Halogen Bonding

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Halogen.png


List of participants[edit]

  1. Carlos Martín Fernández, KU Leuven. Slides
  2. Fonsecaguerra (talk) 16:07, 27 August 2017 (CEST) Slides
  3. Ulrich Wedig, Max Planck Institute for Solid State Research, Stuttgart. Slides

Discussion[edit]

--CarlosMF (talk) 22:23, 13 August 2017 (CEST)The usage of the σ-hole concept to explain the halogen bond has clearly been a great discovery in the past decade(s), and has been used also to rationalize other kinds of weak interactions such as chalcogen, pnictogen, tetrel, aerogen, and all kinds of bonds... However, despite the importance of electrostatics for this interaction, there is much debate in the literature on which other factors are important: charge-transfer, exchange, orbital interactions, polarization, induction... The point I want to address, based mainly on the discussion by Politzer et al.[1][2], is about the "mathematical interpretation" vs. "physical reality" debate, and whether this debate is necessary or not. I will add references soon

--Wedig (talk) 10:08, 29 August 2017 (CEST) Halogen Bonding in Chlorinated Fullerenes: (Slides) Crystals of Fullerenes often show rotational disorder, which hampers the precise determination of the positions of the carbon atoms by X-ray diffraction. Thus the identification of specific isomers is not possible. After chlorination of the Fullerenes, well ordered crystals can be obtained, due to the Cl...Cl interactions. In order to get more insight into these interactions, quantum chemical calculations have been performed on dimers of H3CCl and (C2H3)3CCl, acting as model systems for the substituted Fullerenes.[3] The bonding is caused by dynamical electron correlations, being influenced, however, by the chemical environment and geometrical constraints.

--David L. Cooper: When I first learnt about chemical bonding (admittedly in a different millennium) we heard about hydrogen bonding even in introductory courses. Nowadays, students could also be introduced at an equivalent stage to halogen bonding. What else is there that is of sufficient importance/prevalence that it should reasonably be included in undergraduate ‘general chemistry’ courses?


--93.156.209.234 21:57, 10 December 2017 (CEST)Very good question, which could be expanded to the whole chemical community. I think that within 'general chemistry' concepts that include halogen bond, the idea that same sign formal partial charges does not stop attractive interactions from happening would be an interesting concept to pass on. Halogen bonds are a very good example where total formal charges are not incompatible with 'holes' of different charge. Anion-anion interactions in solids are another example where exchange is favored in spite of a 'real' charge...

--Fonseca Guerra 21:09, 30 December 2017 (CEST) Halogen (X) bonds are similar in nature to hydrogen (H) bonds: both have a sizeable covalent component stemming from HOMO–LUMO interactions between lone pair and anti-bonding σ* LUMO on the H/X-bond accepting and donating moiety, respectively. Neither halogen bonds nor hydrogen bonds are, therefore, predominantly, let alone purely electrostatic phenomena [4][5]. The cooperativity in halogen and hydrogen bonds that occur in cyclic arrangements such as quartets are explained with the covalent component: it originates from the charge separation that goes with donor–acceptor orbital interactions in the σ-electron system [6][7][8]. This has been unambiguously quantified with the deformation density associated with bond formation. A physical interpretation of the results is accomplished using the Kohn–Sham MO theory, supported by a quantitative interaction energy decomposition scheme.


Relevant references[edit]

  1. Politzer, P.; Murray, J. S.; Clark, T. Mathematical modeling and physical reality in noncovalent interactions J Mol. Model. 2015 21: 52', DOI:10.1007/s00894-015-2585-5
  2. Politzer, P.; Riley, K. E.; Bulat, F. A.; Murray, J. S. Perspectives on halogen bonding and other σ-hole interactions: Lex parsimoniae (Occam's Razor) Comp. Theor. Chem, 2012, 998, 2-8 DOI:10.1016/j.comptc.2012.06.007
  3. Wedig, U.; Amsharov, K. Yu.; Jansen, M. Z. Anorg. Allg. Chem, 2012, 638, 1625. DOI:10.1002/zaac.201204117
  4. C. Fonseca Guerra; F. M. Bickelhaupt Angew. Chem. Int. Ed.,1999, 38, 2942 – 2945.
  5. L. P. Wolters; F. M. Bickelhaupt, ChemistryOpen, 2012, 1, 96 – 10
  6. C. Fonseca Guerra; H. Zijlstra; Gábor Paragi; F. M. Bickelhaupt, Chem. Eur. J., 2011, 17, 12612 – 12622
  7. L. P. Wolters; N. W. G. Smits; C. Fonseca Guerra, Phys. Chem. Chem. Phys., 2015, 17, 1585 – 1592
  8. G. Paragi; C. Fonseca Guerra; Chem. Eur. J., 2017, 23, 3042 – 3050