Quantification of intramolecular nonbonding interactions in organochalcogens

Intramolecular nonbonding interactions between chalcogen atoms in a series of ortho substituted arylselenides (S/O center dot center dot center dot Se- Y, with Y = -Me, -CN, -Cl, and -F) are quantified using the coupled cluster CCSD(T)/cc-pVDZ level of theory. A homodesmic reaction method as well as an ortho-para approach are employed in evaluating the strength of intramolecular interactions. Comparison of the results obtained using the ab initio MP2 method and pure and hybrid density functional theories are performed with that of the coupled cluster values to assess the quality of different density functionals in evaluating the strength of nonbonding interactions. The interaction energies are found to be higher when the thioformyl group acts as the donor and the Se-F bond acts as the acceptor. In a given series with the same donor atom, the strength of the interaction follows the order Me < CN < Cl < F, exhibiting fairly high sensitivity to the group attached to selenium (Se-Y). Analysis of electron density at the S/O center dot center dot center dot Se bond critical point within the Atoms in Molecule framework shows a very good correlation with the computed intramolecular interaction energies.