title: Organic polyanionic high-spin molecular clusters: topological-symmetry controlled models for organic ferromagnetic metals.
abstract: Trianionic spin-quartet and tetraanionic spin-quintet molecular clusters derived from m-dibenzoylbenzene in solution were identified by CW-ESR/pulse-ESR based two-dimensional electron spin transient nutation spectroscopy, and their spin and clustering structures in the ground state were determined in terms of a D-tensor based phenomenological approach and DFT calculations. The molecular structures obtained semiempirically are supported by DFT-based quantum chemical calculations. The DFT calculations have been tested for a sodium ion bridged fluorenone-based cluster, [fluorenone(-)˙ {Na(+)(dme)(2)}](2), whose crystal structure was reported in the literature [H. Bock, H.-F. Herrmann, D. Fenske and H. Goesmann, Angew. Chem., Int. Ed. Engl., 1988, 27, 1067], reproducing the experimentally determined moelcular structure of the dimer cluster. It is suggested that both the quartet and quintet clusters in the 2-MTHF glass and solution form the cross-typed structures with the two m-dibenzoylbenzene moieties in cis-configuration. A dianionic spin-triplet m-dibenzoylbenzene derivative was detected for the first time and its charge and spin densities were studied by the quantum chemical calculations. The high-spin states of the open-shell entities under study were confirmed by X-band pulse-ESR based electron spin nutation spectroscopy in organic frozen glasses. The D values and other spin Hamiltonian parameters of all the polyanionic high-spin species were determined by the hybrid eigenfield spectral simulation for fine-structure ESR spectra. m-Dibenzoylbenzene provides pseudo-degenerate π-LUMOs arising from its topological symmetry of the π-electron network and its dianion in the triplet ground state is a prototypical model for topologically-controlled genuinely organic ferromagnetic metals.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. s-nakaza@sci.osaka-cu.ac.jp
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Nakazawa
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Sato
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shiomi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yano
authors.forename: Takamasa
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Maria Luisa T M B
authors.initials: ML
authors.lastname: Franco
authors.forename: Maria Celina R L R
authors.initials: MC
authors.lastname: Lazana
authors.forename: Maria Candida B L
authors.initials: MC
authors.lastname: Shohoji
authors.forename: Koichi
authors.initials: K
authors.lastname: Itoh
authors.forename: Takeji
authors.initials: T
authors.lastname: Takui