HXeBr与苯和苯的衍生物弱相互作用的理论研究

Theoretical Investigation on Weak Interactions of HXeBr with Benzene and Its Derivatives

采用MP2/aug-cc-p VDZ(对于Xe和I原子采用aug-cc-p VDZ-PP基组)优化了复合物HXe Br…C_6H_5X(X=H,CH_3,NH_2,N(CH_3)_2,NHCH_3,OH,OCH_3,CN,F,Cl,Br,I,COOH,SO_3H,CF3)及单体的几何构型,详细分析了π…H键和双齿氢键两种弱相互作用类型的特征,以及不同的取代基对这两种弱相互作用能的影响.对14个双齿氢键型复合物,我们发现复合物的相互作用能与苯环衍生物(C_6H_5X)的偶极矩,复合物中Xe—Br键键长的变化,H—Xe键键长的变化和H—Xe键振动频率的变化,以及双齿氢键上Br原子和两个H原子范德华表面相互穿透距离之和均有较好的线性关系.另外,我们还发现复合物的相互作用能与双齿氢键上两个键临界点的电子密度之和,电子密度Laplacian值之和,静电势之和,以及双齿氢键和苯环碳原子形成环的环临界点处的电子密度,电子密度Laplacian值以及静电势均有着较好的线性关系.

Geometries of complexes HXe Br…C6H5X（X=H, CH3, NH2, N（CH3）2, NHCH3, OH, OCH3, CN, F, Cl, Br, I, COOH, SO3 H, CF3） and its monomers are optimized with MP2/aug-cc-p VDZ（aug-cc-p VDZ-PP for Xe and I）. The aug-cc-p VDZ-PP is a small core pseudopotential basis set. It ignores 28 electrons for Xe and I atoms. Two types of weak interactions, π…H bond and bifurcated hydrogen bonds, are analyzed in detail. The effects of substituting group of the benzene ring on the weak interaction energies are investigated. Their effects on π…H bond are different from that on bifurcated hydrogen bonds. As for the complexes with π…H bond, electron withdrawing groups reduce the interaction energies while electron donating groups increase the interaction energies. However, for the complexes with bifurcated hydrogen bonds, electron withdrawing groups increase the interaction energies while electron-donating groups decrease the interaction energies. The effects of substituting groups on geometrical parameters of HXe Br are also analyzed. As for 14 complexes of HXe Br…C6H5X with bifurcated hydrogen bonds, it is found that their weak interaction energies have very good linear relationships with dipole moments of C6H5 X, bond length changes of Xe—Br and H—Xe bonds, vibrational frequency changes of H—Xe bonds, and the sum of two interpenetration distances of Van der Waals surfaces of bromine and two hydrogen atoms which are connected to the bromine atom by hydrogen bonds. It is also found that the weak interaction energies of 14 complexes above have very good linear relationships with the sum of electron densities（r）, the sum of ▽^2r and the sum of electrostatic potentials at two critical points of bifurcated hydrogen bonds, and with the electron density, ▽^2r and the electrostatic potential at the ring critical point which is inside a ring formed by the bifurcated hydrogen bonds and two carbon atoms of the benzene ring. As for the complexes with bifurcated hydrogen bonds, the weak interaction energies between the monomers can be understood approximately as dipole-dipole interaction.