Our recent reevaluation of molecular oxide Tc2O7, including a new single crystal structure study and electron-impact mass spectroscopy (EI-MS). Differences in the EI-MS indicates Tc2O7 should behave differently compared to Re2O7 in the gas phase. Motivated by this, we investigated the molecular and electronic structures of both the isolated molecules and solid-state structures of the group 7 heptoxides using density functional theory. Bonding analysis of the isolated molecules of each species show the presence of unusual three-center covalent bond between the metal atoms and the bridging oxygen. Differences in the covalent character of this bond explains the observed differences in gas phase molecular structures. The solid-state simulations correctly predict the known crystal structures within a few percent. Analysis of the bonding bands in the solid-state also show the presence of the three-center covalent bond. Homologue studies of Tc2O7 show why a linear molecular configuration is preferred in the solid-state. Homologue and compression studies of Re2O7 show why a polymeric structure is adopted instead of a molecular one like Mn and Tc.

Molecular and electronic structures of the group 7 heptoxides

254th National Meeting (2017)

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