title: Regiochemical effects of furan substitution on the electronic properties and solid-state structure of partial fused-ring oligothiophenes.
abstract: Oligomers containing the new fused-ring heterocyclic conjugated building block thieno[3,2-b]furan were synthesized, and the effects associated with furan ring substitution into fused-ring oligothiophenes on the electronic properties and solid-state structure were assessed. A series of four-ring oligomers which vary in the degree of furan ring substitution and the regiochemistry of placement were synthesized via Stille cross-coupling and oxidative homocoupling strategies. The electronic properties of these oligomers were studied by UV-vis absorption and fluorescence spectroscopies. Substitution of furan rings at the terminal positions yields oligomers with a narrower HOMO-LUMO gap relative to the all-thiophene analogue 2,2'-bithieno[3,2-b]thiophene, and incorporation of furan rings at the interior positions results in oligomers with an increase in rigidity and a higher fluorescence quantum yield. Packing motifs of the oligomers were determined using single crystal X-ray diffraction. In contrast to the herringbone crystal packing observed for nonfused oligothiophenes, oligofurans, thiophene-furan hybrid oligomers, and the all-thiophene analogue 2,2'-bithieno[3,2-b]thiophene, all three regioisomers derived from the dimerization of thieno[3,2-b]furan arrange in a π-stacked packing motif in the solid state.
authors.affiliation: Department of Chemistry and the Macromolecular Science and Engineering Program, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Henssler
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Matzger
mesh_terms: D004583:Electrons; D005663:Furans / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005663:Furans; D013876:Thiophenes; C039281:furan