New dendrimers containing a single cobaltocenium unit covalently attached to the apical position of Newkome dendrons: Electrochemistry and guest binding interactions with cucurbit[7]uril

David Sobransingh, Angel E. Kaifer

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

Two new dendrimer series were prepared and characterized. These dendrimers contain a single bis(cyclopentadienyl)-cobalt(III) (cobaltocenium, Cob +) unit covalently attached to the apical (focal) position of Newkome-type dendrons, ranging in size from first to third generation. The dendrimers in the first series (1ECob+ - 3ECob+) are hydrophobic and have 3, 9, and 27 tert-bulyl esters on their peripheries, whereas the dendrimers in the second series (1Cob+ - 3Cob +) are hydrophilic with 3, 9, and 27 carboxylic acid groups on their surfaces, respectively. In voltammetric experiments, all dendrimers showed the expected one-electron reversible reduction of the cobaltocenium center, and the heterogeneous rate of electron transfer decreased with generation in both dendrimer series. The host - guest binding interactions between water-soluble dendrimers 1Cob+ - 3Cob+ and the cucurbit[7]uril (CB7) host were investigated using 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and electrochemical techniques. The association equilibrium constants (K) for all dendrimer guests were significantly lower than that measured for the inclusion complex between underivatized Cob+ and CB7 (K = 5.7 × 109 M-1)- Nonetheless, among the three dendrimers surveyed, the second-generation dendrimer, 2Cob+, afforded optimum stabilization for the CB7 inclusion complex.

Original languageEnglish (US)
Pages (from-to)10540-10544
Number of pages5
JournalLangmuir
Volume22
Issue number25
DOIs
StatePublished - Dec 5 2006

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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