Electrostatic properties of sydnone derivatives

Abstract

The bonding type and characteristic chemical reactions of the sydnone ring have been investigated by determination of the electron density distribution and electrostatic potential by both experimental and theoretical methods. Thirteen sydnone derivatives with known crystal structures were studied by theoretical AM1, MNDO, and ab initio calculations. Most of these compounds are 3-phenyl- or 3-pyridylsydnone derivatives. The net atomic charges, bond orders, and deformation density distribution maps are presented in comparison with the experimental results from X-ray diffraction. The net atomic charges, bond lengths, and bond orders of these compounds confirm the semiaromatic bonding type for the sydnone ring which was previously assigned by consideration of the experimental bond distances