Quantum-chemical study of stability, aromaticity and reactivity properties on O- and S-heterocyclic divalent five-memberedRings C2H2X2M (X=O and S; M=C, Si, Ge, Sn and Pb)

In the present work, Density functional theory computations have been carried out at B3LYP LANL2DZ level of theory to obtain the singlet-triplet energy, stability, aromaticity and reactivity properties of O- and S-heterocyclic five-membered divalent carbenes C2H2X2M (X = O and S; M = C, Si, Ge, Sn and Pb). The stabilization energies (SEs) are calculated using five isodesmic reactions. All calculations were carried out in the gas phase at room temperature and 1 atm pressure. The results indicate that the singlet states of molecules are more stable than their triplet states. All molecules have a planar conformer. The stability of C2H2X2M decreases from M = C to M = Pb. In contrast, the reactivity of heterocyclic carbenes is increases from M = C to M = Pb. The nucleus-independent chemical shift calculations have not effect in the stabilizing of molecules.