Theoretical investigation of the relative stabilities of singlet and triplet disulfides

Abstract

Ab initio molecular orbital calculations have been performed on the singlet ( 1A) and triplet ( 3A u) states of hydrogen persulfide (HSSH) at the SCF and post-SCF levels using a double zeta basis set augmented with polarization functions. The relative energies for this system were computed by many-body perturbation theory (MBPT) and coupled-cluster (CC) methods, indicating that the singlet and triplet states are both lower in energy than the isolated HS fragments. Structural information for 1[HSSH] determined at the SCF and post-SCF levels are in good agreement with experiment. The triplet state is very weakly bound (<5 kcal/mol) and lies approximately 50 kcal/mol above the singlet state.