Synthesis and crystal structure of a new strontium borate, Sr2B16O26

A new strontium borate, Sr2B16O26, has been prepared by solid-state reactions at temperature below 750 degrees C. The single-crystal X-ray structural analysis showed that Sr2B16O26 crystallizes in the monoclinic space group P2(l)/c with a= 8.408(1) angstrom, b= 16.672(2) angstrom, c= 13.901(2) angstrom, beta = 106.33(1)degrees, and Z = 4. Its crystal structure consists of a 3D network of the complex borate anion [B16O20O12/2](4-), formed by 12 BO3 triangles and 4 BO4 tetrahedra, which can be viewed as 3 linked [B3O3O4/2](-) triborate groups bonded to 1 pentaborate [B5O6O4/2](-) group and 2 BO3 triangles; this leads to a Fundamental Building Block (FBB) with the shorthand notation 16: infinity (3)[3 x (3:2 Delta + T) + (5:4 Delta + T) + 2 Delta]. The 3D network affords intersecting open channels running parallel to the crystallographic a and c axes, where Sr2+ cations reside. The IR spectrum further confirms the presence of both BO3 and BO4 groups. (C) 2007 Elsevier Masson SAS. All rights reserved.