Investigating CS···I Halogen
Bonding for Cocrystallization with Primary Thioamides
- Publication date
- Publisher
Abstract
Cocrystallization
utilizing halogen bonding involving the thiocarbonyl
functional group of a series of primary aromatic thioamides has been
investigated. The well-known organoiodide 1,4-diiodotetrafluorobenzene
was utilized as the halogen bond donor and the CS···I
halogen bond was established as a robust supramolecular synthon in
these systems. Weak N–H···S hydrogen bonding
involving the thioamides influences the overall supramolecular architectures,
meaning that there is a diverse range of structural motifs and cocrystal
stoichiometries observed. The majority (60%) of the cocrystals obtained
have a 2:1 ratio of thioamide/organiodide with the latter present
over an inversion center. The higher ratio of organoiodide seen in
the other cocrystals is achieved by additional I···I
and I···π halogen bonding. The CS···I
halogen bond is replaced by N···I halogen bonding in
the one cocrystal containing a pyridyl-substituted thioamide. The
ability of the thioamides to form cocrystals and the strength of the
halogen bond were influenced by the nature of the substituents on
the aromatic ring, with derivatives containing electron donating groups
most likely to form cocrystals. Calculated molecular electrostatic
potential values on the sulfur atom in the thioamides corroborate
these experimental results