Original paper

Journal of Molecular Modeling

, Volume 13, Issue 2, pp 305-311

First online:

An overview of halogen bonding

  • Peter PolitzerAffiliated withDepartment of Chemistry, University of New Orleans Email author 
  • , Pat LaneAffiliated withDepartment of Chemistry, University of New Orleans
  • , Monica C. ConchaAffiliated withDepartment of Chemistry, University of New Orleans
  • , Yuguang MaAffiliated withDepartment of Chemistry, Wake Forest University
  • , Jane S. MurrayAffiliated withDepartment of Chemistry, University of New Orleans

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Halogen bonding (XB) is a type of noncovalent interaction between a halogen atom X in one molecule and a negative site in another. X can be chlorine, bromine or iodine. The strength of the interaction increases in the order Cl<Br<I. After a brief review of experimental evidence relating to halogen bonding, we present an explanation for its occurrence in terms of a region of positive electrostatic potential that is present on the outermost portions of some covalently-bonded halogen atoms. The existence and magnitude of this positive region, which we call the σ-hole, depends upon the relative electron-attracting powers of X and the remainder of its molecule, as well as the degree of sp hybridization of the s unshared electrons of X. The high electronegativity of fluorine and its tendency to undergo significant sp hybridization account for its failure to halogen bond. Some computed XB interaction energies are presented and discussed. Mention is also made of the importance of halogen bonding in biological systems and processes, and in crystal engineering.


The computed B3PW91/6-31G(d,p) electrostatic potential, in kcal mol−1, on the 0.001 electrons/bohr3 surface of NC–C≡C–Cl. The chlorine atom is at the right. The color ranges are: red, more positive than 15; yellow between 7 and 15; green, between 0 and 7; blue, between −10 and 0; purple, more positive than −10.


Halogen bonding Noncovalent interactions Molecular electrostatic potentials