簇合物(Me_2BN_3)_n(n=1～3)结构和性质的理论研究

A Theoretical Study on the Structures and Properties of the(Me_2BN_3)_n(n=1～3) Clusters

采用密度泛函理论B3LYP／6—311＋G^6方法，计算研究了（Me2BN3）n（n=1～3）簇合物的结构和性质．研究表明，环状多聚体（Me2BN3）n（n=1～3）的优化构型均为由不同子体系的叠氮基0-N和B原予相连形成的环状结构．讨论几何参数随聚合度的变化关系，同时对所有优化构型进行振动频率计算，对其IR谱进行归属，并与实验值进行了比较，结果发现计算值均可信．簇合物的热力学函数均随簇合物的聚合度n以及温度的增加而呈线性增加．由聚合反应的焓变可知，在298．2K下单体形成三聚体在热力学上是有利的，而形成二聚体则是不利的．

The （Me2BN3）n（n=1～3） clusters were optimized to obtain their structures and properties at the DFT- B3LYP/6-31 1 ＋G＊ level. The optimized clusters （MezBN3）n（n=2-3） all possess cyclic structure formed by B atoms bridged by the α-nitrogen of the azide groups. The relationships between geometrical parameters and oligomerization degree n are discussed. Their IR spectra are obtained and assigned by vibrational analysis and are reliable compared with the experimental results. The thermodynamic properties are linearly related with the oligomerization degree n as well as the temperature. Thermodynamic analysis of the gas-phase reaction shows that formation of the stable clusters （Me2BN3）, is thermodynamically favorable by the enthalpies for n = 3, but unfavorable in the case of n = 2 at 298.2 K.