scholarly journals An expanded halogen bonding scale using astatine

2021 ◽  
Author(s):  
Lu Liu ◽  
Seyfeddine Rahali ◽  
Rémi Maurice ◽  
Cecilia Gomez Pech ◽  
Gilles Montavon ◽  
...  
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Pivotal Role ◽  
Covalent Interaction ◽  
Intermolecular Recognition

As a non-covalent interaction, halogen bonding is now acknowledged to be useful in all fields where the control of intermolecular recognition plays a pivotal role. Halogen-bond basicity scales allow to...

1,3,5-Tri(iodoethynyl)-2,4,6-trifluorobenzene: halogen-bonded frameworks and NMR spectroscopic analysis

2017 ◽  
Vol 73 (2) ◽  
pp. 153-162 ◽  
Author(s):  
Patrick M. J. Szell ◽  
Bulat Gabidullin ◽  
David L. Bryce
Keyword(s):  
Solid State ◽  
Crystal Engineering ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Lewis Base ◽  
Phosphonium Salts ◽  
Covalent Interaction ◽  
Framework Materials ◽  
Engineering Strategy ◽  
Triphenylphosphonium Bromide

Halogen bonding is the non-covalent interaction between the region of positive electrostatic potential associated with a covalently bonded halogen atom, named the σ-hole, and a Lewis base. Single-crystal X-ray diffraction structures are reported for a series of seven halogen-bonded cocrystals featuring 1,3,5-tris(iodoethynyl)-2,4,6-trifluorobenzene (1) as the halogen-bond donor, and bromide ions (as ammonium or phosphonium salts) as the halogen-bond acceptors: (1)·MePh3PBr, (1)·EtPh3PBr, (1)·acetonyl-Ph3PBr, (1)·Ph4PBr, (1)·[bis(4-fluorophenyl)methyl]triphenylphosphonium bromide, and two new polymorphs of (1)·Et3BuNBr. The cocrystals all feature moderately strong iodine–bromide halogen bonds. The crystal structure of pure [bis(4-fluorophenyl)methyl]triphenylphosphonium bromide is also reported. The results of a crystal engineering strategy of varying the size of the counter-cation are explored, and the features of the resulting framework materials are discussed. Given the potential utility of (1) in future crystal engineering applications, detailed NMR analyses (in solution and in the solid state) of this halogen-bond donor are also presented. In solution, complex13C and19F multiplets are explained by considering the delicate interplay between variousJcouplings and subtle isotope shifts. In the solid state, the formation of (1)·Et3BuNBr is shown through significant13C chemical shift changes relative to pure solid 1,3,5-tris(iodoethynyl)-2,4,6-trifluorobenzene.

scholarly journals Azobenzene-based difunctional halogen-bond donor: towards the engineering of photoresponsive co-crystals

2013 ◽  
Vol 70 (1) ◽  
pp. 149-156 ◽  
Author(s):  
Marco Saccone ◽  
Giancarlo Terraneo ◽  
Tullio Pilati ◽  
Gabriella Cavallo ◽  
Arri Priimagi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
X Ray Diffraction ◽  
Donor Molecule ◽  
X Ray ◽  
Covalent Interaction ◽  
Material Systems ◽  
Azo Group ◽  
Insight Into

Halogen bonding is emerging as a powerful non-covalent interaction in the context of supramolecular photoresponsive materials design, particularly due to its high directionality. In order to obtain further insight into the solid-state features of halogen-bonded photoactive molecules, three halogen-bonded co-crystals containing an azobenzene-based difunctional halogen-bond donor molecule, (E)-bis(4-iodo-2,3,5,6-tetrafluorophenyl)diazene, C12F8I2N2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal structure of the non-iodinated homologue (E)-bis(2,3,5,6-tetrafluorophenyl)diazene, C12H2F8N2, is also reported. It is demonstrated that the studied halogen-bond donor molecule is a reliable tecton for assembling halogen-bonded co-crystals with potential photoresponsive behaviour. The azo group is not involved in any specific intermolecular interactions in any of the co-crystals studied, which is an interesting feature in the context of enhanced photoisomerization behaviour and photoactive properties of the material systems.

scholarly journals Catalytic Activation via π –Backbonding in Halogen Bonds?

2020 ◽  
Author(s):  
Andrew Wang ◽  
Pierre Kennepohl
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Lewis Base ◽  
Computational Studies ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Bases ◽  
Chemical Catalysis ◽  
Catalytic Activation

The role of halogen bonding (XB) in chemical catalysis has largely involved using XB donors as Lewis acid activators to modulate the reactivity of partner Lewis bases. We explore a more uncommon scenario, where a Lewis base modulates reactivity via a spectator halogen bond interaction. Our computational studies reveal that spectator halogen bonds may play an important role in modulating the rate of S<sub>N</sub>2 reactions. Most notably, π acceptors such as PF<sub>3</sub> significantly decrease the barrier to subsitution by decreasing electron density in the very electron rich transition state. Such π-backbonding represents an example of a heretofor unexplored situation in halogen bonding: the combination of both s-donation and π-backdonation in this “non-covalent” interaction.

Electron-transfer reactions of halogenated electrophiles: a different look into the nature of halogen bonding

2017 ◽  
Vol 203 ◽  
pp. 315-332 ◽  
Author(s):  
Sergiy V. Rosokha
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Halogen Bond ◽  
Structural Characteristics ◽  
Halogen Bonding ◽  
Outer Sphere ◽  
Ferrocene Derivatives ◽  
Dissociative Electron Transfer ◽  
Covalent Interaction ◽  
Electron Transfer Theory

The rates of oxidation of ferrocene derivatives by brominated molecules R-Br (CBr3CN, CBr4, CBr3NO2, CBr3COCBr3, CBr3CONH2, CBr3F, and CBr3H) were consistent with the predictions of the outer-sphere dissociative electron-transfer theory. The similar redox-reactions of the R-Br electrophiles with the typical halogen-bond acceptors tetramethyl-p-phenylenediamine (TMPD) or iodide were much faster than calculated using the same model. The fast redox-processes in these systems were related to the involvement of the transient halogen-bonded [R-Br, TMPD] or [R-Br, I−] complexes in which barriers for electron transfer were lowered by the strong electronic coupling of reactants. The Mulliken–Hush treatment of the spectral and structural characteristics of the [R-Br, TMPD] or [R-Br, I−] complexes corroborated the values of coupling elements, Hab, of 0.2–0.5 eV implied by the kinetic data. The Natural Bond Orbital analysis of these complexes indicated a noticeable donor/acceptor charge transfer, Δq, of 0.03–0.09 ē. The Hab and Δq values in the [R-Br, TMPD] and [R-Br, I−] complexes (which are similar to those in the traditional charge-transfer associates) indicate significant contribution of charge-transfer (weakly-covalent) interaction to halogen bonding. The decrease of the barrier for electron transfer between the halogen-bonded reactants demonstrated in the current work points out that halogen bonding should be taken into account in the mechanistic analysis of the reactions of halogenated species.

scholarly journals Activation of a Metal-Halogen Bond by Halogen Bonding

2020 ◽  
Author(s):  
Stefan Huber ◽  
Julian Wolf ◽  
Florian Huber ◽  
Nikita Erochok ◽  
Flemming Heinen ◽  
...  
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Gold Catalysis ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Acidic Sites ◽  
Test Reactions ◽  
Acidic Sites ◽  
Elemental Iodine

In recent years, the non-covalent interaction of halogen bonding (XB) has found increasing application in organocatalysis. However, reports of the activation of metal-ligand bonds by XB have so far been limited to a few reactions with elemental iodine or bromine. Herein, we present the activation of metal-halogen bonds by two classes of inert halogen bond donors and the use of the resulting activated complexes in homogenous gold catalysis. The only recently explored class of iodolium derivatives were shown to be effective activators in two test reactions and their activity could be modulated by blocking of the Lewis acidic sites. Bis(benzimidazolium)-based halogen bonding activators provided even more rapid conversion, while the non-iodinated reference compound showed little activity. The role of halogen bonding in the activation of metal-halogen bonds was further investigated by NMR experiments and DFT calculations, which support the mode of activation occurring via halogen bonding.

scholarly journals Activation of a Metal-Halogen Bond by Halogen Bonding

2020 ◽  
Author(s):  
Stefan Huber ◽  
Julian Wolf ◽  
Florian Huber ◽  
Nikita Erochok ◽  
Flemming Heinen ◽  
...  
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Gold Catalysis ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Acidic Sites ◽  
Test Reactions ◽  
Acidic Sites ◽  
Elemental Iodine

In recent years, the non-covalent interaction of halogen bonding (XB) has found increasing application in organocatalysis. However, reports of the activation of metal-ligand bonds by XB have so far been limited to a few reactions with elemental iodine or bromine. Herein, we present the activation of metal-halogen bonds by two classes of inert halogen bond donors and the use of the resulting activated complexes in homogenous gold catalysis. The only recently explored class of iodolium derivatives were shown to be effective activators in two test reactions and their activity could be modulated by blocking of the Lewis acidic sites. Bis(benzimidazolium)-based halogen bonding activators provided even more rapid conversion, while the non-iodinated reference compound showed little activity. The role of halogen bonding in the activation of metal-halogen bonds was further investigated by NMR experiments and DFT calculations, which support the mode of activation occurring via halogen bonding.

scholarly journals Catalytic Activation via π –Backbonding in Halogen Bonds?

2020 ◽  
Author(s):  
Andrew Wang ◽  
Pierre Kennepohl
Keyword(s):  
Halogen Bond ◽  
Halogen Bonding ◽  
Lewis Base ◽  
Computational Studies ◽  
Halogen Bonds ◽  
Covalent Interaction ◽  
Lewis Bases ◽  
Chemical Catalysis ◽  
Catalytic Activation

The role of halogen bonding (XB) in chemical catalysis has largely involved using XB donors as Lewis acid activators to modulate the reactivity of partner Lewis bases. We explore a more uncommon scenario, where a Lewis base modulates reactivity via a spectator halogen bond interaction. Our computational studies reveal that spectator halogen bonds may play an important role in modulating the rate of S<sub>N</sub>2 reactions. Most notably, π acceptors such as PF<sub>3</sub> significantly decrease the barrier to subsitution by decreasing electron density in the very electron rich transition state. Such π-backbonding represents an example of a heretofor unexplored situation in halogen bonding: the combination of both s-donation and π-backdonation in this “non-covalent” interaction.

scholarly journals Adenine as a Halogen Bond Acceptor: A Combined Experimental and DFT Study

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 224 ◽  
Author(s):  
Yannick Roselló ◽  
Mónica Benito ◽  
Elies Molins ◽  
Miquel Barceló-Oliver ◽  
Antonio Frontera
Keyword(s):  
Density Functional ◽  
Halogen Bond ◽  
Lone Pair ◽  
Halogen Bonding ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Adenine Ring ◽  
Bonding Interaction ◽  
Donor Ability ◽  
Adenine Derivative

In this work, we report the cocrystallization of N9-ethyladenine with 1,2,4,5-tetrafluoro-3,6-diiodobenzene (TFDIB), a classical XB donor. As far as our knowledge extends, this is the first cocrystal reported to date where an adenine derivative acts as a halogen bond acceptor. In the solid state, each adenine ring forms two centrosymmetric H-bonded dimers: one using N1···HA6–N6 and the other N7···HB6–N6. Therefore, only N3 is available as a halogen bond acceptor that, indeed, establishes an N···I halogen bonding interaction with TFDIB. The H-bonded dimers and halogen bonds have been investigated via DFT (Density Functional Theory) calculations and the Bader’s Quantum Theory of Atoms In Molecules (QTAIM) method at the B3LYP/6-311+G* level of theory. The influence of H-bonding interactions on the lone pair donor ability of N3 has also been analyzed using the molecular electrostatic potential (MEP) surface calculations.

Cyclic networks of halogen-bonding interactions in molecular self-assemblies: a theoretical N—X...NversusC—X...N investigation

2017 ◽  
Vol 73 (2) ◽  
pp. 179-187
Author(s):  
Ruben D. Parra ◽  
Álvaro Castillo
Keyword(s):  
Electron Density ◽  
Self Assembly ◽  
Metal Ion ◽  
Halogen Atom ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Nbo Analysis ◽  
Binding Energies ◽  
Cyclic Network ◽  
Ability To Drive

The geometries and energetics of molecular self-assembly structures that contain a sequential network of cyclic halogen-bonding interactions are investigated theoretically. The strength of the halogen-bonding interactions is assessed by examining binding energies, electron charge transfer (NBO analysis) and electron density at halogen-bond critical points (AIM theory). Specifically, structural motifs having intramolecular N—X...N (X= Cl, Br, or I) interactions and the ability to drive molecular self-assemblyviathe same type of interactions are used to construct larger self-assemblies of up to three unit motifs. N—X...N halogen-bond cooperativity as a function of the self-assembly size, and the nature of the halogen atom is also examined. The cyclic network of the halogen-bonding interactions provides a suitable cavity rich in electron density (from the halogen atom lone pairs not involved in the halogen bonds) that can potentially bind an electron-deficient species such as a metal ion. This possibility is explored by examining the ability of the N—X...N network to bind Na+. Likewise, molecular self-assembly structures driven by the weaker C—X...N halogen-bonding interactions are investigated and the results compared with those of their N—X...N counterparts.

Cooperative halogen bonding and polarized π-stacking in the formation of coloured charge-transfer co-crystals

2018 ◽  
Vol 42 (13) ◽  
pp. 10615-10622 ◽  
Author(s):  
Chideraa I. Nwachukwu ◽  
Zachary R. Kehoe ◽  
Nathan P. Bowling ◽  
Erin D. Speetzen ◽  
Eric Bosch
Keyword(s):  
Charge Transfer ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Π Stacking

Matched electron rich halogen bond acceptors and donor have been synthesized and the halogen bonded charge transfer cocrystals characterized.

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