Characterizing Br···O Interaction in Complexes of PhBr With Cyclic Ethers

Quantum chemistry calculations are carried out to examine the Br···O interactions in a miscellany of complexes of PhBr with dimethylether and a series of saturated cyclic ethers with systematically increasing ring‐size (decreasing ring‐strain). The formation of the Br···O interactions is found to accompany shortening of the C─Br bond‐length in the complexes in comparison to PhBr alone, which reflects the predominance of the rehybridization effect over the hyperconjugative charge transfer in agreement with Bent's rule. In line with this observation, the s‐character of the C‐centric hybrid orbital of the C─Br bond is found to increase as a result of the formation of the complexes. This is further corroborated from change of the state of hybridization of the C‐centric hybrid orbital. The results of quantum theory of atoms‐in‐molecules (QTAIM) show that the Br···O interactions are primarily characterized by an electrostatic (closed‐shell) origin. The interactions are found to be of weak van der Waals type based on noncovalent interaction (NCI) analysis, and are further corroborated from ELF and LOL analyses. This study also aims to present a comparison of the quantum chemistry results on the properties of the Br···O interactions in the studied complexes as obtained using the LC‐ωPBE, B3LYP, B3LYP‐D, and O3LYP functionals.