两个四硫富瓦烯分子正离子自由基TTF·^＋之间的共价吸引作用

A covalent attraction between two molecular cation TTF·^+

使用MP2/6-311G方法得到了四硫富瓦烯自由基正离子二聚体(TTF·+-TTF·+)能量极小点的结构.这显示这种正离子间的吸引作用存在.这种新的吸引作用是望远镜形状的20中心2电子分子间共价π/π键.这种共价π/π键的键能约为-21kcal·mol-1,它被正离子间的库伦排斥作用掩盖.有负离子围绕的四硫富瓦烯自由基正离子二聚体(TTF·+-TTF·+)体系是稳定的.

The optimized structure of the tetrathiafulvalence radical-cation dimer （TTF·^＋ -TTF·^＋） with all-real frequencies is obtained at MP2/6-311G level, which exhibits the attraction between two molecular cation TTF·^＋ . The new attraction interaction is a 20-center-2-electron intermolecular covalent π/π bonding with a telescope shape. The covalent π/π bonding has the bonding energy of about -21 kcal·mol^-1 and is concealed by the Coulombic repulsion between two TTF·^＋ cations. This intermolecular covalent attraction also influences the structure of the TTF·^＋ subunit, i.e., its molecular plane is bent by an angle θ= 5.6°. This work provides new knowledge on intermolecular interaction.