Hydrogen Bonded Semi-Rigidified Bispyridyl-Incorporating Aryl Amide Oligomers: Efficient "C"-Styled Receptors for Aliphatic Ammoniums, a Remarkable Protonation Effect and Chiral Induction

The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid (TFA) salts of n‐dodecylamine, di‐n‐octylamine, n‐dodecyl D‐ and L‐phenylalaninates (3, 4, and D‐ and L‐5) in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridy...

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Bibliographic Details
Published in:Chinese journal of chemistry 2007-10, Vol.25 (10), p.1417-1422
Main Authors: LI, Chang-Zhi, LI, Zhan-Ting, GAO, Xiang, WANG, Quan-Rui
Format: Article
Language:English
Subjects:
aliphatic ammonium
circular dichroism
foldamer
hydrogen bonding
molecular recognition
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Summary:The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid (TFA) salts of n‐dodecylamine, di‐n‐octylamine, n‐dodecyl D‐ and L‐phenylalaninates (3, 4, and D‐ and L‐5) in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridyls at the terminals which are connected directly or with an acetylene linker. The rigidified folded moieties are stabilized by intramolecular hydrogen bonding, while the whole molecules can adopt an "S"‐ or a "C"‐styled conformation depending on the relative orientation of the two rigidified moieties. 1H NMR, UV‐Vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium cations with their "C"‐styled conformation. In the presence of 1 equiv. of TFA, the binding stability was increased significantly as a result of promoted formation of the "C"‐styled conformation due to the monoprotonation of the peripheral pyridyl units in 1 and 2. In contrast, the addition of 2 equiv. of TFA substantially weakened the binding stability because the "S"‐styled conformation was favored as a result of protonation of both of their pyridyl units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D‐ and L‐5.
ISSN:1001-604X
1614-7065
DOI:10.1002/cjoc.200790262