Supramolecular synthons based on halogen bonding have been identified as excellent tools for the design and synthesis of supramolecular architectures. This growing field in crystal engineering has led to many discoveries of new and exciting intermolecular bonding motifs.
In this advance article, Kari Raatikainen and Kari Rissanen from the University of Jyväskylä report extremely short X···N synthons (where X= Br, I) from the crystal structures of N-haloimides with a series of amines and identify a unique example of a halogen bond based tubular material.
X-ray structure analyses reveal that X···N (X = Br, I) distances range from 2.347 Å to 2.596 Å. These unusually short halogen bond distances suggest an extremely polarized halogen atom, which allows exceptionally large overlap of Van der Waals volumes with the donor atom. The tetrahedral arrangement of N-iodosuccinimide with tetrafunctional hexamethylenetetramine exhibits these very strong halogen bonds, as well as multiple weak C-H···O hydrogen bonds, to form infinite channels with 7.31 Å × 6.74 Å diameter along the crystallographic c axis. The properties of this complex as a porous material are currently under investigation.
Interaction between amines and N-haloimides: a new motif for unprecedentedly short Br···N and I···N halogen bonds
Kari Raatikainen and Kari Rissanen
CrystEngComm, 2011, Advance Article DOI:10.1039/C1CE05447C