PNNL

Abstract

The strong intramolecular Coulomb repulsion in multiply charged anions (MCAs) creates a potential barrier that provides dynamic stability to MCAs and allows electronically metastable species to be observed. The 1-hydroxy-3,6,8-pyrene-trisulfonate {[Py(OH)(SO3)3]3- or HPTS3-} was recently observed as a long-lived metastable MCA with a large negative electron binding energy of -0.66 eV. Here we use Penning trap mass spectrometry to monitor the spontaneous decay of HPTS3- f HPTS•2- + e- and have determined the half-life of HPTS3- to be 0.1 s. To explore the limit of electronic metastability, we tried to make the related quadruply charged pyrene-1,3,6,8-tetrasulfonate {[Py(SO3)4]4-}. However, only its decay product, the triply charged radical anion [Py(SO3)4]•3-, as well as the triply charged ion-pairs [Py(SO3)4H]3- and [Py(SO3)4Na]3-, was observed, suggesting that the tremendous intramolecular Coulomb repulsion makes the [Py(SO3)4]4- anion extremely short-lived. Photoelectron spectroscopy data showed that [Py(SO3)4]•3- is an electronically stable species with electron binding energies of +0.5 eV, whereas [Py(SO3)4H]3- and [Py(SO3)4Na]3- possess electron binding energies of 0.0 and -0.1 eV, respectively. Ab initio calculations confirmed the stability of these triply charged species and further predicted a large negative electron binding energy (-2.78 eV) for [Py(SO3)4]4-, consistent with its short lifetime