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 C 2 Cl n F 4− n ( n  = 0–4) molecules with four simple molecules containing oxygen or nitrogen as electron donor, formaldehyde (H 2 CO), dimethyl ether (DME), NH 3 , 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 C 2 Cl n F 4− n influences more on the lp···π complexes over the corresponding HaB ones. Within the scope of this study, gem‐C 2 Cl 2 F 2 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 C 2 F 4 is the poorest one. The C 2 Cl 3 F·H 2 CO and C 2 Cl 4 ·H 2 CO complexes exhibit reverse lp···π bonding, while the Z/E‐C 2 Cl 2 F 2 ·NH 3 , C 2 Cl 3 F·NH 3 and C 2 Cl 4 ·NH 3 complexes perform half‐lp···π bonding according to the NBO analysis. The lp···π interaction involving the oxygen/nitrogen and the π‐hole of C 2 Cl n F 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 H 2 CO and NH 3 . Our theoretical study would be useful for future experimental investigation on noncovalent complexes. © 2016 Wiley Periodicals, Inc.