Hg₃Se(SeO₃)(SO₄): A Mixed-Valent Selenium Compound with Mid-Infrared Transmittance Obtained by In Situ Reaction

Exploring new material systems is a highly significant task in the field of inorganic chemistry. A new mixed-valent selenium compound, Hg₃Se(SeO₃)(SO₄), was successfully synthesized through in situ reactions. This compound exhibits a novel three-dimensional structure composed of Hg₃Se(SO₄) layers bridged by SeO₃ trigonal pyramids. It is the first structure containing (SeO₃)^2-, (SO₄)^2-, and Se^2- simultaneously. In addition, Hg₃Se(SeO₃)(SO₄) possesses a wide bandgap (3.5 eV), moderate birefringence (Cal:0.064@546 nm, Exp:0.069@546 nm), a high laser-induced damage threshold (23.35 MW cm^-2), and a wide transmittance window (0.28-6.6 μm). Our work demonstrates that mixed-valent (+4, -2) selenite selenide can be potential optical materials for the mid-infrared region.