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.

N-Oxide–N-oxide interactions and Cl...Cl halogen bonds in pentachloropyridine N-oxide: the many-body approach to interactions in the crystal state

“…This indicates a weak cooperative effect of the halogen bonding within the investigated complex. This result is in agreement with earlier studies on similar halogen-bonded cyclic complexes for which very weak cooperativity or even anticooperativity was usually observed (Dominikowska & Palusiak, 2013;Dominikowska et al, 2016;Domagała & Palusiak, 2014;Domagała et al, 2017).…”

Supramolecular Covalence in Bifurcated Chalcogen Bonding

“…These formally noncovalent interactions play an important role in determiningt he arrangemento fs upramolecular assemblies and in shaping the structures of various macromolecules, such as proteins and nucleic acids. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Intensive structural investigations in the fields of biopolymers and organic materials have revealed that these less common interactions contributec onsiderably to the stabilization of various molecular conformations. [11][12][13] In recent years, increasing attentionh as been paid to halogen, chalcogen, and pnicogen bonds in various fields of chemistry.…”

“…[11][12][13] In recent years, increasing attentionh as been paid to halogen, chalcogen, and pnicogen bonds in various fields of chemistry. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Intensive structural investigations in the fields of biopolymers and organic materials have revealed that these less common interactions contributec onsiderably to the stabilization of various molecular conformations. [32,33] However, there hasb een al ong-term discussion about the nature of these interactions and the relative roles of electrostatics, [34,35] Pauli repulsion, [36,37] dispersion, [38] and charget ransfer (CT).…”

Could Quantum Mechanical Properties Be Reflected on Classical Molecular Dynamics? The Case of Halogenated Organic Compounds of Biological Interest

“…On one hand, some researchers address the origin of the XBs to the existence of a positive electrostatic potential region on the halogen atom (X) bond called σ-hole (Clark et al, 2007;Politzer et al, 2007Politzer et al, , 2013Kolár et al, 2014). On the other hand, the literature also highlights the importance of the orbital interactions, revealing the covalency part of XB (Wolters and Bickelhaupt, 2012;Wang et al, 2014;Novák et al, 2015;Wolters et al, 2015;Dominikowska et al, 2016;Bora et al, 2017;Santos et al, 2017). In contrast to molecular mechanics approaches, the XB are purely quantum chemical phenomena, whose strength grows with the size of the halogens, making chlorine, bromine, and iodine promising alternatives to promote secondary sidechain interactions inside protein cavities (Lu et al, 2010;Cavallo et al, 2016;Santos et al, 2017).…”