A New Lithium Rubidium Borate Li<sub>6</sub>Rb<sub>5</sub>B<sub>11</sub>O<sub>22</sub> with Isolated B<sub>11</sub>O<sub>22</sub> Building Blocks

A new noncentrosymmetric polyborate, Li<sub>6</sub>Rb<sub>5</sub>B<sub>11</sub>O<sub>22</sub>, has been designed and synthesized in the Li<sub>2</sub>O–Rb<sub>2</sub>O–B<sub>2</sub>O<sub>3</sub> ternary system. The structure of the title compound was solved by single crystal X-ray diffraction analysis. It crystallizes in the monoclinic space group <i>C</i>2<i>.</i> The new structure contains an infinite three-dimensional matrix that is built from B<sub>11</sub>O<sub>22</sub> building blocks and LiO<sub><i>n</i></sub> (<i>n</i> = 4, 5), RbO<sub><i>n</i></sub> (<i>n</i> = 9, 10) polyhedra. The B<sub>11</sub>O<sub>22</sub> building block has not been reported previously in any anhydrous and hydrated borates. The optical characterization of the compound indicates that its UV cutoff edge is below 190 nm. IR spectroscopy, thermal analysis, and second-harmonic generation were also performed on the reported material.