Hydrogen bonding self-assembled molecules, chirality

Finally, we mention a remarkable example of lateral resolution reported for supramolecular nanostructures on hopg [96]. Held together by 72 hydrogen bonds, the molecular nanostructure is formed from three melamine-substituted calix[4]arene units and twelve 5,5-diethylbarbiturate molecules (Fig. 31a). The nanostructure, basically a stack of four rosettes, has chiral symmetry. With its components all being achiral, both enantiomers are formed upon self-assembly in solution. Deposition of the tetrarosettes on hopg leaves this nanostructure intact and allows surface self-assembly. AFM studies revealed close-packed 2D lattices formed by the tetrarosettes on hopg... 

Chirality may also be found in assemblies of nonchiral molecules held together by noncovalent forces such as hydrogen bonds or metal coordination. Such bonds are reversible errors in connecting single parts of such an assembly may be corrected, which helps in the construction of larger structures by self-assembly . 

MacGillivray and Atwood have demonstrated the ability of six resocin[4]arenes to self-assemble to give a very large molecular capsule of octahedral symmetry.67 Specifically, six molecules of tetramethylresorcin[4]arene assembled with eight water molecules via 60 hydrogen bonds to form a capsule, approximately 2.5 nm in diameter, that accommodated multiple solvent molecules as guests. The assembly was chiral, possessing a structure that conformed to an Archimedean solid known as a... 

Subsequent self-assembly with L54 through hydrogen bonding leads to three t)rpes of chiral arrays, the two chiral species D3-symmetry (AA,P, AA,P) and (AA,M, AA,M) as well as the meso form wifh inversion confer (AA,M, AA,P) or (AA,P, AA,M). The one-dimensional channels of fhe former appear fo be more permeable fhan fhose of fhe meso form and fhe two guest acetonitrile molecules (see bottom of Figure 133) can be removed buf fhe framework then collapses. 

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