Traversing the Tightrope between Halogen and Chalcogen Bonds Using Structural Chemistry and Theory

Abstract

Adjusting the physical and chemical properties of crystalline materials by controlling their structures is highly desirable in solid-state and materials chemistry. Such control can be achieved by carefully exploiting and fine-tuning the interactions between molecules. In this work, functionalized benzochalcogenadiazole molecules capable of forming two different σ-hole interactions (halogen and chalcogen bonds) are used as building blocks to assemble crystals with distinctly different structural features. Ab initio calculations are performed in order to rationalize the crystal structures obtained and to quantify the intermolecular interactions. It is found that the structural features and the balance between different interactions, as well as the relative strength of the σ-hole interactions, are highly sensitive to the identity of the halogen and chalcogen atoms in the molecules. Both electrostatic/polarization and dispersion forces play an important role in defining the energetics of the chalcogen-bonded and halogen-bonded isomers, and by a control of the balance between these components, it is possible to precisely control the point at which one type of supramolecular architecture is favored over another.

Cooperativity of Halogen- and Chalcogen-Bonding Interactions in the Self-Assembly of 4-Iodoethynyl- and 4,7-Bis(iodoethynyl)benzo-2,1,3-chalcogenadiazoles: Crystal Structures, Hirshfeld Surface Analyses, and Crystal Lattice Energy Calculations

“…In the crystal lattice of [S]­(CC-I) 2 individual dimers are further connected with each other through C–I···π­(ethynyl) XBs, creating zigzag structures (Figure b and Table ). This structure has been also reported by Aakeröy and co-workers …”

“…It is worth mentioning that the simultaneous use of XB and ChB interactions in supramolecular assemblies has been marginally investigated. , However, during the review procedure of this paper, a closely related paper dealing with the competition between different σ-hole interactions in the crystals of 4,7-dihalogeno- and 4,7-bis­(halogenoethynyl)­benzo-2,1,3-chalcogenadiazoles was published by Aakeröy and co-workers . The iodoethynyl moiety in our model compounds was chosen as a substituent because the iodine atom attached to sp-hybridized carbon tends to form strong halogen bonds .…”

Principles Guiding the Square Bonding Motif Containing a Pair of Chalcogen Bonds between Chalcogenadiazoles

“…Although not a tight rectangular arrangement, each Te could engage in a Te•••N ChB with a polybasic molecule, leading to a supramolecular synthon. Panikkattu et al 51 compared the ability of functionalized benzochalcogenadiazoles to engage in ChB versus the halogen bonds that might occur with halogen atoms on the substituents. The rectangular ChB arrangement was preferred for the lighter Cl substituents.…”

“…The bonding pattern is strong enough that it persists even in the gas phase without any external structural constraints or when the species are present as open-shell radicals or even as like-charged cations . The groups can be bound together strongly enough that these chalcogen bonds outweigh the alternate possibility of halogen bonds . This motif may have useful applications as in the assembly of a porous organic framework …”

“…50 The groups can be bound together strongly enough that these chalcogen bonds outweigh the alternate possibility of halogen bonds. 51 This motif may have useful applications as in the assembly of a porous organic framework. 52 The potential usefulness of this bonding motif, coupled with the paucity of detailed information about it, warrants a systematic study to answer some of the following questions.…”