阳离子－π体系相互作用的理论研究 2: 铵离子－二苯复 合物体系的密度泛函 研究

运用密度泛函B3LYP/6-31G^*方法对离子-二苯复合物体系的可能构型进行了结构优化,得到了复合物的能量低构型为:铵离子位于两个苯环平面之间分别以两个氢原子和苯环作用,频率计算结果表明该构型为稳定结.复全物的键长、原子净电荷、分子轨道系数、前沿轨道能量、Mullicken键级等都表明，铵氢原子和与之接近的苯环碳原子之间通过s-π相互作用而实现铵与两个苯环的结合,结合时电子从苯环向铵转移复合物.它们之间的结合方式和铵离子－苯复合物及典型键的结合方式相似,计算得到的热力学参数证明了这一点.复合物的红外特征振动频率位于230cm^-^1附近,振动方式为铵平行于苯平面来回振动。

Theoretical Studies on Cation - n Interactions II . Density - Functional Theory Investigation on the Configurations of and Interactions in Ammonium Cation - Bibenzene Complexes

Density - functional theory (DFT) B3lLYP/6 - 31G^* approach has been employed to calculate the possible configurations ammonium - bibenzene (C~6H~6…NH~4^+…C~6H~6) complex. The calculation results indicate that the most stable structure of the complex is the configuration where the ammonium cation located between two benzenes with two hydrogen atoms pointing to each benzene ring.The calculated IR spectrum shows that the geometry is reasonable.The bond length, total atomic charges,the coefficiet of the molecularorbital, frontier orbital energys, and Mullicken bonding population of the complex indicate that the binding between the ammonium and two benzenes involved the s-π interaction between hydrogens of ammonium and the carbon atoms of benzenes near to the hydrogens of ammonium, with electron transfer occured from the two benzne rings to ammonium,forminmg a charge transfer complex.The calculated results also imply that,similar to that of the ammonium caton-benzene transfer complex, the interaction characteristic of the ammonium cation-bibenzene complex is a typical hydrogen bond.The calculated thermodynamic parameters demonstrate this feature.The nomal mode analysis of the predicted vibrational frequency shows that the characteristic vibration mode of the complex is located at about 230cm^-^1, correspondeding to the back and forth vibration of the ammonium cation paralleled to the bezene rings.