Oliveira Vytor, Kraka Elfi, Cremer Dieter
Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas 75275-0314, USA.
Phys Chem Chem Phys. 2016 Dec 7;18(48):33031-33046. doi: 10.1039/c6cp06613e.
36 halogen-bonded complexes YXAR (X: F, Cl, Br; Y: donor group; AR acceptor group) have been investigated at the CCSD(T)/aug-cc-pVTZ level of theory. Binding energies, geometries, NBO charges, charge transfer, dipole moments, electrostatic potential, electron and energy density distributions, difference density distributions, vibrational frequencies, local stretching and bending force constants, and relative bond strength orders n have been calculated and used to order the halogen bonds according to their intrinsic strength. Halogen bonding is found to arise from electrostatic and strong covalent contributions. It can be strengthened by H-bonding or lone pair delocalization. The covalent character of a halogen bond increases in the way 3c-4e (three-center-four-electron) bonding becomes possible. One can characterize halogen bonds by their percentage of 3c-4e bonding. FCl-phosphine complexes can form relatively strong halogen bonds provided electronegative substituents increase the covalent contributions in form of 3c-4e halogen bonding. Binding energies between 1 and 45 kcal mol are calculated, which reflects the large variety in halogen bonding.
在CCSD(T)/aug-cc-pVTZ理论水平下，对36种卤键复合物YXAR（X：F、Cl、Br；Y：供体基团；AR：受体基团）进行了研究。计算了结合能、几何结构、自然键轨道（NBO）电荷、电荷转移、偶极矩、静电势、电子和能量密度分布、差分密度分布、振动频率、局部伸缩和弯曲力常数以及相对键强度顺序n，并根据其固有强度对卤键进行排序。发现卤键源于静电作用和强共价作用贡献。它可以通过氢键或孤对离域作用得到加强。当三中心四电子（3c-4e）键合成为可能时，卤键的共价特性会以这种方式增加。可以通过其3c-4e键合的百分比来表征卤键。如果电负性取代基以3c-4e卤键的形式增加共价贡献，FCl-膦配合物可以形成相对较强的卤键。计算出的结合能在1至45千卡/摩尔之间，这反映了卤键的多样性。
