Sodium copper borate, Na2Cu2B12O2121, is a member of the Na2M2B12O (M(II) = Ni, Cu and Co) structure type. It has been synthesized by a solid-state reaction. Single-crystal XRD analysis showed that it crystallizes in the monoclinic system, I 2/a space-group with a = 17.353(1), b = 4.671(1), c = 19.672(1)Å, ß= 101.42(1)°, Z = 4. The new anhydrous borate shows a 3-D framework crystal structure. It contains a discernible tunnel structure constructed from BO4 tetrahedra, BO3 trigonal units and CuO6 octahedra. Seven-coordinate Na+ cations lie in the large tunnels that extend along the b axis. This structural model is validated by the charge distribution (CD) analysis.
Na2Cu2B12O21, Crystal structure, X-ray diffraction, Charge distribution (CD)