RESUMEN
An organic material composed of neutral free radicals based on the spirobiphenalenyl system exhibits a room temperature conductivity of 0.3 siemens per centimeter and a high-symmetry crystal structure. It displays the temperature-independent Pauli paramagnetism characteristic of a metal with a magnetic susceptibility that implies a density of states at the Fermi level of 15.5 states per electron volt per mole. Extended Hückel calculations indicate that the solid is a three-dimensional organic metal with a band width of approximately 0.5 electron volts. However, the compound shows activated conductivity (activation energy, 0.054 electron volts) and an optical energy gap of 0.34 electron volts. We argue that these apparently contradictory properties are best resolved in terms of the resonating valence-bond ground state originally suggested by Pauling, but with the modifications introduced by Anderson.
RESUMEN
We report the preparation, crystallization, and solid-state characterization of a benzyl-substituted spirobiphenalenyl radical. The crystal structure shows that the radical is monomeric in the solid state, with the molecules packed in an unusual one-dimensional (1-D) fashion that we refer to as a pi-step stack. This particular mode of 1-D stacking is forced on the lattice arrangement by the presence of the orthogonal phenalenyl units that were specifically incorporated to prevent the crystallization of low-dimensional structures. The structure shows that this strategy is effective, and neighboring molecules in the stack can only interact via the overlap of one pair of active (spin-bearing) carbon atoms per phenalenyl unit, leading to the pi-step structure in which the remaining four active carbon atoms per phenalenyl unit do not interact with nearest neighbor molecules. The magnetic susceptibility data in the temperature range 4-360 K may be fit to an antiferromagnetic Heisenberg S = 1/2 linear chain model with intrachain spin coupling J = -52.3 cm(-1). Despite the uniform stacking, the material has a room temperature conductivity of 1.4 x 10(-3) S/cm and is best described as a Mott insulator.
RESUMEN
The concept of Dewar benzene as a supramolecular protecting group for solid-state aryl-aryl interactions is reported. Photoisomerization of 1,4,5,6-tetramethyl-bicyclo[2.2.0]hexa-2,5-diene-2,3-dicarboxylic acid dimethyl ester (1) to the corresponding benzene isomer proceeds with rapid crystal formation. Herein this property is applied to the photolithographic patterning of crystal domains on a surface. [structure: see text]
RESUMEN
The new N5+ salt, N5+ SbF(6)(-), was prepared from N(2)F(+)SbF(6)(-) and HN(3) in anhydrous HF solution. The white solid is surprisingly stable, decomposing only at 70 degrees C, and is relatively insensitive to impact. Its vibrational spectrum exhibits all nine fundamentals with frequencies that are in excellent agreement with the theoretical calculations for a five-atomic V-shaped ion of C(2)(v)symmetry. The N5+ Sb(2)F(11)(-) salt was also prepared, and its crystal structure was determined. The geometry previously predicted for free gaseous N5+ from theoretical calculations was confirmed within experimental error. The Sb(2)F(11)(-) anions exhibit an unusual geometry with eclipsed SbF(4) groups due to interionic bridging with the N5+ cations. The N5+ cation is a powerful one-electron oxidizer. It readily oxidizes NO, NO(2), and Br(2) but fails to oxidize Cl(2), Xe, or O(2).
RESUMEN
[structure: see text] The synthesis of a rigid, tubular sexithiophene is reported. Close intermolecular Cl.Cl interactions play a significant role in defining the crystal structure.
