A series of novel mercury(i) selenites and tellurites containing SOJT Mo6+ cations

Abstract

Using Hg₂Cl₂, MoO₃, and TeO₂ (or SeO₂) as starting materials, four new mixed-metal tellurites and selenites have been obtained in the unexplored mercury(I)–Mo⁶⁺–Se⁴⁺/Te⁴⁺–O system, namely, Hg₂MoSeO₆ (1), α-Hg₂MoTeO₆ (2), β-Hg₂MoTeO₆ (3), and Hg₂Mo₂TeO₉ (4). They represent the first mercury(I) tellurites and selenites containing octahedrally coordinated d⁰ transition metal (TM) cations. All four compounds are centrosymmetric. They show three types of 3D structures based on Hg₂²⁺ dumbbells, MoO₆ octahedra, QO₃²⁻ (Q = Se, Te) or TeO₄⁴⁻ anions. Compounds 1–3 feature similar 1D anionic chains of [MoO₃(QO₃)]²⁻ (Q = Se or Te), in which the 1D chains of corner-sharing MoO₆ octahedra are further decorated by bidentate bridging selenite or tellurite anions. Compounds 1 and 2 are isostructural and their 3D network structures are based on 2D mercury tellurite or selenite layers in the ac plane pillared by MoO₆ octahedra, whereas the 3D network of β-Hg₂MoTeO₆ (3) is composed of 1D mercury tellurite chains along the a axis and 1D chains of [MoO₃(TeO₃)]²⁻ anions along the b axis. Compound 4 features an unusual 3D network structure composed of novel [Mo₂O₅(TeO₄)]²⁻ double layers interconnected by Hg₂²⁺ cations. Within the [Mo₂O₅(TeO₄)]²⁻ double layer, the cyclo-Mo₄O₂₀ tetramers are further interconnected via corner sharing into a 2D molybdenum oxide double layer with TeO₄ groups capping the walls of the thus-formed eight-membered rings (8-MRs). Thermal stabilities and optical properties as well as theoretical calculations based on density functional theory (DFT) methods were also performed.