title: Isostructural bisdithiazolyl and bisthiaselenazolyl radicals: trends in bandwidth and conductivity.
abstract: Reaction of N-alkylated pyridine-bridged bisdithiazolylium cations [1]+ (R1 =Me, Et; R2 =Ph) with selenium dioxide in acetic acid provides a one-step high-yield synthetic route to bisthiaselenazolylium cations [2]+ (R1 = Me, Et; R2 = Ph). The corresponding radicals 1 and 2 can be prepared by chemical or electrochemical reduction of the cations. Structural analysis of the radicals has been achieved by a combination of single-crystal and powder X-ray diffraction methods. While the two sulfur radicals 1 adopt different space groups (P3(1)21 for R1 = Me and P(-)1 for R1 = Et), the two selenium radicals 2 (space groups P3(1)21 for R1 = Me and P3(2)21 for R1 =Et) are isostructural with each other and also with 1 (R1 = Me, R2 = Ph). Variable-temperature magnetic measurements on all four compounds confirm that they are undimerized S = 1/2 systems, with varying degrees of weak intermolecular antiferromagnetic coupling. Variable-temperature electrical conductivity measurements on the two selenium radicals provide conductivities sigma(300 K) = 7.4 x 10-6 (R1 = Et) and 3.3 x 10-5 S cm-1 (R1 = Me), with activation energies, E(act), of 0.32 (R1 = Et) and 0.29 eV (R1 = Me). The differences in conductivity within the isostructural series is interpreted in terms of their relative solid-state bandwidths, as estimated from Extended Hückel band-structure calculations.
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Jaclyn L
authors.initials: JL
authors.lastname: Brusso
authors.forename: Shahab
authors.initials: S
authors.lastname: Derakhshan
authors.forename: Mikhail E
authors.initials: ME
authors.lastname: Itkis
authors.forename: Holger
authors.initials: H
authors.lastname: Kleinke
authors.forename: Robert C
authors.initials: RC
authors.lastname: Haddon
authors.forename: Richard T
authors.initials: RT
authors.lastname: Oakley
authors.forename: Robert W
authors.initials: RW
authors.lastname: Reed
authors.forename: John F
authors.initials: JF
authors.lastname: Richardson
authors.forename: Craig M
authors.initials: CM
authors.lastname: Robertson
authors.forename: Laurence K
authors.initials: LK
authors.lastname: Thompson