Supramolecular Substitution

J. Santamaria, T. Martin, G. Hilmersson, S. L Craig, J. Rebek, Jr, Guest exchange in an encapsulation complex A supramolecular substitution reaction , Proc Natl. Acad. Sci. USA 1999, 96, 8344-8347. 

Zhao X, Wang XZ, Jiang XK, Chen YQ, Li ZT, Chen GJ. Hydrazide-based quadruply hydrogen-bonded heterodimers, structure, assembling selectivity, and supramolecular substitution. J Am Chem Soc 2003 125 15128-15139. 

The substituent effect on hydrogen bonds in the nucleobase pairs can be considered in three ways (1) substitution in the hydrogen bonding fragment (2) remote substitution, i.e., at positions not directly involved in hydrogen bonding and (3) supramolecular substitution (2006MI). 

Fig. 4.16 Representation of supramolecular substitution reaction between nonsymmetric oligomer 39 and symmetric oligomer 40. The H NMR spectra at different temperatures indicated that the complexation induced nonsymmetry. Reprinted with the permission from Ref. [35]. Copyright 2008 American Chemical Society...

Fig. 7.7 Top Supramolecular substitution of guest A by B in the softball. Bottom Two adjacent flaps open leaving six hydrogen bonds while the exchange reaction occurs...

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201). 

We do not discuss in detail the cases of tautomerism of heterocycles embedded in supramolecular structures, such as crown ethers, cryptands, and heterophanes, because such tautomerism is similar in most aspects to that displayed by the analogous monocyclic heterocycles. We concentrate here on modifications that can be induced by the macrocyclic cavity. Tire so-called proton-ionizable crown ethers have been discussed in several comprehensive reviews by Bradshaw et al. [90H665 96CSC(1)35 97ACR338, 97JIP221J. Tire compounds considered include tautomerizable compounds such as 4(5)-substituted imidazoles 1///4//-1,2,4-triazoles 3-hydroxy-pyridines and 4-pyridones. 

A unique feature of such DNA-directed self-assemblies is their site-selective immobilization, which makes it possible to construct well-defined nanostructures. On the other hand, the possibility of the introduction of a vast number of substitutes (like peptidic sequences, nucleoproteins, of hydrophobic hydrocarbon chains) to an adamantane core (adamantyl) makes such a process capable of designing steric colloidal and supramolecular conformations by setting hydrophobic/hydrophilic and other interactions. In addition, the rigidity of the adamantane structure can provide strength and rigidity to such self-assemblies [150]. 

In this review, CPOs constructed by covalent bonds are mainly focused on however, stable coordination bonds comparable to the stability of the covalent bonds have potential for future enhanced molecular design of novel CPOs. One representative is the bond between pyridine-type nitrogen and metal, which is widely used in supramolecular chemistry, that is, the cyclic supramolecular formation reaction between pyridine-substituted porphyrin and metal salts (Fig. 6d) [27,28]. Palladium salts are frequently used as the metal salts. From the viewpoint of the hard and soft acid and base theory (HSAB), this N-Pd coordination bond is a well-balanced combination, because the bonds between nitrogen and other group X metals, N-Ni and Ni-Pt coordination bonds, are too weak and too strong to obtain the desired CPOs, respectively. For the former, the supramolecular architectures tend to dissociate into pieces in the solution state, and for the latter. 

The silver(I) complexes with the tetrakis(methylthio)tetrathiafulvalene ligand have been reported, the nitrate salt presents a 3D structure with an unprecedented 4.16-net porous inorganic layer of silver nitrate,1160 the triflate salt presents a two interwoven polymeric chain structure.1161 The latter behaves as a semiconductor when doped with iodine. With a similar ligand, 2,5-bis-(5,5,-bis(methylthio)-l,3,-dithiol-2 -ylidene)-l,3,4,6-tetrathiapentalene, a 3D supramolecular network is constructed via coordination bonds and S"-S contacts. The iodine-doped compound is highly conductive.1162 (Methylthio)methyl-substituted calix[4]arenes have been used as silver-selective chemically modified field effect transistors and as potential extractants for Ag1.1163,1164... 

Abstract In this chapter, recent progress in the synthesis, crystal structures and physical properties of monomeric phthalocyanines (Pcs) is summarized and analysed. The strategies for synthesis and modification of Pcs include axial coordination of central metal ions, peripheral substitution of Pc rings and the ionization of Pcs. The crystal structures of various typical Pcs, especially the effects of different synthetic and modification strategies on the supramolecular assemblies of Pcs via %—% interactions between Pc rings, are discussed in detail. Finally, the UV-vis spectroscopic, conducting, magnetic and catalytic properties of some Pcs with crystal structures are presented briefly, and the correlations between various properties and the molecular structure discussed. 

As mentioned above (Section 2.1), inorganic and organic halides of TeIV are generally exhibiting halide-bridged supramolecular structures.1 3,6,7 Both Te X and X- X contacts are occurring, depending on the substitution patterns of compounds R4 TeX (n = 3, 2, 1). 

D.A.M. Egbe, B. Carbonnier, L. Ding, D. Miihlbacher, E. Birckner, T. Pakula, F.E. Karasz, and U.-W. Grummt, Supramolecular ordering, thermal behaviour, and photophysical, electrochemical, and electroluminescent properties of alkoxy-substituted yne-containing poly(phenylene-viny-lene)s, Macromolecules, 37 7451-7463, 2004. 

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