Flux Synthesis, UV–vis Absorbance, and Magnetism of Cesium Copper Silicates with an Isolated Super-Super Exchange Spin Dimer in Cs6Cu2Si9O23

Single crystals of four new cesium copper silicates were grown from CsCl/CsF flux. [CsCs₄Cl][Cu₂Si₈O₂₀] is a salt-inclusion compound that crystallizes in space group P4/m with lattice parameters a = 12.2768(3) Å and c = 8.6470(2) Å; Cs₆Cu₂Si₉O₂₃ crystallizes in space group P2₁/n with lattice parameters a = 15.0763(9) Å, b = 6.9654(4) Å, c = 26.9511(17) Å, and β = 99.240(2)°; Cs₈Cu₃Si₁₄O₃₅ crystallizes in space group C2/c with a = 39.2236(13) Å, …