Effect of substitution on the bonding in He dimer confined within dodecahedrane: A computational study.

The effect of substitution in the dodecahedrane (C20 H20 ) cage on bonding in the confined He dimer is analyzed. The HeHe distances inside the halogenated dodecahedrane C20 X20 (X = FBr) cages are found to be less than half of that in the free He dimer. Comparing the equilibrium structure of He2 @C20 H20 with He2 @C20 X20 at ωB97XD/def2-TZVPP level, it is found that the He-He distances are relatively larger in the latter cases indicating the influence of halogen groups on the interaction between the cage and the trapped He pair. The viability of the He2 @C20 X20 complexes is reflected in the presence of a very high activation energy barrier against the thermochemically feasible dissociation process producing free He2 and C20 X20 . Quantum theory of atoms in molecules (QTAIM) approach reveals a partial covalent interaction between He pair.