含有 Xe-N 三鍵之分子與陰離子以及含有多個 Xe 原子之聚合分子的理論研究

Theoretical study on molecules and anions containing Xe-N triple bonds and on polymeric Xe-containing molecules.

邱政文(Ciou Jneng-Wun)

指導教授 ： 胡維平

國立中正大學/理學院/化學暨生物化學系/碩士(2013年)

摘要

本篇論文主要分為三部分，在第一章中，我們探討含一個 N-Xe 参鍵的鈍氣化合物及陰離子。以往的研究顯示NXeO2- 與 NXeO3- 這兩個陰離子是穩定的，在此章中我們延伸討論，將部分 O 原子以 F 原子取代，形成一系列含 N-Xe 鍵之中性分子與陰離子，其通式為 NXeOnFm。我們使用全初始法 (ab initio method) 中的 MP2、CCSD(T) 方法，及密度泛函理論 (hybrid DFT) 中的 B3LYP 與 MPW1PW91方法進行計算，結果顯示 NXeOF3, NXeF3, NXeF5, NXeOF4-, NXeOF2-, NXeF4- 這些 Xe 化合物，具有短的 N-Xe 鍵，其鍵長約為 1.80 Å，且具有相當的動力學穩定性，推測其可以在低溫的環境下穩定存在。
在第二章中，我們探討含有 Xe-C 鍵之「有機」鈍氣化合物，我們嘗試將 NXeOnFm 之中性分子或陰離子，以等電子的 CH 基團取代 N 原子，以等電子的 CH2 基團取代 O 原子，以等電子的 CH3 基團取代 F 原子，形成一系列含 Xe-C 鍵之鈍氣分子，NXeO2CH2-、 NXeOCH2-、 NXeF4CH3、 NXeO2FCH3-、NXeF3CH3-、 CHXeO2- 與 CHXeO3- ；我們使用全初始法 (ab initio method) 與密度泛函理論 (hybrid DFT) 進行計算，探討其結構與穩定性，計算結果顯示大部分的這類分子可能會有能量較低的異構物存在，而且轉換的能量障礙很低，造成它們不易被觀察到，僅 NXeO2CH2- 不易產生異構物，且具有熱力學與動力學穩定性，或許能夠於低溫下穩定存在。
含有多個 Xe 原子之鈍氣化合物的研究相當有限，也是我們實驗室近年來研究的重點之一。在第三章中，我們探討 F（BFOXeO）nBF2 (n = 1, 2, 3, 4) 這類含有多個 Xe 原子之化合物；我們使用 B3LYP、MPW1PW91 與 MP2 等方法計算得知其分子結構與穩定性。計算結果顯示這類分子之Xe-O 鍵之鍵長約為 2.1 Å，當 n = 1 時為 Xe(OBF2) 2，其 CCSD(T)/aptz 單點計算結果顯示 Xe-O 鍵之平均鍵能為 15.0 kcal/mol，使用 B3LYP/apdz 與 MP2/apdz 計算分解反應之反應能障，其結果分別為 54.1 與 69.6 kcal/mol，具有熱力學與動力學穩定性，低溫下能夠穩定存在，當 n = 2,3,4 時之 Xe-O 鍵之平均鍵能約為 10.0 kcal/mol，因此可以推論此類的更大型分子( n > 4) 依然會具有熱力學穩定性，低溫下有機會能夠穩定存在。

關鍵字

Xe-C ； 鈍氣 ； Xe-N

並列摘要

This thesis consists of three chapters. In the first chapter, we studied the stable noble-gas molecules or anions containing one nitrogenxenon triple bond. Starting from the two stable anions of NXeO2- and NXeO3-, we replaced some of the O atoms with F atoms. The general formula of these series neutral molecules and anions was NXeOnFm. We used the MP2 and B3LYP theory to predict the structures of NXeOnFm. The results of the calculation illustrated that the N-Xe bond lengths of the NXeOF3, NXeF3, NXeF5, NXeOF4-, NXeOF2-, and NXeF4- were short, and the average N-Xe bond length was 1.80 Å. According to the structural information and the kinetic studies of these molecules, we predicted that these molecules should be kinetically stable at the low temperature.
In the second chapter, we investigated the organic noble-gas molecules which contain the Xe-C bonds. We replaced the N atoms of the NXeOnFm molecules by the the isoelectronic CH groups, and we also substituted the O and F atoms by the CH2 and CH3 groups, respectively. The resulting molecules contain Xe-C bonds, such as NXeO2CH2-, NXeOCH2-, NXeF4CH3, NXeO2FCH3-, NXeF3CH3-, CHXeO2-, and CHXeO3- We used the MP2and B3LYP theory to study the geometries and stabilities of these organic noble-gas molecules. The computational results showed that in most cases there were more stable isomers that could be easier generated in the synthesis processes, and thus, it would be difficult to stabilize these molecules in the experiments. Among these molecules, only the NXeO2CH2= anion was found to possess the required thermodynamic and kinetic stabilities, so it could exist at the low temperature.
The theoretical studies of the noble-gas molecules containing more than one noble gas atom has been one of the important researche topics in our laboratory. In the third chapter, we studied the F(BFOXeO)nBF2 (n = 1,2,3,4) molecules. We used the ab initio methods and the hybrid DFT functional to predict the structures and stabilities of these molecules. The average Xe-O bonds were about 2.1 Å. For n = 1, the molecule is Xe(OBF2)2, and the average bond energy of the Xe-O bond was 15.0 kcal/mol at the CCSD(T)/aptz level. The decomposition reaction barriers by the B3LYP/apdz and MP2/apdz methods were 54.1 and 69.6 kcal/mol, respectively. It seems to possess the thermodynamic and kinetic stability at the low temperature. For n = 2, 3 and 4, the average bond energy of the Xe-O bond was10.0 kcal/mol. These molecules were also found to enough thermodynamic and kinetic stability, so they could exist at low temperature environment.

並列關鍵字

noble-gas ； Xe-C ； Xe-N

參考文獻

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