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Reactive Pseudorotaxanes: Inclusion Complexation of Reduced Viologens by the Hosts β‐Cyclodextrin and Heptakis(2,6‐di‐o‐Methyl)‐β‐Cyclodextrin
Author(s) -
Mirzoian Armen,
Kaifer Angel E.
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030711
Subject(s) - chemistry , cyclodextrin , viologen , aqueous solution , solubility , medicinal chemistry , alkoxy group , ethanol , cucurbituril , stereochemistry , organic chemistry , molecule , supramolecular chemistry , alkyl
The complexation of three guests containing 4,4′‐bipyridinium redoxactive residues by β‐cyclodextrin (β‐CD) and its heptakis‐(2,6‐ O ‐dimethyl) analogue (DM‐β‐CD) was investigated by means of voltammetric techniques. The three 4,4′‐bipyridinium (viologen) derivatives used as guests were designed to be water‐soluble in all three accessible oxidation states. The N ‐substituents chosen to enhance aqueous solubility were: 2‐(2‐(2‐ethoxy)ethoxy)ethanol (guest 1 2+ ), 6‐hexanoate (guest 2 ), and 3‐propanesulfonate (guest 3 ). Detailed analysis of the voltammetric results by digital simulation techniques revealed that the oxidized forms of the guests did not interact appreciably with either CD host; the two‐electron reduced guests formed extremely stable inclusion complexes, with association constants in the range 10 3 –10 4 M −1 , while the cation radical forms exhibited intermediate binding affinities (≈10 2 M −1 ). In all cases, DM‐β‐CD was found to form more stable complexes than unmodified β‐CD.