scholarly journals Experimental investigation of halogen-bond hard–soft acid–base complementarity

2017 ◽  
Vol 73 (2) ◽  
pp. 203-209 ◽  
Author(s):  
Asia Marie S. Riel ◽  
Morly J. Jessop ◽  
Daniel A. Decato ◽  
Casey J. Massena ◽  
Vinicius R. Nascimento ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Halogen Bond ◽  
Noncovalent Interaction ◽  
Computational Studies ◽  
Donor Atom ◽  
Acid Base ◽  
State Data ◽  
Lewis Bases ◽  
Soft Acid ◽  
Solution Speciation

The halogen bond (XB) is a topical noncovalent interaction of rapidly increasing importance. The XB employs a `soft' donor atom in comparison to the `hard' proton of the hydrogen bond (HB). This difference has led to the hypothesis that XBs can form more favorable interactions with `soft' bases than HBs. While computational studies have supported this suggestion, solution and solid-state data are lacking. Here, XB soft–soft complementarity is investigated with a bidentate receptor that shows similar associations with neutral carbonyls and heavy chalcogen analogs. The solution speciation and XB soft–soft complementarity is supported by four crystal structures containing neutral and anionic soft Lewis bases.

Bidentate Chiral Bis(imidazolium)-Based Halogen Bond Donors: Synthesis and First Applications in Enantioselective Recognition and Catalysis

2019 ◽  
Author(s):  
Revannath L. Sutar ◽  
Elric Engelage ◽  
Raphael Stoll ◽  
Stefan Huber
Keyword(s):  
Lewis Acids ◽  
Chiral Recognition ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Noncovalent Interaction ◽  
Asymmetric Induction ◽  
Nmr Studies ◽  
Lewis Bases ◽  
First Case ◽  
Mukaiyama Aldol

Even though halogen bonding – the noncovalent interaction between electrophilic halogen substituents and Lewis bases – has now been established in molecular recognition and catalysis, its use in enantioselective processes is still very little explored. Herein, we present the synthesis of chiral bidentate halogen bond donors based on two iodoimidazolium units with rigidly attached chiral sidearms. With these Lewis acids, chiral recognition of a racemic diamine is achieved in NMR studies. DFT calculations support a 1:1 interaction of the halogen bond donor with both enantiomers and indicate that the chiral recognition is based on a different spatial orientation of the Lewis bases in the halogen bonded complexes. In addition, moderate enantioselectivity is achieved in a Mukaiyama aldol reaction with a preorganized variant of the chiral halogen bond donor. This represents the first case in which asymmetric induction was realized with a pure halogen bond donor lacking any additionally active functional groups.

Applications of halogen bonding in solution

2015 ◽  
Vol 87 (1) ◽  
pp. 15-41 ◽  
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.

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.

Bidentate Chiral Bis(imidazolium)-Based Halogen Bond Donors: Synthesis and First Applications in Enantioselective Recognition and Catalysis

2019 ◽  
Author(s):  
Revannath L. Sutar ◽  
Elric Engelage ◽  
Raphael Stoll ◽  
Stefan Huber
Keyword(s):  
Lewis Acids ◽  
Chiral Recognition ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Noncovalent Interaction ◽  
Asymmetric Induction ◽  
Nmr Studies ◽  
Lewis Bases ◽  
First Case ◽  
Mukaiyama Aldol

Even though halogen bonding – the noncovalent interaction between electrophilic halogen substituents and Lewis bases – has now been established in molecular recognition and catalysis, its use in enantioselective processes is still very little explored. Herein, we present the synthesis of chiral bidentate halogen bond donors based on two iodoimidazolium units with rigidly attached chiral sidearms. With these Lewis acids, chiral recognition of a racemic diamine is achieved in NMR studies. DFT calculations support a 1:1 interaction of the halogen bond donor with both enantiomers and indicate that the chiral recognition is based on a different spatial orientation of the Lewis bases in the halogen bonded complexes. In addition, moderate enantioselectivity is achieved in a Mukaiyama aldol reaction with a preorganized variant of the chiral halogen bond donor. This represents the first case in which asymmetric induction was realized with a pure halogen bond donor lacking any additionally active functional groups.

Application of hard and soft acid base theory to uncover Lewis bases’ destructiveness to UiO-66 type metal organic frameworks in aqueous solutions

2021 ◽  
Author(s):  
Liangjie Wang ◽  
Juan Li ◽  
Luyao Cheng ◽  
Yonghui Song ◽  
Ping Zeng ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Aqueous Solutions ◽  
Metal Organic Frameworks ◽  
Acid Base ◽  
Lewis Bases ◽  
Base Theory ◽  
Metal Organic ◽  
The Stability ◽  
Soft Acid

Lewis bases (L-bases) in wastewater, such as F- and PO43-, are destructive to the stability of MOFs which have attracted increasing attentions in wastewater treatment field as adsorbents and catalysts....

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.

An analysis of the factors contributing to the regioselectivity observed in the opening of oxiranes

1980 ◽  
Vol 58 (3) ◽  
pp. 302-306 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Oxygen Atom ◽  
Ring Opening ◽  
Oxirane Ring ◽  
Epoxide Ring ◽  
Acid Base ◽  
Epoxide Ring Opening ◽  
Soft Acid ◽  
Hsab Theory

The regioselectivity of epoxide ring opening can be analyzed in terms of hard–soft acid–base (HSAB) theory. The coordination of the hard acid with the oxygen atom of the oxirane ring produces a "pulling effect" which determines the direction of the ring opening. In the absence of a strong "pulling effect" the "pushing effect" of the approaching base is examined and the consequences of relative softness or hardness of the nucleophile on the regioselectivity of the ring opening are discussed.

The role of the Lewis acid−base properties in the supramolecular association of 1,2,5-chalcogenadiazoles

2013 ◽  
Vol 91 (5) ◽  
pp. 338-347 ◽  
Author(s):  
Anthony F. Cozzolino ◽  
Philip J.W. Elder ◽  
Lucia Myongwon Lee ◽  
Ignacio Vargas-Baca
Keyword(s):  
Topological Analysis ◽  
Structural Features ◽  
Lewis Acidity ◽  
Electron Localization ◽  
Dispersion Forces ◽  
Acid Base ◽  
Lewis Bases ◽  
The Individual ◽  
Secondary Bonding

The secondary bonding interactions that link the supramolecular structures assembled by 1,2,5-chalcogenadiazoles were analyzed through explicit orthogonalization of molecular orbitals (NBO), topological analysis of the electron density (AIM), and the electron localization function (ELF). The results of these analyses are consistent with a bonding description that attributes important covalent and electrostatic character to these interactions. Application of these analyses to the individual molecules highlighted the structural features from which each of those contributions originates, namely the polarity and modest strength of the E–N bond. Both of these effects increase along the series S, Se, Te. Perturbations to the heterocycle electronic structure that result in a weaker and more polar E–N bond cause an increase in the Lewis acidity at the chalcogen centre, which in turn leads to stronger secondary bonding interactions with Lewis bases. Additionally, the contribution of dispersion forces is not negligible and is most important in the case of sulfur.

scholarly journals Imparting gas selective and pressure dependent porosity into a non-porous solid via coordination flexibility

2019 ◽  
Vol 6 (9) ◽  
pp. 1883-1891 ◽  
Author(s):  
Shyamapada Nandi ◽  
Phil De Luna ◽  
Rahul Maity ◽  
Debanjan Chakraborty ◽  
Thomas Daff ◽  
...  
Keyword(s):  
Porous Solid ◽  
Acid Base ◽  
Base Concept ◽  
Soft Acid

Using a simple hard–soft acid–base concept we have deliberately designed gas-specific and pressure dependent porosity into a non-porous solid via coordination flexibility.

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