New germanate and mixed cobalt germanate salt inclusion materials: [(Rb6F)(Rb4F)][Ge14O32] and [(Rb6F)(Rb3.1Co0.9F0.96)][Co3.8Ge10.2O30F2]

Abstract

Single crystals of two new germanates, [(Rb₆F)(Rb₄F)][Ge₁₄O₃₂] and [(Rb₆F)(Rb_3.1Co_0.9F_0.96)][Co_3.8Ge_10.2O₃₀F₂], were synthesized via high temperature RbCl/RbF flux growth. Both compounds crystallize in the cubic space group F3m and possess the germanium framework of the previously reported salt inclusion material (SIM), [(Cs₆F)(Cs₃AgF)][Ge₁₄O₃₂], related to the Ge₇O₁₆ zeolitic family. These materials demonstrate the ability to accommodate a variety of salt-inclusions, and exhibit chemical flexibility enabling modifications of the framework through incorporation of Co. Alteration of the salt-inclusion led to intrinsic luminescence of [(Rb₆F)(Rb₄F)][Ge₁₄O₃₂] while modification of the framework resulted in an unanticipated Rb/Co salt/inclusion in [(Rb₆F)(Rb_3.1Co_0.9F_0.96)][Co_3.8Ge_10.2O₃₀F₂]. Fluorescence measurements were performed on [(Rb₆F)(Rb₄F)][Ge₁₄O₃₂]. First-principles calculations in the form of density functional theory (DFT) were performed for [(Rb₆F)(Rb_3.1Co_0.9F_0.96)][Co_3.8Ge_10.2O₃₀F₂] to elucidate its electronic and magnetic properties, and stability at 0 K.