title: Semiquinone-bridged bisdithiazolyl radicals as neutral radical conductors.
abstract: Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna2(1), revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-temperature conductivity measurements on 3a and 3a·MeCN indicated high values of σ(300 K) (>10(-3) S cm(-1)) with correspondingly low thermal activation energies E(act), reaching 0.11 eV in the case of 3a·MeCN. Overall, the strong performance of these materials as f = ½ conductors is attributed to a combination of low U and large W. Variable-temperature magnetic susceptibility measurements were performed on both 3a and 3a·MeCN. The unsolvated material 3a orders as a spin-canted antiferromagnet at 8 K, with a canting angle φ = 0.14° and a coercive field H(c) = 80 Oe at 2 K.
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
authors.forename: Aaron
authors.initials: A
authors.lastname: Mailman
authors.forename: Kristina
authors.initials: K
authors.lastname: Lekin
authors.forename: Abdeljalil
authors.initials: A
authors.lastname: Assoud
authors.forename: Craig M
authors.initials: CM
authors.lastname: Robertson
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Noll
authors.forename: Charles F
authors.initials: CF
authors.lastname: Campana
authors.forename: Judith A K
authors.initials: JA
authors.lastname: Howard
authors.forename: Paul A
authors.initials: PA
authors.lastname: Dube
authors.forename: Richard T
authors.initials: RT
authors.lastname: Oakley
mesh_terms: D016227:Benzoquinones / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004553:Electric Conductivity; D008280:Magnetics; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D013844:Thiazoles / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D016227:Benzoquinones; D013844:Thiazoles; C025232:semiquinone radicals