Li2CsB7O10(OH)4: A Deep-Ultraviolet Nonlinear-Optical Mixed-Alkaline Borate Constructed by Unusual Heptaborate Anions.

A new noncentrosymmetric mixed-alkaline borate, Li2CsB7O10(OH)4 (1), was made under solvothermal conditions. This layered boron oxide framework consists of unique bird-shaped [B7O12(OH)4]7- clusters with large 14-ring pores. Its second-harmonic-generation (SHG) signal is 2.5KDP (KH2PO4), with its short ultraviolet (UV) cutoff edge indicating that this crystal is a potential deep-UV transparent nonlinear-optical material.