Theoretical insight into the interplay between lithium and halogen–hydride bonds: An ab initio study

Quantum chemical calculations have been performed to analyze the intermolecular interactions in the ternary NCLi ⋯ NCX ⋯ HMgY complexes ( X = F , Cl , Br ; Y = H , F , Cl , Br , Li ). A cooperative effect is observed between the lithium and halogen–hydride bonds in these complexes. The cooperative energy ranges from -1.81 kJ/mol to -5.21 kJ/mol, -3.59 kJ/mol to -9.86 kJ/mol and -4.77 kJ/mol to -14.27 kJ/mol for X = F , Cl and Br , respectively (at MP2/6-311++G(d,p) level). The geometrical and interaction energies analysis reveal that the lithium bond has a greater enhancing effect on the halogen–hydride bond. The results of many-body analysis indicate that two- and three-body interaction energies have a positive contribution to the total interaction energy. The electronic characteristics of the complexes have been analyzed through molecular electrostatic potential (MEP), atoms in molecules (AIM), electron localization function (ELF) and natural bond orbital (NBO) methodologies.

Cooperative interaction between hydrogen bond and N···Y interactions (Y = H, Li, F, Cl, and Br): a comparative study

A comparative ab initio study is performed to investigate the cooperativity between the N···H hydrogen bond and the N···Y interactions in XCN···HCN···YCN complexes, where X = H, F, and Y = H, Li, F, Cl, and Br. To understand the properties of the systems better, the corresponding dimers are also studied. It is found that the lithium bond has a larger influence on the hydrogen bond than vice versa. The shortening of the N···H distances in the trimers is dependent on the strength of the H···Y interactions and they become larger in the order lithium bond > hydrogen bond > halogen bond. The estimated values of cooperative energy Ecoop are all negative with much larger Ecoop in absolute value for the systems including lithium.