Atomic Charge Distribution and Chemical Bonding in Isolated Molecules of 3,4-Dihydro-1H-Benzo[c][1,2]Thiazine 2,2-Dioxide Derivatives

The atomic charge (re)distribution in isolated molecules of 3,4-dihydro-1H-benzo[c][1,2]thiazine 2,2-dioxide derivatives, arising from covalent bonding and nonclassical hydrogen bonding of the [C(sp3)–] H⋯N type, is analyzed in terms of the superposition of the conservative vector fields of the electrostatic force Fes(r), the total static force Fem(r), and the electron density gradient ∇ρ(r). For the molecules studied, the distribution of the exchange charge density qx(r) = ∇·Fx(r)/(4π), evaluated within the local density approximation, enables the characterization of the electron pair on the pyramidal nitrogen atom in the sulfonamide group and clarifies its role in the intramolecular H⋯N interatomic interaction.