Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA.
Phys Chem Chem Phys. 2011 Aug 21;13(31):13951-61. doi: 10.1039/c1cp20480g. Epub 2011 Jun 6.
A systematic ab initio investigation has been carried out to determine the structures, binding energies, and spin-spin coupling constants of ternary complexes X:CNH:Z and corresponding binary complexes X:CNH and CNH:Z, for X, Z = CNH, FH, ClH, FCl, and HLi. The enhanced binding energies of ternary complexes X:CNH:Z for fixed X as a function of Z decrease in the same order as the binding energies of the binary complexes CNH:Z. In contrast, the enhanced binding energies of the ternary complexes for fixed Z as a function of X do not decrease in the same order as the binding energies of the binary complexes X:CNH, a consequence of the increased stabilities of ternary complexes FCl:CNH:Z due to very strong chlorine-shared halogen bonds. For complexes in which the X···CNH interaction is a D-H···C hydrogen bond for D-H the proton-donor group (N-H, F-H, or Cl-H), spin-spin coupling constants (1)J(D-H) and (2h)J(D-C) in ternary complexes X:CNH:Z decrease in absolute value as the binding energies of binary complexes CNH:Z and the enhanced binding energies of the ternary complexes for fixed X as a function of Z also decrease. However, (2X)J(F-C) increases as the enhanced binding energies of the ternary complexes FCl:CNH:Z decrease, a consequence of the nature of the chlorine-shared halogen bond. The one-bond coupling constants (1)J(N-H) for the CNH···Z interaction in ternary complexes vary significantly, depending on the nature of the X···CNH interaction. The largest values of (1)J(N-H) are found for ternary complexes with FCl as X. Two-bond coupling constants (2h)J(N-A) for A the proton-acceptor atom of Z, and (2d)J(N-H) decrease in absolute value in the order of decreasing enhancement energies of ternary complexes X:CNH:Z for fixed Z as a function of X.
我们系统地从头算研究了三元复合物 X:CNH:Z 和相应的二元复合物 X:CNH 和 CNH:Z 的结构、结合能和自旋-自旋耦合常数，其中 X、Z = CNH、FH、ClH、FCl 和 HLi。对于固定的 X，三元复合物 X:CNH:Z 的增强结合能作为 Z 的函数降低，其顺序与二元复合物 CNH:Z 的结合能降低顺序相同。相比之下，对于固定的 Z，三元复合物的增强结合能作为 X 的函数并不按照二元复合物 X:CNH 的结合能降低顺序降低，这是由于 FCl:CNH:Z 三元复合物由于非常强的氯共享卤键而具有更高的稳定性所致。对于其中 X···CNH 相互作用是 D-H···C 氢键的复合物，对于质子供体基团（N-H、F-H 或 Cl-H），自旋-自旋耦合常数（1）J(D-H)和（2h）J(D-C)在三元复合物 X:CNH:Z 中绝对值降低，随着二元复合物 CNH:Z 的结合能降低，以及固定 X 时三元复合物的增强结合能也降低。然而，（2X）J(F-C)随着 FCl:CNH:Z 三元复合物增强结合能的降低而增加，这是由于氯共享卤键的性质所致。CNH···Z 相互作用的单键耦合常数（1）J(N-H)在三元复合物中变化很大，取决于 X···CNH 相互作用的性质。对于 X 为 FCl 的三元复合物，（1）J(N-H)的值最大。质子受体原子 Z 的 A 的二键耦合常数（2h）J(N-A)和（2d）J(N-H)的绝对值在 X 固定时，随着三元复合物 X:CNH:Z 增强能量的顺序降低而降低。
