Hydrazine-Assisted Synthesis, Structures, Photoelectricity, and Photocatalysis of Ternary Mercury–Tellurostannate Hybrids with Transition-Metal Complexes

Tellurostannates are traditionally prepared by multistep reactions using the tellurides SnTe, SnTe₂, K₄SnTe₄, or A₆SnTe₆ (A = K, Rb, or Cs) as precursors, which are usually prepared by the molten reaction of alkali metals Sn and Te under harsh synthetic conditions. Differently, ternary Hg-tellurostannate hybrids [Mn(en)₃]HgSnTe₃(Te₂) (1) (en = ethylenediamine), [Mn(dien)₂]HgSnTe₃(Te₂) (2), and [Fe(dien)₂]HgSnTe₃(Te₂) (3) (dien = diethylenetriamine) were synthesized by one-pot reactions using Sn and Te powders as starting materials in the presence of hydrazine under mild solvothermal conditions. In 1, HgTe₃ and SnTe₄ units are joined via Te-sharing to form a 1-D polymeric chain [HgSnTe₃(Te₂)]_n^2n-, while the [HgSnTe₃(Te₂)]_n^2n- chains in 2 and 3 are composed of HgTe₄ and SnTe₄ units. The common feature of the [HgSnTe₃(Te₂)^2-]_n chains in 1-3 is that they are constructed by both the telluride anion Te^2- and the polytelluride anion Te₂^2-. 1-3 exhibited strong photocurrent responses with current densities of 5.26, 3.38, and 3.94 μA cm^-2, respectively. They showed effective photocatalytic activities for methylene blue degradation with degradation ratios in the range of 85.3-94.6% after light irradiation for 80 min. Investigation of the photocatalytic mechanism showed that ^•O₂^- radicals and h⁺ holes were the main active substances in the photodegradation.