Halogen-bonded adduct of 1,2-dibromo-1,1,2,2-tetrafluoroethane and 1,4-diazabicyclo[2.2.2]octane

Halogen bonding is a well-established and intensively studied intermolecular interaction that has also been used in the preparation of functional materials. While polyfluoroiodo- and polyfluorobromobenzenes have been widely used as aromatic halogen-bond donors, there have been very few studies of iodoimidazoles with regard to halogen bonding. We describe here the X-ray structures of three iodoimidazole derivatives, namely 1-benzyl-2-iodo-1H-imidazole, C10H9IN2, (1), 1-benzyl-4-iodo-1H-imidazole, C10H9IN2, (2), and 1-benzyl-2-iodo-1H-benzimidazole, C14H11IN2, (3), and the halogen bonds that dominate the intermolecular interactions in each of these three structures. The three-dimensional structure of (1) is dominated by a strong C—I...N halogen bond, with an N...I distance of 2.8765 (2) Å, that connects the molecules into one-dimensional zigzag ribbons of molecules. In contrast, the three-dimensional structures of (2) and (3) both feature C—I...π halogen-bonded dimers.

Download Full-text

Halogen bonding in a series of Br(CF2) n Br–DABCO adducts (n = 4, 6, 8)

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229617013663 ◽

2017 ◽

Vol 73 (11) ◽

pp. 874-879 ◽

Cited By ~ 1

Author(s):

Alan K. Brisdon ◽

Abeer M. T. Muneer ◽

Robin G. Pritchard

Keyword(s):

Solid Phase ◽

Halogen Bond ◽

Van Der Waals ◽

Halogen Bonding ◽

Vapour Phase ◽

X Ray Diffraction ◽

Nitrogen Base ◽

One Dimensional ◽

X Ray ◽

Van Der Waals Radii

Halogen bonding (XB) is a highly-directional class of intermolecular interactions that has been used as a powerful tool to drive the design of crystals in the solid phase. To date, the majority of XB donors have been iodine-containing compounds, with many fewer involving brominated analogues. We report the formation of adducts in the vapour phase from a series of dibromoperfluoroalkyl compounds, BrCF2(CF2) n CF2Br (n = 2, 4, 6), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Single-crystal X-ray diffraction studies of the colourless crystals identified 1,4-diazabicyclo[2.2.2]octane–1,4-dibromoperfluorobutane (1/1), C4Br2F8·C6H12N2, (I), 1,4-diazabicyclo[2.2.2]octane–1,6-dibromoperfluorohexane (1/1), C6Br2F12·C6H12N2, (II), and 1,4-diazabicyclo[2.2.2]octane–1,8-dibromoperfluorooctane (1/1), C8Br2F16·C6H12N2, (III), each of which displays a one-dimensional halogen-bonded network. All three adducts exhibit N...Br distances less than the sum of the van der Waals radii, with butane analogue (I) showing the shortest N...Br halogen-bond distances yet reported between a bromoperfluorocarbon and a nitrogen base [2.809 (3) and 2.818 (3) Å], which are 0.58 and 0.59 Å shorter than the sum of the van der Waals radii.

Download Full-text

Applications of halogen bonding in solution

Pure and Applied Chemistry ◽

10.1515/pac-2014-0807 ◽

2015 ◽

Vol 87 (1) ◽

pp. 15-41 ◽

Cited By ~ 39

Author(s):

Andreas Vargas Jentzsch

Keyword(s):

Halogen Atom ◽

Halogen Bond ◽

Halogen Bonding ◽

Solvent System ◽

Noncovalent Interaction ◽

Solution Phase ◽

Anion Binding ◽

Lewis Bases ◽

The Past ◽

Catalytic Applications

AbstractHalogen bonding is the noncovalent interaction where the halogen atom acts as an electrophile towards Lewis bases. Known for more than 200 years, only recently it has attracted interest in the context of solution-phase applications, especially during the last decade which was marked by the introduction of multitopic systems. In addition, the small yet rich collection of halogen-bond donor moieties that appeared in this period is shown to be versatile enough as to be applied in virtually any solvent system. This review covers the applications of halogen bonding in solution during the past ten years in a semi-comprehensive way. Emphasis is made on molecular recognition, catalytic applications and anion binding and transport. Medicinal applications are addressed as well with key examples. Focussing on the major differences observed for halogen bonding, as compared to the ubiquitous hydrogen bonding, it aims to contribute to the design of future solution-phase applications.

Download Full-text

The15N NMR chemical shift in the characterization of weak halogen bonding in solution

Faraday Discussions ◽

10.1039/c7fd00107j ◽

2017 ◽

Vol 203 ◽

pp. 333-346 ◽

Cited By ~ 11

Author(s):

Sebastiaan B. Hakkert ◽

Jürgen Gräfenstein ◽

Mate Erdelyi

Keyword(s):

Hydrogen Bond ◽

Chemical Shift ◽

Halogen Bond ◽

Molar Fraction ◽

Halogen Bonding ◽

Relative Strength ◽

Lewis Base ◽

Halogen Bonds ◽

Bonded Complexes

We have studied the applicability of15N NMR spectroscopy in the characterization of the very weak halogen bonds of nonfluorinated halogen bond donors with a nitrogenous Lewis base in solution. The ability of the technique to detect the relative strength of iodine-, bromine- and chlorine-centered halogen bonds, as well as solvent and substituent effects was evaluated. Whereas computations on the DFT level indicate that15N NMR chemical shifts reflect the diamagnetic deshielding associated with the formation of a weak halogen bond, the experimentally observed chemical shift differences were on the edge of detectability due to the low molar fraction of halogen-bonded complexes in solution. The formation of the analogous yet stronger hydrogen bond of phenols have induced approximately ten times larger chemical shift changes, and could be detected and correlated to the electronic properties of substituents of the hydrogen bond donors. Overall,15N NMR is shown to be a suitable tool for the characterization of comparably strong secondary interactions in solution, but not sufficiently accurate for the detection of the formation of thermodynamically labile, weak halogen bonded complexes.

Download Full-text

Catalytic Activation via π –Backbonding in Halogen Bonds?

10.26434/chemrxiv.13253918 ◽

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.

Download Full-text

Anion Templated Crystal Engineering of Halogen Bonding Tripodal Tris(halopyridinium) Compounds

10.26434/chemrxiv.11862900.v1 ◽

2020 ◽

Author(s):

Emer Foyle ◽

Nicholas White

Keyword(s):

Crystal Engineering ◽

Self Assembly ◽

Halogen Bond ◽

Halogen Bonding ◽

Halogen Bonds ◽

X Ray ◽

X Ray Crystallography ◽

H Nmr ◽

Structural Database ◽

Van Der Waals Radii

<div>In this work four new tripodal tris(halopyridinium) receptors containing potentially halogen</div><div>bonding groups were prepared. The ability of the receptors to bind anions in competitive</div><div>CD<sub>3</sub>CN/d<sub>6</sub>-DMSO was studied using <sup>1</sup>H NMR titration experiments, which revealed that the</div><div>receptors bind chloride anions more strongly than more basic acetate or other halide ions.</div><div>The solid state self–assembly of the tripodal receptors with halide anions was investigated by</div><div>X-ray crystallography. The nature of the structures was dependent on the choice of halide</div><div>anion, as well as the crystallisation solvent. Halogen bond lengths as short as 80% of the sum</div><div>of the van der Waals radii were observed, which is shorter than any halogen bonds involving</div><div>halopyridinium receptors in the Cambridge Structural Database.</div>

Download Full-text

Anion Templated Crystal Engineering of Halogen Bonding Tripodal Tris(halopyridinium) Compounds

10.26434/chemrxiv.11862900 ◽

2020 ◽

Author(s):

Emer Foyle ◽

Nicholas White

Keyword(s):

Crystal Engineering ◽

Self Assembly ◽

Halogen Bond ◽

Halogen Bonding ◽

Halogen Bonds ◽

X Ray ◽

X Ray Crystallography ◽

H Nmr ◽

Structural Database ◽

Van Der Waals Radii

<div>In this work four new tripodal tris(halopyridinium) receptors containing potentially halogen</div><div>bonding groups were prepared. The ability of the receptors to bind anions in competitive</div><div>CD<sub>3</sub>CN/d<sub>6</sub>-DMSO was studied using <sup>1</sup>H NMR titration experiments, which revealed that the</div><div>receptors bind chloride anions more strongly than more basic acetate or other halide ions.</div><div>The solid state self–assembly of the tripodal receptors with halide anions was investigated by</div><div>X-ray crystallography. The nature of the structures was dependent on the choice of halide</div><div>anion, as well as the crystallisation solvent. Halogen bond lengths as short as 80% of the sum</div><div>of the van der Waals radii were observed, which is shorter than any halogen bonds involving</div><div>halopyridinium receptors in the Cambridge Structural Database.</div>

Download Full-text

Halogen Bonding: A Halogen-Centered Noncovalent Interaction Yet to Be Understood

Inorganics ◽

10.3390/inorganics7030040 ◽

2019 ◽

Vol 7 (3) ◽

pp. 40 ◽

Cited By ~ 37

Author(s):

Pradeep Varadwaj ◽

Arpita Varadwaj ◽

Helder Marques

Keyword(s):

Electron Density ◽

Weak Interactions ◽

Early Recognition ◽

Noncovalent Interactions ◽

Covalent Bond ◽

Halogen Bonding ◽

Noncovalent Interaction ◽

Type I ◽

Type Ii ◽

Halogen Bonds

In addition to the underlying basic concepts and early recognition of halogen bonding, this paper reviews the conflicting views that consistently appear in the area of noncovalent interactions and the ability of covalently bonded halogen atoms in molecules to participate in noncovalent interactions that contribute to packing in the solid-state. It may be relatively straightforward to identify Type-II halogen bonding between atoms using the conceptual framework of σ-hole theory, especially when the interaction is linear and is formed between the axial positive region (σ-hole) on the halogen in one monomer and a negative site on a second interacting monomer. A σ-hole is an electron density deficient region on the halogen atom X opposite to the R–X covalent bond, where R is the remainder part of the molecule. However, it is not trivial to do so when secondary interactions are involved as the directionality of the interaction is significantly affected. We show, by providing some specific examples, that halogen bonds do not always follow the strict Type-II topology, and the occurrence of Type-I and -III halogen-centered contacts in crystals is very difficult to predict. In many instances, Type-I halogen-centered contacts appear simultaneously with Type-II halogen bonds. We employed the Independent Gradient Model, a recently proposed electron density approach for probing strong and weak interactions in molecular domains, to show that this is a very useful tool in unraveling the chemistry of halogen-assisted noncovalent interactions, especially in the weak bonding regime. Wherever possible, we have attempted to connect some of these results with those reported previously. Though useful for studying interactions of reasonable strength, IUPAC’s proposed “less than the sum of the van der Waals radii” criterion should not always be assumed as a necessary and sufficient feature to reveal weakly bound interactions, since in many crystals the attractive interaction happens to occur between the midpoint of a bond, or the junction region, and a positive or negative site.

Download Full-text

Halogen…π Interactions in the Complexes of Fluorenonophane With Haloforms

10.21203/rs.3.rs-747526/v1 ◽

2021 ◽

Author(s):

Svitlana V. Shishkina ◽

Viktoriya V. Dyakonenko ◽

Oleg V. Shishkin ◽

Volodimir P. Semynozhenko ◽

Tatiana Yu. Bogashchenko ◽

...

Keyword(s):

Halogen Atom ◽

Halogen Bond ◽

Bromine Atom ◽

Quantum Chemical Study ◽

Halogen Bonding ◽

Chemical Study ◽

Interaction Energies ◽

Halogen Bonds ◽

Guest Molecules ◽

True Energy

Abstract The study of two complexes of fluorenonophane with CHCl3 and CHBr3 molecules has revealed that they differ mainly by the halogen bonds between host and guest molecules. The experimental and theoretical quantum chemical study has shown that the strength of a halogen bond depends on the nature of a halogen atom as well as its orientation to the π-system. The more positive electrostatic potential was revealed at the bromine atom indicating the stronger halogen bond with its participation that was confirmed by the interaction energies calculated for corresponding dimers and the evaluation of the true energy of a halogen bond. The orientation of the chlorine atom at the carbon aromatic atom instead of the center of the benzene ring leads to the shortest Hal…C distance that points out the stronger interaction according to the geometrical characteristics. The EDA analysis of the fluorenonophane complexes with CHCl3 and CHBr3 and their analogs with one halogen atom replaced by the hydrogen atom allows us to presume that the nature of halogen bonding is rather dispersive than electrostatic.

Download Full-text

Catalytic Activation via π –Backbonding in Halogen Bonds?

10.26434/chemrxiv.13253918.v1 ◽

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.

Download Full-text