During our studies of Se•••Se interactions in selenides, it was observed that halogen atoms X of C-X bonds were engaged in both a “head-on” and a “side-on” fashion to Se atoms. To understand such interactions, we have analyzed the crystallographic environment around halogen centers and find that, in general, “electrophiles” tend to approach halogens of C-X (X = Cl, Br, I) at an angle of ~ 100° and nucleophiles at ~ 165° and that C—X•••X—C type interactions fall into two groups, one forming an “electrophile-nucleophile pairing” interaction and the other forming no such pairing. These interactions are interpreted in terms of HOMO and LUMO frontier orbitals centered on the halogens and the approaching atoms. Such “electrophile-nucleophile pairing” interactions are quite general for several systems like sulfides and selenides and no doubt are important in the interaction of small molecules containing halogens since halogen atoms often are in a situation to make short contact with a variety of other atoms, owing to their exposed positions in many molecules.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry