title: Multiple reduction of 2,5-bis(borolyl)thiophene: isolation of a negative bipolaron by comproportionation.
abstract: The 2,5-bis(borolyl)thiophene 2, a conjugated acceptor-π-acceptor system, can be reduced to the monoradical anion [2](.-) , the dianion [2](2-) , and the tetraanion [2](4-) . The dianion [2](2-) was also prepared by a comproportionation reaction and features an absorption maximum in the near-IR region (λmax =800 nm), which is characteristic of a bipolaron with a quinoidal structure.
authors.affiliation: Institut für Chemie und Pharmazie, Julius-Maximilians-Universität Würzburg (Germany). h.braunschweig@mail.uni-wuerzburg.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.forename: Vladimir
authors.initials: V
authors.lastname: Dyakonov
authors.forename: Bernd
authors.initials: B
authors.lastname: Engels
authors.forename: Zarah
authors.initials: Z
authors.lastname: Falk
authors.forename: Christian
authors.initials: C
authors.lastname: Hörl
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Klein
authors.forename: Thomas
authors.initials: T
authors.lastname: Kramer
authors.forename: Hannes
authors.initials: H
authors.lastname: Kraus
authors.forename: Ivo
authors.initials: I
authors.lastname: Krummenacher
authors.forename: Christoph
authors.initials: C
authors.lastname: Lambert
authors.forename: Christof
authors.initials: C
authors.lastname: Walter
mesh_terms: D000838:Anions / Q000737:chemistry; D001896:Boron Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D010084:Oxidation-Reduction; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D000838:Anions; D001896:Boron Compounds; D013876:Thiophenes
keywords: bipolarons; boroles; conjugation; quinoidal structures; thiophene