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

Single crystals of four new cesium copper silicates were grown from CsCl/CsF flux. [CsCsCl][CuSiO] is a salt-inclusion compound that crystallizes in space group 4/ with lattice parameters = 12.2768(3) Å and = 8.6470(2) Å; CsCuSiO crystallizes in space group 2/ with lattice parameters = 15.0763(9) Å, = 6.9654(4) Å, = 26.9511(17) Å, and β = 99.240(2)°; CsCuSiO crystallizes in space group 2/ with = 39.2236(13) Å, = 6.9658(2) Å, = 14.9115(5) Å, and β = 97.1950(10)°; and CsCuSiO is a member of the stuffed tridymite family and crystallizes in a monoclinic distortion of the CsAlSiO structure type with space group 2/ and = 12.8587(3) Å, = 5.38510(10) Å, = 9.0440(2) Å, and β = 133.2580(10)°. All four compounds contain CuO-flattened tetrahedra. The degree of flattening can be correlated with the UV-vis spectra. CsCuSiO exhibits spin dimer magnetism that can be attributed to super-super-exchange between two Cu(II) ions connected by a silicate tetrahedron. The other three compounds all show paramagnetic behavior down to 2 K.