Hydrogen-bonded nanostructures

Jolliffe, K. A. Timmerman, R Reinhoudt, D. N. Noncovalent assembly of a fifteen-component hydrogen-bonded nanostructure. Angew. Chem. Int. Ed. 

The multicomponent nature of hydrogen-bonded nanostructures based on rosette motifs as well as the multiple sites available for further chemical modifications at building blocks make these structures a very interesting candidates for the precise spatial arrangement of functional diversity onto solid supports. 

The synthesis of cahx[4]arene dimelamines with different functionalities and their self-assembly with barbituric and cyanuric acid to hydrogen-bonded nanostructures have been published <05OBC3727> Unique ionophores of penta-crown ethers have been prepared by the reaction of l,3,5-triacryloylhexahydro-l,3,5-triazine (TAHTA) with diaza 18-crown-6 followed by Michael addition, and their binding capabilities towards alkali metal cations studied <05SL2257>. New silver complexes of polydentate ligands including a derivative of pyrazol-l-yl-l,3,5-triazine have been reported <05EJ14370>. 

Russell. V.A. Ward. M.D. Molecular crystals with dimensionally controlled hydrogen-bonded nanostructures. Chem. Mater. 1996. 8. 1654. 

For the assembly of triblock copolymers into nanostructures see Ref. 38 also see, for instance, the recently described self-assembly of rodUke hydrogen-bonded nanostructures, Ref. 39. t For the interaction between a molecule and a modified nanocrystalUne solid bearing a complementary recognition group, see, for instance. Ref. 44. 

Figure 5.10 Schematic overview of self-assembly process of high-axial-ratio nanostructures using bolaamphiphilic monomers. Arrows indicate hydrogen bond functionalities. Reprinted from Ref. 53 with permission of Wiley-VCH.

Figure 5.22 Cu UPD on a Au/mica substrate modified by a hybrid nanostructure consisting of a hydrogen-bonded network and a thiol SAM. (a) Cartoon ofthe hybrid structure and molecular structures of the components. The hydrogen-bonded network is composed of 1,3,5-triazine-2,4,6-triamine (melamine, triangles) and perylene-3,4,9,10-tetracarboxylic di-imide (PTCDI, rectangles) that interact via a triple hydrogen bond (dotted lines). Pores ofthe...

Nanostructures are, literally, facts of life in biology. Proteins, viruses, and bacteria are nanosized, three-dimensional structures which have been self assembled from smaller subunits. Although individual atoms in the subunits (polypeptides, for example) are covalently linked, assembly of the subunits is maintained by non-covalent (van der Waals, hydrogen-bonding, electrostatic, and hydrophobic) interactions. 

The photoelectrochemistry at atomically well-defined semiconductor surfaces is one of the current topics related to the nanostructuring of the semiconductor surfaces. Most studies have been made on silicon (Si) surfaces, and it is now well established that hydrogen fluoride (HF)-etched Si surfaces are terminated mainly with Si-hydrogen bonds (SiH , n = 1, 2, or 3)14-171 and that, for Si (111), successive etching with 40% ammonium fluoride (NH4F) produces atomically flat Si(l 11) surfaces, terminated mainly with monohydride (= Si-H).18-221 Alkali etching under negatively applied biases also produces similar atomically flat Si (111) surfaces.231... 

In biological recognition phenomena, protein-protein interactions are of primary importance. In an attempt to mimic these processes, LaBrenz and Kelly [51] synthesized the peptidic host 64. In this receptor, the dibenzofuran template separates the two peptide units by roughly 10 A and allows for the complexation of a guest peptide (65), as depicted in Fig. 21. The complex first forms a three-stranded, antiparallel /J-sheet that is stabilized by hydrogen bonds, electrostatic interactions, and aromatic-aromatic interactions between the dibenzofuran and the benzamide moieties. This complex can further self associate to form more complex structures. This example shows that structurally defined peptide nanostructures can interfere with biological recognition processes and potentially have therapeutic applications. 

The lastest development is the completely reversible formation of the nanostructures comprising 8 different rosette layers (27 different components) that are held together by 144 cooperative hydrogen bonds. Regarding their size (—5.5 x 3.1 x 2.7 nm) and their molecular weight ( 20 kDa), these nanostructures are comparable to small proteins (Figure 4.4).14... 

The formation of synthetic hydrogen-bonded structures is typically achieved under thermodynamic control. Therefore, product formation is usually quantitative because erroneous structures can dissociate and recombine to give the correct assembly. However, it is expected that a large increase in the number of hydrogen bonds will lead to a kinetic control in the self-assembly process limiting the use of noncovalent synthesis of nanostructures. 

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