Proposed supramolecular structure

Cation-induced supramolecular formation of crown ether substituted phthalocya-nines can also be regarded as due to host-guest interactions. Fig. 10 shows the proposed structure for the K+- and Ca2+-induced dimer of metallophthalocya-nines fused with four 15-crown-5 units, which serves as a typical example. The formation of these cofacial dimers has been found to go through a two-step three-stage process. The earlier works have been briefly reviewed [93, 94], Recently, Jiang et al. have prepared a series of copper(II) phthalocyanines fused with one to four 15-crown-5 unit(s) [CuPc(15-C-5) ] (n = 1 1) by heating a solution of the double-decker complexes Eu(Pc)[Pc(15-C-5) ] (n = 1-4) with Cu(OAc)2 in... 

Cinnamoyl- 6-CD (6-CiO-/3-CD) was sparingly soluble in water, although most 6-substituted 6-CDs are soluble. However, 6-CiO-/3-CD was solubilized in water on the addition of adamantane carboxylic acid or p-iodoaniline which could be included in a 6-CD cavity. These results suggest that 6-CiO-/l-CD formed supramolecular polymers in the solid state, as shown in the proposed structure in Fig. 17. The X-ray powder pattern of 6-CiO-/l-CD was similar to that of the complex between p-CD and ethyl cinnamate, in which /3-CDs formed a layer structure. The crystal structure of 6-aminocinnamoyl-/3-CD (6-aminoCiO-/l-CD) is shown in Fig. 12 and we discussed the relationship between crystal packing and the substituent group in Sect. 2.8. 

Fig. 23 A proposed structure of a helical supramolecular polymer formed by 3-p- BocCiNH-a-CD in aqueous solution...

Fig. 24 Proposed structures of supramolecular polymer containing 3-AdHexNH-a-CD and 6-p- BocCiNH-/3-CD...

Fig. 6 a-c The synthesis of PEO-PHB-PEO triblock copolymer a, and the schematic illustrations of the proposed structures of a-CD-PEO-PHB-PEO inclusion complex b, and a-CD-PEO-PHB-PEO supramolecular hydrogel c [71]... 

Fig. 7 The synthesis route for PEO-grafted dextran a and the schematic illustration of proposed structure of supramolecular hydrogel by inclusion complexation between PEO-grafted dextran and a-CD b [77]...

Fig. 9 Proposed structure of the supramolecular hydrogel formed between a-CD and Pluronic copolymer in the presence of well-dispersed single-walled carbon nanotubes (SWNTs) [80]...

Fig. 12 a-c Proposed structures of supramolecular networks under different conditions, a PEO-PEI-dex-y-CD network is formed with a full double-strand complex at pH 10. b The Ml doublestand complex of PEO-PEI-dex-y-CD network is transformed to a partial double-stand complex at pH 4 owing to protonation of the PEI chains, c PEO-PEI-dex-a-CD networks do not form any double-strand complex at pH 10 [84]... 

Fig. 6 Structures of the non-mesogenic bis-pyridyl (2) and bis-benzoic acid (3) monomers studied by Griffin et al. [67] and the proposed structure of the main chain liquid crystalline supramolecular polymer (2-3) highlighting the length of supramolecular mesogen...

When supramolecular polymers are treated with bulky stopper groups, they may form poly[2]rotaxane daisy chains [45-53]. Harada et al. [31] treated 6-p-aminoCiO-a-CD (40 mM) with 2M excess 2,4,6-trinitrobenzenesulfonic acid sodium salt (TNBS) as bulky stoppers in aqueous solutions. The resulting precipitate was found to be mainly a cyclic trimer by H NMR and TOF mass spectra. After purification of the crude product, the 2D ROESY spectrum of the cyclic trimer shows cross-peaks between phenyl protons close to an amino group and secondary hydroxyl groups (0(2)H). A trinitrophenyl group is found at the secondary hydroxyl group side. A proposed structure of a cyclic trimer (cyclic daisy chain) is shown in Fig. 3.12. Kaneda et al. [38] reported the preparation of cyclic di[2]rota-xane fashion constructed tail-to-tail by azobenzene derivatives of permethylated a-CDs and showed its computer-generated supramolecular structures (Fig. 3.13). Easton et al. [39] also reported the preparation of cyclic di[2]rotaxane constructed by stilbene-appended a-CDs in tail-to-tail fashion (Fig. 3.14). Kaneda et al. [40]... 

Fig. 7.15 Proposed structure of the supramolecular structure formed by complexation of meso-tetraMs((4-pyridyl)porphyrinato)cobalt (CoPCpy) ) with [Ru(NH3)3(H20)3] on a graphite electrode...

Fig. 6 Proposed structures and gelatirai mechanism of snpramolecular hydrogels (a) nramal micellar hydrogel and (b) reverse micellar hydrogel. Stages 1 micellization of copolymer, 2 nonnal micellar hydrogel induced by supramolecular inclusion complexation, 3 reverse micellization of copolymer, and 4 reverse micellar hydrogelation. Reprinted with permission from [63]. Copyright (2010) Wiley-VCH...

Supramolecular structures formed during the crystallization of the melt under a tensile stress have already been described by Keller and Machin25. These authors have proposed a model for the formation of structures of the shish-kebab type according to which crystallization occurs in two stages in the first stage, the application of tensile stress leads to the extension of the molecules and the formation of a nucleus from ECC and the second stage involves epitaxial growth of folded-chain lamellae. 

In Chapter 5, Spector, Selinger, and Schnur describe such supramolecular architectures, which are formed in water from compounds derived from natural materials that have been altered in their ability to pack. Chirality plays an essential role in this area. However, there are the questions as to why these supramolecular structures are formed, the answers to which can improve approaches to control their architectures and dimensions. These authors evaluate several theories proposed to answer these fundamental questions. 

Figure 6 shows the proposed subunit assembly structure of the nicotinic acetylcholine receptor channel." The inner wall of the lower half part is surrounded by hydroxyl side chains from Ser and Thr, and by carboxylates or amides from Asp, Glu, and Gin at the mouth. Furthermore, a Lys residue seems to offer ion pairing with the carboxylate at the mouth. Considering the possibly similar stabilizing effect of ether and hydroxyl groups to cations, the proposed artificial supramolecular channel could be regarded as a good model of the acetylcholine receptor channel, which selects cations over anions, but does not discriminate between alkali metals. 

The prospective applications ofmolecular assemblies seem so wide that their limits are difficult to set. The sizes of electronic devices in the computer industry are close to their lower limits. One simply cannot fit many more electronic elements into a cell since the walls between the elements in the cell would become too thin to insulate them effectively. Thus further miniaturization of today s devices will soon be virtually impossible. Therefore, another approach from bottom up was proposed. It consists in the creation of electronic devices of the size of a single molecule or of a well-defined molecular aggregate. This is an enormous technological task and only the first steps in this direction have been taken. In the future, organic compounds and supramolecular complexes will serve as conductors, as well as semi- and superconductors, since they can be easily obtained with sufficient, controllable purity and their properties can be fine tuned by minor adjustments of their structures. For instance, the charge-transfer complex of tetrathiafulvalene 21 with tetramethylquinodimethane 22 exhibits room- temperature conductivity [30] close to that of metals. Therefore it could be called an organic metal. Several systems which could serve as molecular devices have been proposed. One example of such a system which can also act as a sensor consists of a basic solution of phenolophthalein dye 10b with P-cyciodextrin 11. The purple solution of the dye not only loses its colour upon the complexation but the colour comes back when the solution is heated [31]. 

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