A novel symmetric pyrazine (pyz)-bridged uranyl dimer [UO 2 Cl 3 (H 2 O)(Pyz) 0.5 ] 2 2- : synthesis, structure and computational analysis.

Herein we report on the synthesis of (HPyz + ) 2 [UO 2 Cl 3 (H 2 O)(Pyz) 0.5 ] 2 ·2H 2 O which features a novel pyrazine-bridged uranyl dimer, [UO 2 Cl 3 (H 2 O)(Pyz) 0.5 ] 2 2- . A rigorous computational and experimental analysis of this compound was performed to fully explore the influence of coordination on the electronic structure and potential charge-transfer characteristics of this dimer, revealing a delocalized π-system across the bridging pyrazine and the axial components of both uranyl centers. Electrostatic surface potentials, used to rationalize the observed assembly, indicate a decreased basicity of the uranyl oxo versus [UO 2 Cl 4 ] 2- , and signify a lessened capacity for the terminal -yl oxos of the [UO 2 Cl 3 (H 2 O)(Pyz) 0.5 ] 2 2- dimer to participate in supramolecular assembly. A combined density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) analysis further evidenced an increase in UO bond strengths within the dimer, which is supported by a blue shift in the characteristic Raman-active uranyl symmetric stretch ( ν 1 ) with respect to the more typically observed [UO 2 Cl 4 ] 2- .