ゴールドクラスターの端末アルキンの結合モチーフ
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
まとめ
ターミナルアルキンは,デプロトネーションプロセスを経て安定した黄金クラスターを形成し,クラスター表面での結合と垂直の構成を明らかにします. この研究は,黄金のクラスター表面化学の理解を深める.
科学分野:
- ナノ材料科学 ナノ材料科学
- 表面化学について
- スペクトル顕微鏡検査です.
背景:
- 小型の金塊 (<2 nm) は,ポリビニルピロリドンのようなポリマーによって安定させられることが多い.
- ターミナルアルキンは,協調化学における多用途リガンドである.
- リガンド-クラスターの相互作用を理解することは,機能的なナノマテリアルの設計に不可欠です.
研究 の 目的:
- 末端アルキンで保護された黄金のクラスターを合成し,特徴づけること.
- 金のクラスター上のアルキニルリガンドの結合モチーフと界面構造を解明する.
- 金塊へのアルキン結合のメカニズムを調査する.
主な方法:
- ポリビニルピロリドンで安定した金塊を用いたリガンド交換反応.
- フーリエ変換赤外線 (FTIR) とラーマンスペクトル.
- 質量スペクトロメトリと拡張X線吸収微細構造 (EXAFS) 分析.
- 光発光スペクトロスコピー. 光発光スペクトロスコピー. 光発光スペクトロスコピー.
主要な成果:
- 末端アルキン (1-オクチン,フェニラセチレン,9-エチニルフェナントレン) は,ポリビニルピロリドンのリガンドを成功裏に置き換えた.
- 顕微鏡データにより,アルキンのデプロトン化と結合時にCC結合の弱化が確認されました.
- Au34(PA) 16とAu30(EPT) 13のような精密に定義された黄金のクラスターが合成されました.
- 質量分析により,脱水アルキン結合が確認され,EXAFSでは,ブリッジまたは空洞部位への結合が示唆されました.
結論:
- アルキンの黄金クラスターへの結合は,デプロトネーションによって発生し,安定した脱水化種を形成します.
- アルキニルリガンドは,金塊の表面に直立した構成を採用します.
- この研究は,アルキニルで保護された金塊の構造と結合に関する詳細な洞察を提供します.
関連する概念動画
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: