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
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- 作者：David Sobransingh ; Angel E. Kaifer
- 刊名：Langmuir
- 出版年：2006
- 出版时间：December 5, 2006
- 年：2006
- 卷：22
- 期：25
- 页码：10540 - 10544
- 全文大小：183K
- 年卷期：v.22,no.25(December 5, 2006)
- ISSN：1520-5827
文摘
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 hydrophobicand have 3, 9, and 27 tert-butyl 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 voltammetricexperiments, all dendrimers showed the expected one-electron reversible reduction of the cobaltocenium center, andthe heterogeneous rate of electron transfer decreased with generation in both dendrimer series. The host-guest bindinginteractions between water-soluble dendrimers 1Cob+-3Cob+ and the cucurbit[7]uril (CB7) host were investigatedusing 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and electrochemical techniques. The associationequilibrium constants (K) for all dendrimer guests were significantly lower than that measured for the inclusioncomplex between underivatized Cob+ and CB7 (K = 5.7 × 109 M-1). Nonetheless, among the three dendrimerssurveyed, the second-generation dendrimer, 2Cob+, afforded optimum stabilization for the CB7 inclusion complex.