Herring-bone structure

The dominant intermolecular interactions in crystals of the smaller PAHs are between hydrogen atoms and carbon atoms, giving, as just described, a herring-bone structure. As the PAH becomes larger, the carbon-to-hydrogen ratio increases and intermolecular carbon-carbon interactions become relatively more important. The result is that the PAH molecules stack one above the other. These findings may be expressed by the potential energy expression - ... 

The crystal structures of the two systems are also very alike. Both are triclinic with comparable unit-cell parameters and with the "herring-bone" structure known from TTF-TCNQ /8/. The most pronounced crystallographic difference between the two systems is a rather elongated /6.1 %/ b-axis in TMTSF-DMTCNQ. This is to be expected because the b-direc-tion is across the width of the molecules where the additional methyl-groups tend to push the chains apart thereb. y probably reducing the interchain coupling. 

The results strongly indicate that a "peaked" conductivity vs temperature- curve is related to the "herring-bone" structure whereas the "four-nearest-neighbours" structure is characteristic for a solid with a less pronounced variation of the conductivity with temperature. 

Figure 7.14 Photograph of the microstructured falling film plates [52]. Insets show the structure in detail, (a) Reaction plate with rhomb structure, (b) Reaction plate with herring bone structure. Courtesy Fraunhofer ICT-IMM, Germany...

Meanwhile, investigations of wide domains have identified the causes of chevron, herring-bone structures. These result fi om interference between two modes with neighboring thresholds— the linear prechevron domains (deformation in the xz-plane) and the wide domains (deformation in the xy-plane). It has also proved possible to obtain such a herringbone structure by... 

Fujishima et al. found that SAMs prepared of azobenzene-terminated long chain alkanethiols on gold surfaces show a herring-bone structure in which the long axes of the azobenzene moieties are parallel to each other and the short axes of neighbouring molecules are perpendicular to each other (Fig. 27) [183,184], In contrast, phenylazonaphthol alkanethiol mono-layers are densely packed as a J-aggregate and well oriented with a tilt angle of 28° [185]. 

Cudzilo et al. and Huczko et al. noted that silicon and many silicides such as CaSi2 would yield nanofibrous mono-crystaUine SiC on reaction with PTFE [13,14]. Figure 15.10a,b shows the bulk of these fibres as obtained after purification steps. Figure 15.11a,b shows HRTEM of single SiC fibre with either stack or herring bone structure and amorphous SiO coating. 

Born in 1965 in Utrecht, the Netherlands, Marjolein van der Meulen received her Bachelors degree in mechanical engineering from the Massachusetts Institute of Technology in 1987. Thereafter, she received her MS (1989) and PhD (1993) from Stanford University. She spent three years as a biomedical engineer at the Rehabilitation R D Center of the Department of Veterans Affairs in Palo Alto, CA. In 1996, Marjolein joined the faculty of Cornell University as an Assistant Professor in the Sibley School of Mechanical and Aerospace Engineering. She is also an Assistant Scientist at the Hospital for Special Surgery, New York. She received a FIRST Award from the National Institutes of Health in 1995 and a Faculty Early Career Development Award from the National Science Foundation in 1999. Her scientific interests include skeletal mechanobiology and bone structural behavior. 

The resulting structures of FAPPO, given in Fig. 9, exhibit hydrogen bonding and a herring bone like orientation but form layers which are tilted differently towards each other. 

Plate 27. Large-scale image of the Au(lll)-22X-y/F recc truction. The Au(lll) surface reconstructs at room temperature to form a 22Xy/3 structure, which has a two-fold symmetry. On a large scale, three equivalent orientations for this reconstruction coexist on the surface. Furthermore, on an intermediate scale, a herring-bone pattern is formed. See Barth et al. (1990) for details. Original image be courtesy of J. V. Barth. 

Fig. 2.70 Structure of RcjB-type, (3, 3)ccpRe3 B , projected on (lOO)." Large circles are metal atoms and small ones are boron atoms. The figure shows on the left, the herring-bone pattern of <110>Nacb in the centre, the Reg empty octahedra and on the right, the RegB trigonal prisms. The arrows indicate the twin planes and the unit cell is indicated.

An x-ray crystallographic analysis of bcnzo[J,2,3- / 4,5,6-cV ]bis(thieno)[2,3-c]thiophene (61) demonstrated that the molecule is planar and symmetrical but has strained bond angles. The crystal structure comprises herring-bone type column stacking with intercolumnar heteroatom interactions. Compound (61) showed the same oxidation potential as perilene and, like perilene, formed an iodine complex with the relatively high electroconductivity of 0.11 S cm-1 <93BCJ2033>. 

Harata et al. [23] reported that the crystal structure of 2-0-[(S)-2-hydroxy-propyl]-y0-CD was solved by X-ray diffraction (Fig. 5). The molecules are arranged in a herring-bone fashion to form a cage-type packing structure. The hydroxypropyl group is inserted into the cavity of an adjacent molecule related by a two-fold screw axis. 

TTF-DETCNQ crystallizes in a triclinic lattice with each acceptor molecule surrounded by four donor molecules and vice versa /lo, 11/. In this respect, TTF-DETCNQ resembles TTF-TNAP /12/ and HMTSF-TCNQ /13/, which also have the "four-nearest-neighbours" structure and not the usual "herring-bone" with, only two nearest neighbours. 

The estimation of g then enables all the quantities in equation (43) to be evaluated, and hence allows a relation for a hypothetical, linear dextran g = 1) to be obtained. By this method, Wales and coworkers found g values which could not be reconciled with theoretical values calculated from the randomly branched model of Zimm and Stockmayer. This led to dextran s being assigned a herring-bone type of structure, that is, a linear backbone having branches of uniform length distributed uniformly along the chain. 

---