title: Localization versus Delocalization in Chiral Single Component Conductors of Gold Bis(dithiolene) Complexes.
abstract: The first examples of chiral single component conductors are reported. Both (S,S) and (R,R) enantiomers of 5,6-dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) ligand have been used to prepare anionic metal bis(dithiolene) complexes formulated as ([(n-Bu)4N][M(dm-dddt)2] (M = Au, Ni), which are isostructural according to single crystal X-ray analysis. Single crystal transport measurements indicate semiconducting behavior for the anionic radical Ni complexes, with low room temperature conductivity values and high activation energies. Electrocrystallization experiments provided neutral [M(dm-dddt)2] (M = Au, Ni) complexes. The neutral radical gold compounds show intermolecular S···S interactions in the solid state giving rise to layers interconnected through weak C-H···S hydrogen bonds. The most peculiar structural feature concerns a dissymmetry between the two dithiolene moieties, while the nickel counterpart is symmetric. Single crystal resistivity measurements show thermally activated behavior for the open-shell gold complexes, with room temperature conductivity values of 0.02-0.04 S·cm(-1) and activation energies strongly influenced by hydrostatic pressure. A thorough theoretical study on nickel anion radical and gold neutral radical bis(dithiolene) complexes applied to the chiral complexes [M(dm-dddt)2] (M = Au, Ni(-)) and to a series of previously reported compounds addressed the issue of symmetry versus asymmetry from an electronic coupling perspective between the two dithiolene ligands. It results that neutral gold complexes with dithiolene ligands without extended delocalization are Class II mixed-valent compounds in the Robin and Day classification, presenting an inherent tendency toward asymmetric structures, which can be however modulated by the intermolecular organization in the solid state.
authors.affiliation: Université d'Angers , CNRS, Laboratoire Moltech-Anjou, UMR 6200, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers, France.
authors.forename: Diana G
authors.initials: DG
authors.lastname: Branzea
authors.affiliation: Université d'Angers , CNRS, Laboratoire Moltech-Anjou, UMR 6200, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers, France.
authors.forename: Flavia
authors.initials: F
authors.lastname: Pop
authors.affiliation: Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Sud, Université Paris-Saclay , Orsay 91405, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Auban-Senzier
authors.affiliation: CNRS, CRPP, UPR 8641 , Pessac F-33600, France.|Univ. Bordeaux, CRPP, UPR 8641 , Pessac F-33600, France.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clérac
authors.affiliation: Departament de Ciència de Materials i Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona , Martí i Franquès 1, Barcelona 08028, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Alemany
authors.affiliation: Institut de Ciència de Materials de Barcelona (CSIC) , Campus de la UAB, Bellaterra E-08193, Spain.
authors.forename: Enric
authors.initials: E
authors.lastname: Canadell
authors.affiliation: Université d'Angers , CNRS, Laboratoire Moltech-Anjou, UMR 6200, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers, France.
authors.forename: Narcis
authors.initials: N
authors.lastname: Avarvari