结合图案的终端基在黄金集群上的结合图案
Prasenjit Maity1, Shinjiro Takano, Seiji Yamazoe
1Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Journal of the American Chemical Society
|June 1, 2013
概括
终端基因通过去质子化过程形成稳定的黄金集群,揭示它们在集群表面的结合和直立配置. 这项研究增强了对黄金集群表面化学的理解.
科学领域:
- 纳米材料科学 科学 纳米材料科学
- 表面化学 表面化学
- 频谱学是一种光谱学方法.
背景情况:
- 小黄金集群 (<2纳米) 通常由聚烯等聚合物稳定.
- 终端基是协调化学中的多功能连接体.
- 了解连接体 - 集群相互作用对于设计功能性纳米材料至关重要.
研究的目的:
- 为了合成和表征由终端基保护的黄金集群.
- 为了阐明黄金集群上的基尼尔连接体的结合图案和界面结构.
- 为了研究基因结合到黄金集群的机制.
主要方法:
- 使用聚烯立稳定黄金集群的连接物交换反应.
- 里埃变换红外光谱 (FTIR) 和拉曼光谱.
- 质谱和扩展X射线吸收细结构 (EXAFS) 分析.
- 光发光光谱学. 光发光光谱学.
主要成果:
- 终端基 (1-octyne,phenylacetylene,9-ethynyl-phenanthrene) 成功地取代了聚烯罗立的配体.
- 光谱数据证实了基的去质子化和结合后CC键的削弱.
- 精确定义的黄金集群如Au34(PA) 16和Au30(EPT) 13被合成.
- 质量分析证实了脱的基因结合,EXAFS建议结合到桥梁或空洞部位.
结论:
- 基因与黄金集群的结合通过去质子化发生,形成稳定的脱物种.
- 基尼联体在黄金集群表面上采用直立的配置.
- 该研究提供了对基尼尔保护黄金集群的结构和结合的详细见解.
相关概念视频
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
02:42Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
02:39Nomenclature of Alkynes
Alkynes are unsaturated hydrocarbons characterized by the presence of carbon-carbon triple bonds and have a general formula CnH2n-2. The nomenclature of alkynes follows a set of rules similar to alkanes and alkenes; however, alkynes bear the suffix "-yne" instead of "-ane" or "-ene." There are two approaches to naming alkynes: