Edward M. Engler, Vishnu V. Patel
Journal of Organic Chemistry
Two synthetic approaches for modifying hexamethylenetetraheterofulvalene donors are described for the purpose of perturbing in a systematic way the interesting solid state properties of the TCNQ salts of the parent systems. The first approach consists of a steric modification in which a methyl group is introduced into the outer five-membered rings of the parent molecules to give di(3-methylcyclopenteno)-[1,2-b;1',2'-h]-1,4,5,8-tetrathiafulvalene (6a, α-MeHMTTF), di(4-methylcyclopenteno)-[1,2-b; 1' 2'-h]-l,4,5,8-tetrathiafulvalene (6b, β-MeHMTTF), di(4-methylcyclopenteno)-[l,2-b;1',2'-h]-1,5- (and/or 1,8-)diselena-4,8- (and/or 4,5-)dithiafulvalene (11, β-MeHMDSeDTF) and di(4-methylcyclopenteno)-[1,2-b-1',2'-h]-1,4,5,8-tetraselenafulvalene (9, β-MeHMTSeF). Donor 6b forms both insulating and highly conducting (σRT=80/ohm·cm, single crystal) charge transfer complexes with TCNQ, whereas the selenium-containing analogues, 11 and 9, form only insulating TCNQ compounds. Donor 6a gives a moderately conducting TCNQ complex (σRT=10-1/ohm·cm). The second type of modification involves an electronic perturbation in which the outer five-membered alkyl rings are replaced with fused thiophene derivatives to give cis-/trans-dithieno[2,3-b;2',3'-h]-1,4,5,8-tetrathiafulvalene (26, α-TTTF) and the separable cis and trans isomers of di(4,5-dihydrothieno)-[2,3-b;2',3'-h]-l,4,5,8-tetrathiafulvalene (24a, cis-, and 24b, trans-α-DTTTF). Both 24a and 24b form highly conducting TCNQ complexes (σRT ≈ 20/ohm·cm, powder) whereas 26 forms a semiconducting TCNQ complex. © 1978, American Chemical Society. All rights reserved.
Edward M. Engler, Vishnu V. Patel
Journal of Organic Chemistry
Edward M. Engler, Vishnu V. Patel, et al.
Journal of the Chemical Society, Chemical Communications
Edward M. Engler, Vishnu V. Patel
Journal of the Chemical Society, Chemical Communications
Edward M. Engler, Vishnu V. Patel, et al.
Tetrahedron Letters