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rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
2010-7-7
pubmed:abstractText
We report on the use of the hydrogen-bond-accepting properties of neutral nitrone moieties to prepare benzylic amide macrocycle-containing [2]rotaxanes in yields as high as 70%. X-ray crystallography showed the presence of up to four intercomponent hydrogen bonds between the amide groups of the macrocycle and the two nitrone groups of the thread. Dynamic (1)H NMR studies of the rates of macrocycle pirouetting in nonpolar solutions indicated that the amide-nitrone hydrogen bonds are particularly strong (approximately 1.3 and approximately 0.2 kcal mol(-1) stronger than similar amide-ester and amide-amide interactions, respectively). In addition to polarizing the N-O bond through hydrogen bonding, the rotaxane structure affects the chemistry of the nitrone groups in two significant ways: first, the intercomponent hydrogen bonding activates the nitrone groups to electrochemical reduction, a one-electron-reduction of the rotaxane being stabilized by a remarkable 400 mV (8.1 kcal mol(-1)) with respect to the same process in the thread; second, however, encapsulation protects the same functional groups from chemical reduction with an external reagent (and slows electron transfer to and from the electroactive groups in cyclic voltammetry experiments). Mechanical interlocking with a hydrogen-bonding molecular sheath thus provides a route to an encapsulated polarized functional group and radical anions of significant kinetic and thermodynamic stability.
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
Jul
pubmed:issn
1520-5126
pubmed:author
pubmed:issnType
Electronic
pubmed:day
14
pubmed:volume
132
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9465-70
pubmed:year
2010
pubmed:articleTitle
Nitrone [2]rotaxanes: simultaneous chemical protection and electrochemical activation of a functional group.
pubmed:affiliation
School of Chemistry, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JJ, United Kingdom.
pubmed:publicationType
Journal Article