Nitrone [2]Rotaxanes: Simultaneous Chemical Protection and Electrochemical Activation of a Functional Group

Daniel M. D'Souza, David A. Leigh, Loic Mottier, Kathleen M. Mullen, Francesco Paolucci, Simon J. Teat, Songwei Zhang

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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 H-1 NMR studies of the rates of macrocycle pirouetting in nonpolar solutions indicated that the amide nitrone hydrogen bonds are particularly strong (similar to 1.3 and similar to 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.

Original languageEnglish
Pages (from-to)9465-9470
Number of pages6
JournalJournal of the American Chemical Society
Volume132
Issue number27
DOIs
Publication statusPublished - 14 Jul 2010

Fingerprint

Dive into the research topics of 'Nitrone [2]Rotaxanes: Simultaneous Chemical Protection and Electrochemical Activation of a Functional Group'. Together they form a unique fingerprint.

Cite this