Noncovalent Sulfoxide-Nitrile Coupling Involving Four-Center Heteroleptic Dipole-Dipole Interactions between the Sulfinyl and Nitrile Groups

The 4-X-5-nitro substituted phthalodinitriles (X = Br 1, I 2) were crystallized from Me2SO solutions affording crystalline adducts (1 -2)center dot Me2SO, which were characterized by X-ray crystallography at various temperatures (>40 K). The two adducts are isomorphic and exhibit in their XRD structures the heteroleptic dipole-dipole four-center contacts between the S=O and G N functionalities. Results of DFT calculations within the molecular approach based on the experimental X-ray geometries of (1-2)center dot Me2SO followed by the topological analysis of the electron density distribution (QTAIM analysis) at the M06-2X/x2c-TZVPPall level of theory confirm the presence of sulfoxide-nitrile heteroleptic dipole-dipole interactions in the solid state (their estimated strength does not exceed 7 kcal/mol). DFT calculations for 1 center dot Me2SO were also performed in both the periodic and molecular models at the DFT M06 level of theory using DZVP and pob-TZVP bases; the results of the electron density topological analysis are similar in both models.