Benzene-ring stack

Catenane synthesis can be also achieved by dynamic molecular association. Figure 3.27 shows an example of catenane preparation through the dynamic formation of a palladium (Pd) complex. Mixing the Pd complex with pyridine-type ligands in water induces the formation of both a monocyclic structure and an interlocked catenane. An equilibrium exists between these two structures, and the catenane structures are more favorable at higher concentrations. In the catenane structure, the benzene rings stack next to each other due to favorable... 

Some thiophenolate monolayers also have been investigated. Thiophenolate, C H S—, forms ordered monolayers on Ag(lll) with a (/7 X v, 88°)R40.9°, and benzene rings closely packed in face-to-face stacked columns (294). Benzylthiolate (295),/xpyridinethiolate (296), and (9-pyridinethiolate (296), also form ordered monolayers on Ag(lll), but with fewer close-packed aromatic rings. 

The result is explained by considering the stacking structure between the quinoline moiety and the benzene ring linked to the carboxylic acid, which gives the cavity size adequate for Li+. (Fig. 3) Several selective host molecules for Li+ such as [13]crown-4 18), [14]crown-4 19), [16]crown-4 20>, or noncyclic polyether amide derivatives 21) also possess trimethylene moiety, and this is an interesting finding from the point of view of molecular design of new host molecules for Li+. 

The theory had never been tested on a logical model system. Let us consider in detail one representative case, the superimposable stacking of the two benzene rings, one from each triplet diphenylcarbene molecule. These are considered to represent idealized modes of dimeric interaction of the aromatic ring parts of open-shell molecules in ordered molecular assemblies like crystals, liquid crystals and membranes. 

Fig. 20 Idealized stacking modes of two diphenylcarbene molecules. Two benzene rings, one each from the two carbenes, are always in a superimposable disposition.

All the results are summarized in Fig. 23 and serve as the first positive operational test for the McConnell theory. It is also noted that the orientational mode of stacking of spin-containing benzene rings can be useful in aligning spins parallel or antiparallel between high-spin aromatic molecules. 

The BIm-induced piled stack motif seems a true example of crystal engineering, since it is a relatively dependable structural assembly scaffold permitting tunability of the azole region of the molecule. Still, the piled stack formation seemed less tolerant of structure variation in the benzene ring of the BIm. Yoshioka and coworkers found that substitution on the BIm benzene ring often changed the chain contacts sufficiently to alter the exchange interactions from ID FM chains.197... 

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