Halogen and Hydrogen Bond Motifs in Ionic Cocrystals Derived from 3-Halopyridinium Halogenides and Perfluorinated Iodobenzenes.

Lidija Posavec,Vinko Nemec,Vladimir Stilinović,Dominik Cinčić

doi:10.1021/acs.cgd.1c00755

Abstract

Four halopyridinium salts, 3-chloro- and 3-bromopyridinium chlorides and bromides, have been successfully cocrystallized with two ditopic perfluorinated iodobenzenes, 1,4-diiodotetrafluorobenzene and 1,2-diiodotetrafluorobenzene. These halogen bond donor molecules were chosen because the different positionings of halogen bond donor atoms can lead to different supramolecular architectures. In this work, we present insight into the halogen bond acceptor potential of chloride and bromide ions, as well as the halogen bond donor potential of chlorine and bromine atoms substituted on the pyridinium ring when combined with the expectedly very strong hydrogen bonds between halopyridinium ions and free halogenide anions. A series of eight cocrystals were obtained in which three pairs of isostructural cocrystals were formed. Dominant interactions in the obtained cocrystals were charge-assisted hydrogen bonds between halopyridinium cations and halogenide ions as well as halogen bonds between halogen atoms on the pyridinium ring and halogenide ions.

Highlights

Four halopyridinium salts, 3-chloro- and 3-bromopyridinium chlorides and bromides, have been successfully cocrystallized with two ditopic perfluorinated iodobenzenes, 1,4-diiodotetrafluorobenzene and 1,2-diiodotetrafluorobenzene
Halogenide ions have been studied as hydrogen bond acceptors in simple salts, organic cocrystals, and complex metal−organic systems and as anion receptors and sensors.[26−28] They have been proven to be good halogen and hydrogen bond acceptors because of the large charge density.[29−31] As a result of their sphericity, halogenide ions provide for the possibility of establishing a range of supramolecular interactions with different resultant network geometries and topologies.[32−38] The number of halogen bonds formed with the anion in the crystal varies and depends on the molecules of which the multicomponent system consists, as well as the geometric requirements of the crystal packing
One can find studies of halogen bonding involving halogenide ions in halopyridinium and haloanilinium salts, cocrystals containing metal complex subunits, cryptated derivatives, quaternary ammonium ions, spiropyran derivatives, etc.[41−47] While there is a good amount of halogen-bonded structures containing halogenide ions present in the Cambridge Structural Database,[48] there are few data sets and studies of ionic cocrystals containing perfluorinated iodobenzenes

Summary

■ ACKNOWLEDGMENTS

This research was supported by the Croatian Science Foundation under the project IP-2014-09-7367 and project IP-2019-04-1868. We acknowledge the support of project CIuK cofinanced by the Croatian Government and the European Union through the European Regional Development Fund-Competitiveness and Cohesion Operational Programme (Grant KK.01.1.1.02.0016.).

■ REFERENCES

Findings

Benchmarking of Halogen Bond Strength in Solution with Nickel