Na₂B₁₂Si₆Se₁₈: A Novel B₁₂-Cluster-Containing Quaternary Selenoborate Framework Material

We report the successful synthesis of the new quaternary, three-dimensional Na2Si6B12Se18 material using a solid-state synthesis route. This compound is characterized by a unique framework structure that features the rare icosahedral [B12]10+ cation which is connected via Si2Se6 polyhedral units into a 3D framework structure with Na+ ions located inside the channels. The Na2Si6B12Se18 compound crystallizes in the cubic crystal system in the space group Im3¯, with lattice parameter a = 11.91110(10) Å and unit cell volume of 1689.88(4) Å3. The 3D framework of the [Si6B12Se18]2− anion contains B12 icosahedra with six of their edges bridged by tetrahedral SiSe4 groups. The B12 icosahedral units are connected by the SiSe4 tetrahedral units which bridge between each B12 icosahedron. Ultraviolet–Visible (UV-vis) spectroscopy revealed that Na2Si6B12Se18 exhibits semiconducting behavior with an estimated bandgap of 2.1(1) eV. In situ powder X-ray diffraction (PXRD) studies were conducted to investigate the phase formation of this compound as a function of temperature to obtain information of its thermal stability and structural evolution.