skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


This content will become publicly available on February 1, 2026

Title: Halogen Bonding and Rearrangements in Complexes of N-Chlorosuccinimide with Halides
The role of halogen bonding (HaB) in the reactions of N-chlorosuccinimide (SimCl), a versatile reagent in organic synthesis, was investigated through experimental and computational analyses of its interactions with halides. The reactions of SimCl with Br− or I− resulted in the crystallization of HaB complexes of chloride with N-iodosuccinimide (SimI) or N-bromosuccinimide (SimBr). Computational analysis revealed that halogen rearrangements, which occurred even at −73 °C, were facilitated by halogen bonding. The dissociation of SimCl∙Y− (Y = I or Br) complexes into a Sim− + ClY pair (followed by the rotation and re-binding of the interhalogen molecules) bypassed the formation of the high-energy Sim− + Cl+ pair and drastically (about tenfold) reduced the dissociation energy of the N–Cl bond. Furthermore, while the dissociation energy of individual SimCl is higher (and its HaB is weaker) compared to that of SimI or SimBr, the dissociation of the N-Cl bond in SimCl∙Y− requires less energy than in the complexes of SimBr or SimI. The facile cleavage of such bonds in HaB complexes explains the high reactivity of SimCl and its effectiveness as a halogenating agent.  more » « less
Award ID(s):
2404011
PAR ID:
10614324
Author(s) / Creator(s):
; ;
Publisher / Repository:
MDPI
Date Published:
Journal Name:
Molecules
Volume:
30
Issue:
3
ISSN:
1420-3049
Page Range / eLocation ID:
639
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Crystals)
    null (Ed.)
    The wide-range variation of the strength of halogen bonds (XB) not only facilitates a variety of applications of this interaction, but it also allows examining the relation (and interconversion) between supramolecular and covalent bonding. Herein, the Br…Cl halogen bonding in a series of complexes of bromosubstituted electrophiles (R-Br) with chloride anions were examined via X-ray crystallographic and computational methods. Six co-crystals showing such bonding were prepared by evaporation of solutions of R-Br and tetra-n-propylammonium chloride or using Cl− anions released in the nucleophilic reaction of 1,4-diazabicyclo[2.2.2]octane with dichloromethane in the presence of R-Br. The co-crystal comprised networks formed by 3:3 or 2:2 halogen bonding between R-Br and Cl−, with the XB lengths varying from 3.0 Å to 3.25 Å. Analysis of the crystallographic database revealed examples of associations with substantially longer and shorter Br…Cl separations. DFT computations of an extended series of R–Br…Cl− complexes confirmed that the judicious choice of brominated electrophile allows varying halogen Br…Cl bond strength and length gradually from the values common for the weak intermolecular complexes to that approaching a fully developed covalent bond. This continuity of halogen bond strength in the experimental (solid-state) and calculated associations indicates a fundamental link between the covalent and supramolecular bonding. 
    more » « less
  2. ; ; ; (, CrystEngComm)
    The relationship between solid-state supramolecular interactions and crystal habits is highlighted based on experimental and computational analysis of the crystal structure of strong halogen-bonded (HaB) associations between iodine-containing dihalogens (ICl, IBr) with 1,4-diazabicyclo[2,2,2]octane (DABCO) as well as with substituted pyridines and phenazine. The pattern of the energy frameworks and the interplay of the attractive and repulsive interactions in the solid-state associations involving these HaB donors and acceptors directly correlated with their crystal habits. This correlation suggests that analysis of the energy framework serves as a useful tool (complementary to the earlier developed methods) to rationalize and predict the crystal habit. The X-ray structural analysis also revealed that the I⋯N distances in the complexes were in the 2.24–2.54 Å range, i.e. they were much closer to the I⋯N covalent bond length than to the van der Waals separation. The computational analysis of the nature of halogen bonding in these complexes showed delocalization of their molecular orbitals' between donor and acceptors resulting in a substantial charge transfer from the nucleophiles to dihalogens and elongation of the I⋯X bond. As a result, both I⋯N and I⋯X bonds in the strongest complexes ( e.g. , ICl with DABCO or 4-dimethylaminopyridine) are characterized by the comparable Mayer bonds orders of about 0.6, along with the electron and energy densities at their bond critical points of about 0.1 a.u. and −0.02 a.u., respectively. These data as well as the density overlap regions indicator (DORI) point to the covalency of the I⋯N bonding and suggest that the interaction within the IX complexes can be described as (unsymmetrical) hypervalent 3c/4e N⋯I⋯X bonding akin to that in trihalide or halonium ions. 
    more » « less
  3. ; ; (, Beilstein Journal of Organic Chemistry)
    Halogen bonding permeates many areas of chemistry. A wide range of halogen-bond donors including neutral, cationic, monovalent, and hypervalent have been developed and studied. In this work we used density functional theory (DFT), natural bond orbital (NBO) theory, and quantum theory of atoms in molecules (QTAIM) to analyze aryl halogen-bond donors that are neutral, cationic, monovalent and hypervalent and in each series we include the halogens Cl, Br, I, and At. Within this diverse set of halogen-bond donors, we have found trends that relate halogen bond length with the van der Waals radii of the halogen and the non-covalent or partial covalency of the halogen bond. We have also developed a model to calculate ΔGof halogen-bond formation by the linear combination of the % p-orbital character on the halogen and energy of the σ-hole on the halogen-bond donor. 
    more » « less
  4. ; ; ; (, Physical Chemistry Chemical Physics)
    The halogen bond is a class of non-covalent interaction that has attracted considerable attention recently. A widespread theory for describing them is the σ-hole concept, which predicts that the strength of the interaction is proportional to the size of the σ-hole, a region of positive electrostatic potential opposite a σ bond. Previous work shows that in the case of CX 3 I, with X equal to F, Cl, Br, and I, the σ-hole trend is exactly opposite to the trend in binding energy with common electron pair donors. Using energy decomposition analysis (EDA) applied to a potential energy scan as well as the recent adiabatic EDA technique, we show that the observed trend is a result of charge transfer. Therefore a picture of the halogen bond that excludes charge transfer cannot be complete, and permanent and induced electrostatics do not always provide the dominant stabilizing contributions to halogen bonds. Overall, three universally attractive factors, polarization, dispersion and charge transfer, together with permanent electrostatics, which is usually attractive, drive halogen bonding, against Pauli repulsion. 
    more » « less
  5. ; ; ; (, Organic & Biomolecular Chemistry)
    null (Ed.)
    In order to explore how σ-hole potentials, as evaluated by molecular electrostatic potential (MEP) calculations, affect the ability of halogen atoms to engage in structure-directing intermolecular interactions, we synthesized four series of ethynyl halogen-substituted amide containing pyridines (activated targets); ( N -(pyridin-2-yl)benzamides (Bz-act-X), N -(pyridin-2-yl)picolinamides (2act-X), N -(pyridin-2-yl)nicotinamides (3act-X) and N -(pyridin-2-yl) isonicotinamides (4act-X), where X = Cl/Br/I. The molecules are deliberately equipped with three distinctly different halogen-bond acceptor sites, π, N(pyr), and OC, to determine binding site preferences of different halogen-bond donors. Crystallographic data for ten (out of a possible twelve) new compounds were thus analyzed and compared with data for the corresponding unactivated species. The calculated MEPs of all the halogen atoms were higher in the activated targets in comparison to the unactivated targets and were in the order of iodine ≈ chloroethynyl < bromoethynyl < iodoethynyl. This increased positive σ-hole potential led to a subsequent increase in propensity for halogen-bond formation. Two of the four chloroethynyl structures showed halogen bonding, and all three of the structurally characterized bromoethynyl species engaged in halogen bonding. The analogous unactived species showed no halogen bonds. Each chloroethynyl donor selected a π-cloud as acceptor and the bromoethynyl halogen-bond donors opted for either π or N(pyr) sites, whereas all halogen bonds involving an iodoethynyl halogen-bond donor (including both polymorphs of Bz-act-I ) engaged exclusively with a N(pyr) acceptor site. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email