Source of Cooperativity in Halogen-Bonded Haloamine Tetramers.

Abstract

Inspired by the isostructural motif in α-bromoacetophenone oxime crystals, we investigated halogen-halogen bonding in haloamine quartets. Our Kohn-Sham molecular orbital and energy decomposition analysis reveal a synergy that can be traced to a charge-transfer interaction in the halogen-bonded tetramers. The halogen lone-pair orbital on one monomer donates electrons into the unoccupied σ*N-X orbital on the perpendicular N-X bond of the neighboring monomer. This interaction has local σ symmetry. Interestingly, we discovered a second, somewhat weaker donor-acceptor interaction of local π symmetry, which partially counteracts the aforementioned regular σ-symmetric halogen-bonding orbital interaction. The halogen-halogen interaction in haloamines is the first known example of a halogen bond in which back donation takes place. We also find that this cooperativity in halogen bonds results from the reduction of the donor-acceptor orbital-energy gap that occurs every time a monomer is added to the aggregate.

DOI: 10.1002/cphc.201501130

Cite this paper

@article{Dominikowska2016SourceOC, title={Source of Cooperativity in Halogen-Bonded Haloamine Tetramers.}, author={Justyna Dominikowska and F. Matthias Bickelhaupt and Marcin Palusiak and C{\'e}lia Fonseca Guerra}, journal={Chemphyschem : a European journal of chemical physics and physical chemistry}, year={2016}, volume={17 4}, pages={474-80} }