Paramagnetic NMR used to probe covalent character of halogen bonds

Scientists in Czechia have devised a new method to assess the covalency of halogen bonds. By evidencing to what degree electrons are shared in this context, the method will contribute to ongoing debates on the physical nature of these increasingly important supramolecular interactions. 

Akin to better-known hydrogen bonds, halogen bonds are crucial in the fields of catalyst, drug and materials design. They occur between different molecules or within the same molecule when a nucleophilic region, such as a lone pair of electrons, on one atom is attracted to the electrophilic region, the σ hole, on a halogen atom. And they depend on the polarisability and electronegativity of the halogen (X) as well as the electron withdrawing capacity of the group to which the halogen is bonded to (R).