Substituent Effects in the Noncovalent Bonding of SO2to Molecules Containing a Carbonyl Group. The Dominating Role of the Chalcogen Bond.
The SO2molecule is paired with a number of carbonyl-containing molecules, and the properties of the resulting complexes are calculated by high-level ab initio theory. The global minimum of each pair is held together primarily by a S···O chalcogen bond wherein the lone pairs of the carbonyl O transfer charge to the π* antibonding SO orbital, supplemented by smaller contributions from weak CH···O H-bonds. The binding energies vary between 4.2 and 8.6 kcal/mol, competitive with even some of the stronger noncovalent forces such as H-bonds and halogen bonds. The geometrical arrangement places the carbonyl O atom above the plane of the SO2molecule, consistent with the disposition of the molecular electrostatic potentials of the two monomers. This S···O bond differs from the more commonly observed chalcogen bond in both geometry and origin. Substituents exert their influence via inductive effects that change the availability of the carbonyl O lone pairs as well as the intensity of the negative electrostatic potential surrounding this atom.
Instituto de Química Médica, CSIC , Juan de la Cierva, 3, E-28006, Madrid, Spain.|Department of Chemistry and Biochemistry, Utah State University , Logan, Utah 84322-0300, United States.
Luis Miguel
LM
Azofra
Department of Chemistry and Biochemistry, Utah State University , Logan, Utah 84322-0300, United States.
Steve
S
Scheiner