A DFT study of Lp···π/halogen bond competition in complexes of perhalogenated alkenes with oxygen/nitrogen containing simple molecules

The possible noncovalent lone pair‐π/halogen bond (lp···π/HaB) complexes of perhalogenated unsaturated C₂Cl_nF_4?n (n = 0–4) molecules with four simple molecules containing oxygen or nitrogen as electron donor, formaldehyde (H₂CO), dimethyl ether (DME), NH₃, and trimethylamine (TMA), have been systematically examined at the M062X/aug‐cc‐pVTZ level. Natural bond orbital (NBO) analysis at the same level is used for understanding the electron density distributions of these complexes. The progressive introduction of Cl atom on C₂Cl_nF_4?n influences more on the lp···π complexes over the corresponding HaB ones. Within the scope of this study, gem‐C₂Cl₂F₂ is the best partner molecule for lp···π interaction with the simple molecules, coupled with the greatest interaction energy (IE) and second‐order orbital interaction E(2) value], whereas C₂F₄ is the poorest one. The C₂Cl₃F·H₂CO and C₂Cl₄·H₂CO complexes exhibit reverse lp···π bonding, while the Z/E‐C₂Cl₂F₂·NH₃, C₂Cl₃F·NH₃ and C₂Cl₄·NH₃ complexes perform half‐lp···π bonding according to the NBO analysis. The lp···π interaction involving the oxygen/nitrogen and the π‐hole of C₂Cl_nF_4?n overwhelms the HaB involving the oxygen/nitrogen and the σ‐hole of the Cl atom. The electron‐donating methyl groups contribute significantly to the two competitive interactions, therefore, DME and TMA engage stronger in the partner molecules than H₂CO and NH₃. Our theoretical study would be useful for future experimental investigation on noncovalent complexes. © 2016 Wiley Periodicals, Inc.