On the Importance of Halogen Bonding Interactions in Two X-ray Structures Containing All Four (F, Cl, Br, I) Halogen Atoms

Dmitriy F. Mertsalov,Vladimir P. Zaytsev,Eugeniya V. Nikitina,Mikhail S. Grigoriev,Fedor I. Zubkov,Rosa M. Gomila,Antonio Frontera

doi:10.3390/cryst11111406

Abstract

This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density at the heavier halogen atoms provokes the formation of multiple Ha···Ha contacts in the solid state. That is, the heavier Ha-atoms exhibit a region of positive electrostatic potential (σ-hole) along the C–Ha bond and a belt of negative electrostatic potential (σ-lumps) around the atoms. The halogen bonding assemblies in both compounds were analyzed using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, the quantum theory of “atom-in-molecules” (QTAIM), the noncovalent interaction plot (NCIplot), and the electron localization function (ELF).

Highlights

A profound comprehension of noncovalent interactions is needed to succeed in the competitive field of supramolecular chemistry [1]
The preparation and solid state characterization of halogenated compounds is of interest to further understand the behavior and directing role of halogen bonding (HaB)
BBootthh ccoommppoouunnddss ffoorrmm interestinngg 1D supramolecular assemblies in the solid state that propagate by multiple halogen atoms (Ha)···Ha contacts, that were analyzed using density functional theory (DFT) calculations

Summary

Introduction

A profound comprehension of noncovalent interactions is needed to succeed in the competitive field of supramolecular chemistry [1]. The preparation and solid state characterization of halogenated compounds is of interest to further understand the behavior and directing role of HaBs. The Wagner–Meerwein rearrangement is a well-known synthetic transformation in which a group (or H-atom) migrates from one carbon to a neighboring carbon [11,12], promoted by Lewis [13] or a Brønsted acids [14]. It was shown that N-bromosuccinimide (NBS) or bromine and iodine or ICl are the best reagents for halogenpromoted skeletal rearrangements in bridge systems such as 4a,7-epoxyisoquinolines, 3a,6-epoxyisoindoles, and 4,6-epoxycyclopenta[c]pyridines [17,19,20,21]. Crystals 2021, 11, 1406 halogen-promoted skeletal rearrangements in bridge systems such as 4а,7-epoxyisoquinolines, 3a,6-epoxyisoindoles, and 4,6-epoxycyclopenta[c]pyridines [17,19,20,21].

XRD Experimental Part

Computational Details

Structural Description of Compounds 3 and 4

DFT Calculations