Counterion influence on the N-I-N halogen bond
Artikel i vetenskaplig tidskrift, 2015

A detailed investigation of the influence of counterions on the [N–I–N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N–I–N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(I) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(I) complexes are converted into multi-coordinate geometries with strong Ag–O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N–I–N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.


halogen bond

chemical bond



Michele Bedin

Göteborgs universitet

Alavi Karim

Göteborgs universitet

Marcus Reitti

Göteborgs universitet

Anna-Carin Carlsson

Göteborgs universitet

Filip Topic

M Cetina

Fanfang Pan

V. Havel

Fatima Al-Ameri

Göteborgs universitet

Vladimir Sindelar

Kari Rissanen

Jürgen Gräfenstein

Göteborgs universitet

Mate Erdelyi

Göteborgs universitet

Chemical Science

2041-6520 (ISSN) 2041-6539 (eISSN)

Vol. 6 7 3746-3756


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