Synthesis, Characterization, and Surface Tethering of Sulfide-Functionalized Ti16-oxo-alkoxy Cages

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• 作者：Salvador Eslava ; Anthoula C. Papageorgiou ; Simon K. Beaumont ; Georgios Kyriakou ; Dominic S. Wright ; Richard M. Lambert
• 刊名：Chemistry of Materials
• 出版年：2010
• 出版时间：September 28, 2010
• 年：2010
• 卷：22
• 期：18
• 页码：5174-5178
• 全文大小：811K
• 年卷期：v.22,no.18(September 28, 2010)
• ISSN：1520-5002

文摘

The parent cage [Ti₁₆O₁₆(OEt)₃₂] readily undergoes ligand exchange with a range of primary alcohols to yield species of the type [Ti₁₆O₁₆(OEt)_32−x(OR′)_x], with R′ = Me, n-Pr, and n-Bu with x of up to 8. Attempted ligand exchange using the thiol [HO(CH₂)₄SH] in an attempt to produce functionalized cages suitable for tethering to Au surfaces failed, resulting only in the polymerization of the Ti oxo-cores. However, the use of the thioether [HO(CH₂)₄SCH₃] resulted in successful thio-functionalization and preservation of the Ti₁₆ cage core, likely due to methyl protection on the sulfide which precludes further intermolecular reaction with other cage molecules. ESI-MS and NMR showed that the resulting substituted cage [Ti₁₆O₁₆(OEt)₂₄{O(CH₂)₄SCH₃}₈] contained eight methylthio-n-butoxy ligands in two groups of four pseudoequivalent positions. High resolution XPS and STM demonstrated that this sulfide-functionalized cage underwent covalent tethering to Au surfaces involving five sulfur linkages per cage, forming a monolayer of adsorbed species in which the molecular integrity had been preserved. In contrast, the parent oxo-alkoxy cage underwent extensive decomposition, rendering it useless as a building block for specific surface architectures.