摘要
在MP2/aug-cc-pVTZ水平上研究了SX_2(X=F,Cl,Br)与H_2CO之间的硫键作用。研究发现:二体复合物(SX_2···H_2CO)中,硫键(X-S···O)的键能(ΔE),临界点处的电子密度(ρ_b)~([1])以及特定轨道间的二阶稳定化能E(2)均按照X=F,Cl,Br的顺序依次减小。能量分解表明,硫键作用主要由电子给体和电子供体之间轨道作用的驱动,其次是静电作用。三分子复合物(SX_2···H_2CO···SX_2)包含两个S···O键,其硫键键长、临界点处的电子密度以及二阶稳定化能均较相应二体复合物的数值减小,表明第二个硫键的形成,削弱了第一个硫键,即存在反协同作用。此外,三体相互作用能(△~3E)~([2])是正值也与反协同作用一致。
Theoretical studies on the chalcogen bonding interactions of SX_2(X=F, Cl, Br) and H_2CO were investigated at the MP2/aug-cc-pVTZ level.Results show that for the bimolecular complexes, the interaction energies(ΔE), electron densities at the chalcogen bond critical point(ρb), and the second-order perturbation energy(E(2)), all decrease in sequence of X = F, Cl, Br.The energy decomposition analysis indicates the chalcogen bond interactions are mainly driven by the donor and acceptor orbital interactions, followed by electrostatic interactions.All the termolecular complexes contain two S···O bonds.And they exhibit negative cooperativity between them with longer bond lengths, smaller values of ρb and E(2).That is, the first chalcogen bond interaction is weakened when the second chalcogen bond is formed.In addition, three-body interaction energies are positive, corresponding to the negative cooperativity.
引文
[1]Bader RFW.Atoms in molecules:a quantum theory.Oxford University Press,Oxford,1990.
[2]Xantheas,S.S.J Chem Phys.1994,100:7523.
