Exploratory investigation of new SHG materials based on galloborates

Three new galloborates, namely, GaB(5)O(8)(OH)(2)(en)(2)·H(2)O (1), LiGa(OH)(BO(3))(H(2)O) (2), and Rb(2)Ga(B(5)O(10))(H(2)O)(4) (3), have been synthesized by hydrothermal reactions. Compound 1 is the first example of a galloborate that contains an organic component. It crystallizes in space group P2(1)/c, and its crystal structure exhibits an infinite zigzag chain consisting of [B(5)O(8)(OH)(2)](3-) anions and GaO(2)N(4) octahedra interconnected via corner sharing. Compound 2 crystallizes in space group P31c with a layered structure composed of GaO(4), LiO(4), and BO(3) building units. Compound 3 belongs to chiral space group C222(1); the basic building blocks of the structure are the [B(5)O(10)](5-) cluster anion and GaO(4) tetrahedron, which are interconnected to form a three-dimensional network with tunnels of Ga2B6 eight-membered rings (8-MRs) which are filled by Rb(+) cations and lattice water molecules. Interestingly, Rb(2)Ga(B(5)O(10))(H(2)O)(4) displays a moderate second-harmonic generation (SHG) response comparable to that of KH(2)PO(4) (KDP), and it is phase matchable. Band structure and optical property calculations for Rb(2)Ga(B(5)O(10))(H(2)O)(4) based on DFT methods were also performed.