Tris- complex supramolecular assembly

Other more complex supramolecular assemblies of disc-like architectures have also been reported. For example, self-assembly around a trifunctional core can yield columnar mesophases. This can be achieved by addition of appropriately long chain substituted benzoic acid derivatives (21) to a tris(imidazole) base (22) leading to the formation of a four component supramolecular disc (2I3-22) (Fig. 12a) which exhibits columnar mesophases. 

A second example of homochiral columns formed by discotics are the complexes of tetrazoles (59 and 60) with l,3,5-tris(4,5-dihydroimidazol-2-yl)benzene (61).74 Four molecules self-assemble to give a supramolecular disc and these discs subsequently form columns in nonpolar solvents. Chiral discs were obtained from the self-assembly of the chiral tetrazole (60) with 61. The chirality of the side chains was found to induce a bias in the helic-ity of the supramolecular assembly. Sergeants-and-soldiers measurements75 were performed for which chiral (60) and achiral (59) molecules were mixed. The experiments showed no amplification of chirality, thus revealing that in these systems chirality transfer from the side chains into the column is... 

As previously shown, /V, A-dimetylan i I i ne acts as an electron donor toward the electronically excited Ru(II) tris(dipirydyl) complex (Bock et al. 1979). Recently, this complex was juxtaposed to N,N -dimethy laniline via a salt bridge (Deng et al. 1997 Kirby et al. 1997 Roberts et al. 1997). Supramolecular assemblies have been prepared in which an electron may transfer from A.A-dimethylaniline to the electronically excited Ru(II) tris(dipyridyl) acceptor through the intervening amidinium-carboxylate salt bridge interface (Scheme 5-15). 

In the supramolecular assembly of the tetranuclear complex, 149, bis-(dicyclohexylammonium) tris(malonato)tetrakis(tributylstannate), 2[Cy2NH2] -[ Bu3SnOOCCH2COOSnBu3 Bu3SnOOCCH2COO 2]-2EtOH all four tin atoms are five-coordinate (trigonal bipyramidal) and the bis(tributyltin) unit bridges two mono(tributyltin)units. The structure also contains hydrogen-bonds to the cations and Sn <— O bonds from the terminal ethanol molecules [455],... 

A suspension obtained from the water-solnble anionic mew-tetrakis(4-carboxyphenyl)porphyrin and MWCNTs was nsed as an optical probe for DNA detection [242]. The same target was achieved very recently, constructing a supramolecular assembly with the water-soluble anionic 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin, covalently linked to MWCNTs and complexed with cyclodextrins (CD, either a-CD or P-CD) [243]. 

Stemming from their multifarious roles in natural processes, [metallo] porphyrins have found numerous applications in artificial systems aimed at mimicking important biological functions. Many different metalloporphyrins have been designed in order to accomplish specific tasks and, in particular, novel approaches have been used to assemble several porphyrins into a cluster. This ability to concentrate metalloporphyrins into a supramolecular assembly is of special relevance in that it takes us one step closer to constructing practical devices. This chapter will attempt to review the progress made in the assembly of porphyrin derivatives into supramolecular systems and will describe the aptitude of such assemblies to photosensitize particular reactions. The work described here is primarily concerned with trying to reproduce, under controlled conditions, some of the important features of photosynthetic reaction center complexes. 

Similarly, when a mixture of the two tris-bipyridine ligands 129 and 148 is allowed to react simultaneously with copper(l) and nickel(il) ions, only the double helicate 132 and the triple helicate 149 are formed (Figure 49). Thus, parallel operation of two programmed molecular systems leads to the clean self-assembly of two well-defined helical complexes from a mixture of their four components in a process involving the assembly of altogether 11 particles of four different types into two supramolecular species. 

Stabilization and crystallization of [Cr f/x-OI 0/0112)J(3j y>+ cations have been achieved by exploiting the supramolecular interactions with large anionic assemblies initially with mesitylene-2-sulfonate or its adduct with 18-crown-6,837-839 and subsequently with the adducts of calixarene sulfonates with N- or O-macrocycles.840,841 This approach, illustrated in Scheme 27, allowed the crystal structures of di-, tri- and tetrameric Cr111 complexes, (165)-(167),837,839-841 as well as that of a heteropolynuclear complex, [(H20)4Rh(/i-0H)2Cr(0H2)4]4+,838 to be determined. 

Another example of supramolecular columnar polymers formed by the combined use of hydrogen bonding and arene—arene interactions are the complexes of tetrazoles and l,3,5-tris(4,5-dihydroimidazol-2-yl)-benzene (53, Figure 28).231 Four molecules self-assemble to give a supramolecular disc-shaped molecule, which subsequently polymerizes into columns when in nonpolar solvents. Upon formation of a... 

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