Supramolecular hydrogen

Fig. 31. Supramolecular (hydrogen-bonded) motifs of self-complementary molecules (196).

The rhombic (4,4) networks differ in the supramolecular interactions linking the cations and anions. For eleven (Table 2), alternating cations and anions are linked directly through hydrogen-bonded interactions. For two (Table 2) the supramolecular hydrogen-bonding assemblies incorporate protic solvents and for a single example (Table 2) there are no molecular interactions. 

Chino K, Ashiura M. Thermoreversihle cross-linking ruhher using supramolecular hydrogen-honding networks. Macromolecules 2001 34 9201-9204. 

Peng C-C, Abetz V. A simple pathway toward quantitative modification of polybutadiene a new approach to thermoreversible cross-linking rubber comprising supramolecular hydrogen-bonding networks. Macromolecules 2005 38 5575-5580. 

In an approach similar to that used for the supramolecular hydrogenation catalysts, supramolecular oxidation catalysts were also designed by connecting pyrazole-based... 

Local motions and segmental orientation in supramolecular hydrogen bond assemblies... 

Litvin, A.L., Valiyaveettil, S., Kaplan, D.L., and Mann, S. "Template-directed synthesis of aragonite under supramolecular hydrogen-bonded Langmuir monolayers". Adv. Mater. 9(2), 124-127 (1997). 

These results illustrate several important points. The mediating oxyl species are crucial for the transformation and seem to be stabilized by the fluorinated media. A supramolecular hydrogen bonding network can be anticipated as outlined in Scheme 24. Furthermore, BDD electrodes can not only be used for destructive... 

Quantum-field chemistry concept [5-9] treat transport of molecules inside the condensed phases of water as conduction through emptiness of two kinds (see Fig. 2). It is intramolecular emptiness restricted by grid intramolecular hydrogen (O-H—O) a-bonds inside supermolecule and, secondly, it is supramolecular emptiness lying between supermolecules confined by network of supramolecular hydrogen (O-H... O) (S-bonds and electrostatic y-bonds. 

The stable organic solid containing channels formed by the supramolecular hydrogen-bonded assembly of trithiocyanuric acid and 4,4 -bipyridyl can accommodate aromatic molecules such as benzene, toluene and /7-xylene. The apo-host is thermally stable up to 200 °C and exhibits shape selectivity with respect to the xylene isomers. The channels do not accommodate mesitylene. It would be interesting to carry out chemical reactions in these channels. 

Pedireddi, V. R., Chatterjee, S., Ranganathan, A. and Rao, C. N. R. (1998). A study of supramolecular hydrogen bonded complexes formed by aliphatic dicarboxylic acids with azaaromatic donors. Tetrahedron 54, 9457. 

Figure 4.9. Schematic representations of the crystal structures of the salts of enantiopure 5 with / -substiluted 1-arylethylamines in success, (a) Less soluble salts, in which the formation of a stable supramolecular hydrogen-bond sheet, the realization of efficient CII—ti interaction, and the close packing of the sheets are achieved, (b) More soluble salts, in which efficient CH n interaction is not realized and the close packing of the supramolecular sheets a stable supramolecular hydrogen-bond sheet is not formed, (c) More soluble salts, in which a stable supramolecular hydrogen-bond sheet is formed and the close packing of the supramolecular sheets is achieved, while efficient interaction is not realized.

Thus the crystallographic analyses of these less soluble diastereomeric salts revealed that the dominant interactions in the crystals are (1) the hydrogenbonding interaction, which constructs a consistent columnar supramolecular hydrogen-bond network, and (2) the CH tt interaction, which packs the columns tightly with each other. Thus the less soluble diastereomeric salts are efficiently stabilized by these two kinds of interactions. 

On the other hand, in the more soluble diastereomeric salts, there is also a columnar supramolecular hydrogen-bond network formed by hydrogen bonds between the carboxylates and the ammoniums, of which the pattern is quite similar to that of the corresponding less soluble diastereomeric salts... 

Foggasy and co-workers. In many cases, the hydrogen-bond chains form a supramolecular sheet. Thus it is strongly suggested that the chiral discrimination of racemic amines by enantiopure 9 mainly occurs through the formation of a supramolecular hydrogen-bond sheet (chain) of (9-H), which interact with the amine to discriminate its chirality. 

Of these crystal structures, 1-phenylethylammonium 2-phenylpropionate (NMACEP, PMACEP, Figure 4.38)115 and 2-phenylbutyrate (PEAPEA, PBUPEA)115,116 are the earliest examples reported by Brianso. The less soluble salt is the combination of the 5-acid with the R-amine (PMACEP and PEAPEA) in each case. The crystal structures of both pairs of the diastereomeric salts (less and more soluble salts) have been determined to show that these two systems have quite similar crystalline characteristics. In both less and more soluble salts a columnar hydrogen-bond network, formed by the carboxylate and ammonium groups, is commonly built around a two fold screw axis two molecules of the carboxylate part and two molecules of the ammonium part form a unit, which is piled up along a 2i-axis to form a supramolecular hydrogen-bond column. 

Thus there are plenty of reports on the resolutions of a wide variety of racemates with conventional resolving agents and on the crystal structures of the diastereomeric crystals of some combinations. These studies are rarely concerned with the correlation between the difference in stability of a pair of diastereomeric crystals and the efficiency of resolutions. However, the information about supramolecular hydrogen-bond systems obtained from these studies is very valuable for understanding such relationship in the resolutions of systematically selected racemates with a resolving agent. 

Paleos, C. M., Tsiourvas, D., Supramolecular hydrogen-bonded liquid crystals , Liquid Crystals 2001, 28, 1127-1161. 

A novel type of supramolecular hydrogen-bonded liquid-crystalline materials that are conceptually different from conventional H-bonded systems such... 

Fig. 8. Variable-temperature IR spectra of supramolecular hydrogen-bonded complex 5 (n = 4) consisting of 4-butoxybenzoic acid 2 and bipyridine 4 in the range 1500-1800 cm from 100-180 °C...

Fig. 18. Supramolecular hydrogen-bonded host-guest functional system...

Kinbara, K. Kobayashi, Y. Saigo, K. Chiral discrimination of 2-arylalkanoic acids by (lS,2R)-l-aminoindan-2-ol through the formation of a consistent columnar supramolecular hydrogen-bond network. J. Chem. Soc. Perkin Tran. 2000, 2, 111-119. 

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