Herringbone crystal structure

Figure 6.2 Crystal structures of CB[ ], (a) Herringbone crystal structure of CB[5] and (b) one-dimensional (ID) channel structure of a complex between CB[6] and Rb cation.

Figure 6.3 Herringbone crystal structures of 6.1 from its acetonitrile solution.

In Section 4.5, we discuss the optical properties of clusters formed by sexi-thienyl molecules adopting the herringbone structure characteristic of their crystal structure [34]. The theoretical results arc compared to corresponding experimental measurements. 

In 1989, Krieg et al. [79] presented the crystal structure of the smectoge-nic frans-4-(as-4-cyano-cyclohexyl)cyclohexyl frans-4-n-heptylcyclohexano-ate (CCCHC). In contrast to all other substituents which are equatorially bonded in 1,4-positions to the cyclohexyl rings, the cyano group is axially attached. The molecules adopt a fully stretched conformation. Compound CCCHC has a tilted layer structure with a herringbone arrangement of layers. 

Vani and Vijayan [121] investigated the crystal structure of 7M-p-methoxy-benzylidene-p-phenyl-azoaniline (MBPAA). The two crystaUographically independent molecules are oriented antiparallel to each other. The packing of the molecules shows a herringbone arrangement. 

Recently, by crystal structure studies the number of different polymorphs of Copper Phthalocyanine Blue has been extended to nine, various of which are differing mainly in herringbone-type interaction [17]. 

Packing of the cyclodextrin molecules (a, p, p) within the crystal lattice of inclusion compounds (58,59) occurs in one of two modes, described as cage and channel structures (Fig. 7). In channel-type inclusions, cyclodextrin molecules are stacked on top of one another like coins in a roll producing endless channels in which guest molecules are embedded (Fig. 7a). In crystal structures of the cage type, the cavity of one cyclodextrin molecule is blocked off on both sides by neighboring cyclodextrin molecules packed crosswise in herringbone fashion (Fig. 7b), or in a motif reminiscent of bricks in a wall (Fig. 7c). 

There has been little work on the functionalization of higher acenes, owing to the poor stability and very low solubility of the non-benzannelated derivatives. A poorly refined crystal structure of unsubstituted hexacene has been reported (without atomic coordinates), implying that it too arranges in a herringbone motif analogous to the lower acenes [87]. 

Fig. 1 a-c Schematic representation of a channel type b cage herringbone type c cage brick type, crystal structures formed by crystalline cyclodextrin inclusion complexes. (Adopted from [18] with permission)... 

From some of these complexes, i.e. pyrrole/a-CD, EDT/a-CD, and EDT/p-CD, we were able to obtain single crystals that were studied by X-ray analysis. These show the herringbone fashioned cage-type crystal structure of pyrrole/a-CD, proving that it is a 1 1 complex with the pyrrole molecule located within the CD-cavity. The solid host-guest complexes are very stable under ambient conditions [21,22], After several weeks, the crystals remain unchanged while the unmodified monomers... 

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