A novel orthoborate, NaMgBO(3), has been successfully synthesized by a standard solid-state reaction, and the crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the monoclinic space group C2/c with lattice parameters a = 5.01313(6) Angstrom, b = 8.8007(1) Angstrom, c = 5.52831(7) Angstrom, and beta = 99.6962(6) degrees. Isolated [BO(3)](3-) anionic groups, which are the fundamental building units, are distributed perfectly parallel to each other. It is a typical structure of big birefringent crystals. The overall structure is similar to that of NaSrBO(3), which crystallizes in P2(1)/c. The correlation between these two structures is discussed. The Mg atoms in NaMgBO(3) are used instead of the position of Na in NaSrBO(3), while the Na atoms occupy the position of Sr. Then the directions of the BO(3) triangles are changed to balance the bond valence, which leads to a higher symmetry. They are the first pair of alkali-alkaline earth orthoborates with close space groups by exchange of the cation positions.

A novel chiral orthoborate, KMgBO(3), has been successfully synthesized via a standard solid-state reaction, and the crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the cubic chiral space group P2(1)3. Isolated [BO(3)](3-) anionic groups, which are the fundamental building units, are distributed around the 111 crystallographic direction in an axial C(3) symmetry, and the configuration of O(3) planes is helical, similar to the aplanar ClO(3) groups in NaClO(3), which indicates an optical activity in it and is validated by the circular dichroism spectrum. The chiral feature of the borate is unique, and because of the noncentrosymmetric structure, the compound exhibits nonlinear optical properties, which are validated by second harmonic generation powder measurement. It has a wide transparency, including the vacuum ultraviolet region. The relations between the structures of KMgBO(3) and NaClO(3) and structural conversion form KMgBO(3) to NaMgBO(3) are also discussed. The ionic radii, interatomic distance, and the rigid tilting of BO(3) groups are considered to be the main factors in the crystallization of different structures.