Dimelamines-cyanurate assemblies

These double rosettes can be easily extended to tetrarosettes by connecting two calix[4]arene dimelamines by a flexible linker unit X (Figure 4.3).11,12 A tetrarosette assembly consists of fifteen components, three tetramelamines 2 and twelve barbiturate/cyanurate derivatives held together by 72 hydrogen bonds and it has a size of 3.0 x 3.1 x 2.7 nm. The thermodynamic equilibrium for the assembly 23 (DEB)i2 is reached within seconds after mixing the two different components. Similarly, hexarosettes 33 (DEB)ig are prepared... 

The multimeric assembly reported in Fig. 6 forms spontaneously when three calix[4]arene dimelamine units and six barbiturates or cyanurate are mixed in a 1 2 ratio in apolar solvents. These assemblies, made of nine achiral com-... 

Similar chiral supramolecular assemblies are also observed from achiral calix[4]arene dimelamine derivatives with chiral cyanurates thus leading to D3 symmetry species [21]. Analogously to chiral dimelamines, predominantly one of the two possible diastereomeric double-rosette assemblies was observed in most cases and it is noteworthy that the same (R) chiral moiety when mounted in the dimelamine is located on the left-hand side of the calix[4]arene and induces (M) chirality, while when implemented in the cya-nurate is placed on the right-hand side and therefore promotes P chirality (Fig. 8). 

Exploiting the same concept, Reinhoudt and Shinkai were able to obtain another example of enantioenriched chiral double-rosette made of achiral components. In this case achiral calix[4]arene bearing dimelamine moieties with pyridine functionalities were assembled with achiral cyanurate leading to racemic chiral double rosettes. The latter are perfect counterparts for chiral D-dibenzoyl tartaric acid via two-point hydrogen-bonding interactions thus... 

Both groups employed the same rationale the self-assembly of dimelamine derivative with a dicyanu-rate derivative in which the spatial distance between the two cyanurate units is different from the distance between the two melamine units. It was anticipated that this mismatch prevented the formation of a closed disklike assembly and induced the formation... 

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>. 

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