onto gold electrodes, and then covered by a "cold gold" pad electrode. Unimolecular rectification was observed in the expected directions in the LB and LS monolayers. The Self-Assembled Monolayers (SAMs) were disordered; macroscopic measurements of rectification were unsuccessful for the SAMs, but successful for the down-stroke LB and LS monolayers, whose orientation and potential bonding to the Au surface should be identical to that of an ideal SAM.

Intramolecular charge-transfer interactions in pi-extended tetrathiafulvalene derivatives.

New electron-donor (D)-electron-acceptor (A) TTF architectures are presented in which two electron-donating 1,3-dithiole moieties are connected by a pi bridge to the weak electron-accepting quinoxaline moiety (D-pi-A compounds 9a and 9b and also two 1,3-dithiole-2-ylidene moieties are connected by a pi bridge to the electron-accepting thieno[3,4-b]quinoxaline bridge (D-pi-A-pi-D compounds 12a-c). There are through-bond intramolecular charge-transfer (ICT) interactions, predicted in theoretical calculations, and confirmed by UV-vis spectroscopy and cyclic voltammetry measurements. This work constitutes the first use of quinoxalines as electron-accepting moieties in D-pi-A compounds.

N,N-dimethylformamide-mediated sodium reduction of trans-3,3'-benzo[c]thienylidene-1,1'-dithione and trans-3,3'-benzo[c]selenonylidene-1,1'-dithione.

[reaction: see text] The synthesis of stable methylthio-capped biisothianaphthene and biisoselenophene derivatives has been achieved using DMF-mediated sodium reduction of cyclic thiocarbonyl compounds.

Synthesis of stable seleno[3,4-b]quinoxaline derivatives.

[reaction: see text]. The unstable seleno[2,3-b]quinoxoline was generated and functionalized in situ to give the stable dialdehyde and diester derivatives. The dicyano compound was made in several steps from biscyanomethyl selenide and was found to be very stable.

Synthesis of benzo[c]selenophene and derivatives via new routes.

[reaction: see text] Benzo[c]selenophene has been generated via facile bromination-dehydrobromination as well as oxidation of the 1,3-dihydrobenzo[c]selenophene. Benzo[c]selenophene thus generated has been lithiated in situ and treated with ClCOOEt to give the first functionalized derivative subject to X-ray crystallographic analysis.

Thiophene isosteres of 9,10-dithioanthraquinone.

[reaction: see text] The preparation of 1,3,5,7-tetramethyl-4,8-dihydrobenzo[1,2-c:4,5-c']dithiophene-4,8-dione and its conversion to the corresponding mono- and dithione are described.

Synthesis of the first 1,3-ditellurole-containing radialene-type TTF derivatives.

[reaction: see text] The first synthesis of dendralene-type TTF derivatives bearing a 1,3-ditellurole ring has been achieved. Preliminary electrochemical results are presented.

Generation of the first tellurium-containing diheteropentalene.

[reaction: see text] The known diester dibromomethylthiophene was converted to the tellurolo[3,4-c]thiphene, the first example of a diheteropentalene containing a tellurophene annelated across the 3,4-c position to thiophene. It is stable in solution and adds to DMAD across the 2,5-positions in tellurophene. The intermediate loses tellurium and collapses to a tetracarbomethoxy benzo[c]thiophene derivative.

Condensed thiophenes and selenophenes: thionyl chloride and selenium oxychloride as sulfur and selenium transfer reagents.

3,4-Cyanomethyl substituted thiophenes reacted with thionyl chloride in the presence of base to give dicyano substituted thieno(3,4-c)thiophenes. The use of selenium oxychloride furnished the corresponding cyano substituted seleno(3,4-c)thiophene. 1,2-Phenylenediacetonitriles gave the corresponding cyano substituted benzo(c)thiophenes and benzo(c)selenenophenes, respectively, upon reaction with thionyl chloride and selenium oxychloride in the presence of base.

Dendralene-type TTF vinylogs containing a 1,3-diselenole ring.

2-Diformylmethylene-1,3-diselenole was prepared and condensed with dithiolium phoshonium bromides and dithiolium phosphonates in the presence of base to give dendralene-type vinylogs of TTF bearing a 1,3-diselenole moiety. The electrochemistry of these dendrimers was studied. SEEPR measurements were also carried out. Calculations were carried out on the radical cations and correlated with the EPR values.

Synthesis of 3,4-ethylenedioxyselenophene (EDOS): a novel building block for electron-rich pi-conjugated polymers.

A multistep synthesis of the electron-rich 3,4-ethylenedioxyselenophene (EDOS) monomer is described. The electrochemical properties as well as the electropolymerization of EDOS are presented. [structure: see text]