Author: ["Seda Cantekin","Diederik W. R. Balkenende","Maarten M. J. Smulders","Anja R. A. Palmans","E. W. Meijer"]
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Abstract
N,N′,N″-trialkylbenzene-1,3,5-tricarboxamides (BTAs) self-assemble by means of strong, threefold α-helix-type intermolecular hydrogen bonding into well-defined, helical, one-dimensional columnar aggregates. When a stereogenic centre is introduced into the alkyl side chains of these BTAs, strong Cotton effects are observed in dilute apolar solutions, indicating the preference for one helical conformation over the other. Here, we report the creation of a helical sense preference in self-assembled BTAs by introducing deuterium/hydrogen isotope chirality into the alkyl side chains. We determine the relative stabilities of the left- and right-handed helical conformations of these deuterated supramolecular polymers by performing a conformational analysis. Our findings show that the results of deuterium/hydrogen substitution in BTA-based supramolecular polymers and helical polyisocyanates are very similar, although the formation mechanisms differ. The selectively deuterated BTAs discussed here represent the first example of supramolecular chirality resulting from isotope substitution. Benzene-1,3,5-tricarboxamides are known to self-assemble via intramolecular hydrogen bonding into helical columnar aggregates. Here it is shown that the introduction of a stereocentre by an isotopic substitution — replacing hydrogen for deuterium on the methylene groups next to the amide — is sufficient to direct the helicity of the formed aggregate. Cite this article
Cantekin, S., Balkenende, D., Smulders, M. et al. The effect of isotopic substitution on the chirality of a self-assembled helix. Nature Chem 3, 42–46 (2011). https://doi.org/10.1038/nchem.889 