Abstract
In this work, we describe a novel halogen-bonded metal-organic cocrystal involving a square-planar Cu(ii) complex and 1,4-diiodotetrafluorobenzene (14tfib) by utilizing an amine ligand whose pendant acetyl group enables halogen bonding. The cocrystal was prepared by both mechanochemical synthesis (liquid-assisted grinding) and the conventional solution-based method. Crystal structure determination by single crystal X-ray diffraction revealed that the dominant supramolecular interactions are the I···O halogen bond between 14tfib and CuCl2(aap)2 building blocks, and the N–H···Cl hydrogen bonds between CuCl2(aap)2 molecules. The combination of halogen and hydrogen bonding leads to the formation of a 2D network. Overall, this work showcases an example of the possibility for extending the complexity of metal-organic crystal structures by using halogen bonding in a way that does not affect other hydrogen bonding synthons.
Highlights
In the past three decades, the halogen bond has increasingly proven itself as a supramolecular interaction that can be used alongside the well-researched hydrogen bond in crystal engineering [1,2,3]
The CuCl22 complex was synthesized by reacting copper(ii) chloride dihydrate and the aap ligand
Our screening for cocrystal formation of the obtained complex was based on mechanochemical liquid-assisted grinding followed by plexiglass jar and (PXRD) analysis
Summary
In the past three decades, the halogen bond has increasingly proven itself as a supramolecular interaction that can be used alongside the well-researched hydrogen bond in crystal engineering [1,2,3]. The data obtained show that there are fewer cases where halogen bonds are formed with monodentate organic ligands than cases where they are formed with bidentate organic ligands, or directly bound halide or pseudohalide (CN− , SCN− , OCN− , and similar) ligands This is presumably because metal complexes that have monodentate ligands are less stable in solution in comparison to chelate metal complexes containing bidentate ligands [44], so the decomposition of the metal complex in solution significantly hinders the desired cocrystallization of the complex subunits with the halogen bond donor.
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