Synthesis, Crystal Structure, and Nonlinear Optical Properties of Li<sub>6</sub>CuB<sub>4</sub>O<sub>10</sub>:  a Congruently Melting Compound with Isolated [CuB<sub>4</sub>O<sub>10</sub>]<sup>6-</sup> Units

Single crystals of Li<sub>6</sub>CuB<sub>4</sub>O<sub>10</sub> have been synthesized, and its crystal structure has been determined. Li<sub>6</sub>CuB<sub>4</sub>O<sub>10</sub> crystallizes in the non-centrosymmetric triclinic space group <i>P</i>1 (No. 1). The structure consists of isolated [CuB<sub>4</sub>O<sub>10</sub>]<sup>6-</sup> polyanions that are bridged by six LiO<sub>4</sub> tetrahedra. Li<sub>6</sub>CuB<sub>4</sub>O<sub>10</sub> is a congruently melting compound. It produces SHG intensity similar to that produced by KH<sub>2</sub>PO<sub>4</sub> and is phase-matchable.