Spectroscopic Measurement of a Halogen Bond Energy Zhang, Xinxing; Liu, Gaoxiang; Ciborowski, Sandra ...
Angewandte Chemie International Edition,
August 12, 2019, Letnik:
58, Številka:
33
Journal Article
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Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen ...bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br− anions is reported. The XB strength between the positively‐charged σ‐hole on the Br atom of the bromotrichloromethane (CCl3Br) molecule and the Br− anion was found to be 0.63 eV (14.5 kcal mol−1). In the neutral complexes, Br(CCl3Br)1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl3Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol−1) and 0.12 eV (2.8 kcal mol−1).
Strong noncovalent interaction: While halogen bonding has been widely recognized in many fields of chemistry, a benchmark spectroscopic measurement of its strength is still absent. Here, the strength of a poster child halogen bond between Br− and CCl3Br using anion photoelectron spectroscopy is reported.
Synthesis and structural characterization of binary co-crystals 1–4 is reported in the present paper. Selenourea and 1,1-dimethylselenourea were used as selenium-containing halogen bond (XB) ...acceptors and iodopentafluorobenzene (IPFB), 1,4-diiodotetrafluorobenzene (1,4-DIFB) and 1,4-dibromotetrafluorobenzene (1,4-DBrFB) as XB donors. A comparative analysis of the similar binary co-crystals of selenourea and thiourea with a halogen donor revealed that Se … Hal halogen bonds are up to 13.12% shorter than the sum of vdW radii, while in case of S … Hal halogen bonds this value is 11.4%. Therefore, selenium tends to form stronger bonds with halogens than sulfur does. Comparisons of XB interaction energies, Hirschfeld and QTAIM analyses of the Se and S systems supported this observation that selenium based XB acceptor results in slightly stronger Ch⋅⋅⋅Hal halogen bonding.
Halogen bonding (XB) between selenium and halogen atoms has been investigated in a series of binary co-crystals, consisting of selenoureas and fluorinated organohalides. Display omitted
•Binary co-crystals of selenoureas and fluorinated organohalides were synthesized and structurally characterized.•Selenium atoms exhibit XB acceptor properties upon interaction with halogens.•Comparative analysis of Se⋅⋅⋅Hal and S⋅⋅⋅Hal interactions in similar adducts has been conducted.•Possible biological importance of selenourea can be expected due its similarity to a well-known antithyroid-active thiourea.
In this article, a new type of halogen-bonded complex YCCX···HMY (X = Cl, Br; M = Be, Mg; Y = H, F, CH₃) has been predicted and characterized at the MP2/aug-cc-pVTZ level. We named it as ...halogen-hydride halogen bonding. In each YCCX···HMY complex, a halogen bond is formed between the positively charged X atom and the negatively charged H atom. This new kind of halogen bond has similar characteristics to the conventional halogen bond, such as the elongation of the C---X bond and the red shift of the C---X stretch frequency upon complexation. The interaction strength of this type of halogen bond is in a range of 3.34-10.52 kJ/mol, which is smaller than that of dihydrogen bond and conventional halogen bond. The nature of the electrostatic interaction in this type of halogen bond has also been unveiled by means of the natural bond orbital, atoms in molecules, and energy decomposition analyses.
Due to their high electron density, fluoride anions can be considered the most effective halogen bond (HaB) acceptors among the halides. However, under common experimental conditions, F− uncommonly ...acts as HaB acceptor, expectedly as it is present in hydrated form. Herein we report that under specific crystallization conditions a hydrogen bond‐free F− functioning as donor of electron density can be obtained, with the formed HaBs constituting the driving force of the observed crystal packings. Computations confirm the strength of these HaBs compared to analogous interactions involving other halides.
Fluoride anions are excellent donors of electron density, namely halogen bond acceptors, although they are hardly available due to their high propensity to form hydrogen bonds. Herein we report how a proper design of the experimental conditions can lead to promote unlikely noncovalent interactions as a driving force in the solid‐state packing.
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•Anions can engage in strong noncovalent bonds.•These bonds can include halogen, chalcogen, pnicogen, and tetrel, as well as H-bonds.•The coordination around each anion can vary with ...the type of bond and number of ligands.
Research on σ-hole interactions that include halogen, chalcogen, pnicogen, and tetrel bonding has been accelerating in recent years. These cousins of the H-bond have many similar properties, including geometric preferences and energetics. Most of the work to date has focused on neutral complexes, with less known about these bonds to anions. This review summarizes the current state of knowledge about the complexes of anions with ligands that engage in these sorts of noncovalent bonds. Of particular interest are comparisons with H-bonds, and how the geometry of the fully coordinated complex varies as the number of surrounding ligands increases. A specific application of these ideas is explored in which these noncovalent bonds can be used to selectively bind certain anions in a multidentate arrangement, where a symbiotic interplay of experimental and computational methods has provided some useful insights.
Halothane, a commonly used anesthetic can simultaneously function as a hydrogen‐bond and a halogen‐bond donor in the solid state and in solution, as shown by S. V. Rosokha, G. Resnati, and co‐workers ...in their Communication on page 12456 ff. Both interactions involve moieties commonly present in cell membranes, probable target structures of halothane in the human body. The ability of the agent to act as a polydentate tecton gives a molecular rationale for its eudismic ratio.
Can we tune the physicochemical properties of free‐standing organic membranes without changing the building blocks or post‐synthetic modifications? The Research Article (e202200905) by Dinesh Shetty ...et al. demonstrates a novel pre‐synthetically controlled framework growth strategy to tune the hydrophobicity of 3D‐Covalent Organic Framework (3D‐COF) membranes. The hydrophobic 3D‐COF membrane shows potential use for the demulsification of an oil–water mixture, a significant environmental and water reuse issue.
A three‐center halogen bond modulates the reactivity of a halonium ion and is thereby applicable for controlling the halogenation of alkenes. Chelation, strain, steric hindrance, and electrostatic ...interactions influence the halonium release rate. Combined experimental and theoretical analysis of the reaction mechanism highlights the impact of secondary interactions, and is expected to provide a handle on the induction of stereoselectivity in electrophilic halogenation. More information can be found in the Full Paper by I. Pápai, N. Bowling, M. Erdelyi et al. (DOI: 10.1002/chem.202102575).
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