Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer’s Dance

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• 作者：Karlos X. Moreno ; Eric E. Simanek
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：June 24, 2008
• 年：2008
• 卷：41
• 期：12
• 页码：4108 - 4114
• 全文大小：1862K
• 年卷期：v.41,no.12(June 24, 2008)
• ISSN：1520-5835

文摘

One-dimensional (1D) and two-dimensional (2D) NMR studies are used to probe the conformation of a melamine dendrimer bearing unique NMR signals from the core to the periphery. Four conceptual anchors for dendrimer conformation emerge from these experiments. First, changes in isomer populations observed by ¹H NMR reveal the onset of globular structure. Second, NOE complexity emerges with globular structure: variable temperature NOESY studies show that the peripheral groups, BOC-protected aliphatic amines, fold back into the globular core of the macromolecule at 75 °C in DMSO-d₆. Third, variable temperature coefficients measured for NH protons suggest that solvent is largely excluded from the interior of the dendrimer: the carbamate NH groups of the periphery are most sensitive to temperature while the NHs nearest the core show little temperature dependence. Conformation is influenced by solvent choice: backfolding is observed in DMSO-d₆, but not in either CDCl₃ or CD₃OD. Finally, relaxation studies show that peripheral groups are more dynamic than groups at the core. These anchors consolidate observations made by many groups on disparate systems within a common architecture.