Synthesis and Characterization of 6,13‐Diamino‐Substituted Pentacenes

A series of 6,13‐diamino‐substituted pentacenes 1 a – d has been prepared and characterized as a new class of pentacene derivatives with strong donor ability and enhanced solubility in common organic solvents. The spectroelectrochemical and DFT studies revealed that the two‐electron oxidation process was accompanied by the substantial structural change into a butterfly‐like conformation of the pentacene moiety. More importantly, the extent of deformation from the planar pentacene moiety in the dications of 6,13‐diaminopentacene is tunable by varying the N‐substituents.     

Supramolecular Assembly of Metal Chelates Based on Synthetic Bilayer Membranes

Synthetic bilayer membranes are two-dimensional arrays of am-phiphilic molecules. A large number of bilayer-forming am-phiphiles are designed by combinations of the structural elements (hydrophilic head, hydrophobic tail, connector, rigid segment, etc.). Metal chelate units have been incorporated into bilayer membranes as part of the bilayer component or as guest molecules. In the former example, a positively charged Cu(II)/polyamine complex and a Cu(II)/diketone unit are used as the hydrophilic head and rigid segment, respectively. The anisotropic orientation of these Cu(II) chelates is confirmed on the basis of the anisotropic ESR patterns observed for cast films of aqueous bilayer dispersions. Anionic planar Cu(II) complexes are incorporated noncovalently into cast films of ammonium bilayer membranes. These Cu(II) complexes are placed either horizontally or vertically, depending on the distribution of negative charges within each molecule. Strong antiferromagnetic interaction is observed when Cu(II) chelates are arranged two-dimensionally on bilayer membranes.     

Dynamic and microscopic X‐ray characterization of a compound chevron layer in electroclinic liquid crystals

The local layer structure of surface stabilized electroclinic liquid crystals has been analysed by time‐resolved synchrotron X‐ray microdiffraction. At a low applied electric field, the initial bookshelf structure starts to respond above a threshold voltage. With a low to medium applied field of triangular form, the layer structure transforms reversibly between the bookshelf (low field) and the compound chevron (high field), in which the vertical and horizontal chevrons alternate along the layer. When the horizontal chevron component appears, a stripe texture can be seen in an optical micrograph. With increasing field, the horizontal chevron becomes a dominant structure while the vertical chevron still remains. The layer spacing changes in correlation with the chevron angle during the field application. At high field, surface molecules partly rearrange, resulting in alignment deterioration at the interface. The layer response time for an a.c. square wave field is of the order of a few µs to ten µs, which is close to the optical response. The appearance of the compound chevron is discussed in conjunction with the anchoring effect.     

Spin-wave scattering from A γ-Fe47Mn53alloy

Spin waves in the antiferromagnetic alloy γ-Fe_0.5Mn_0.5 have been studied at $\text{295° K(}\text{T}\text{T}{}_{\mathrm{N}}\text{= 0.63)}$ by the inelastic neutron scattering technique. We observed an isotropic dispersion and obtained a value for the spin-wave velocity of 255 ± 30 meV Å (3.88 ± 0.50 × 10⁶ cm/sec), which is the order of the spin-wave velocity in Cr (a typical itinerant antiferromagnet). The energy gap at q = 0 was found to be 7.0 ± 0.5 meV. These results suggest the existence of a long-range spin ordering in the conduction electrons of this alloy.