Sulfur Cluster Dianions

Free dianionic sulfur clusters have been studied by standard ab initio methods. Chainlike S n 2- isomers have been found to exhibit nonlinear twisted geometries, and the onset of electronic stability in this series is predicted to occur at n = 7. S 8 2- is the smallest system clearly stable with respect to electron autodetachment and is predicted to be sufficiently long-lived to allow the observation in a mass spectrometer. Branched isomers have been found to be electronically more stable than the corresponding chainlike isomers but are expected to be more sensitive to fragmentation. The bonding mechanisms of the excess electrons in the different isomers are discussed, and the stable systems are compared to other small gas-phase dianions. Our results broaden the overall picture of isolated dianionic species.