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

Abstract

The possible noncovalent lone pair‐π/halogen bond (lp···π/HaB) complexes of perhalogenated unsaturated C2ClnF4−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 C2ClnF4−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 C2ClnF4−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.