Two Acentric Aluminoborates Incorporated d 10 Cations: Syntheses, Structures, and Nonlinear Optical Properties.

Two acentric aluminoborates (ABOs), [Zn(en) 2 Al{B 5 O 9 (OH)}{BO(OH) 2 }] ( 1 ) and [Cd(en) 2 AlB 5 O 10 ]·H 2 O ( 2 ) (en = ethylenediamine), have been solvothermally made. 1 includes a two-dimensional (2D) wavy ABO layer using B 5 O 9 (OH) clusters and AlO 3 {BO(OH) 2 } groups, in which both units can be regarded as three-connected nodes, and simplifying the ABO layer to a hcb -type network. 2 features an acentric three-dimensional (3D) porous framework with a unique unc -type network constituted by strictly alternating connected B 5 O 10 clusters and AlO 4 units. The structural transformation from a 2D layer 1 to a 3D framework 2 was achieved with the elimination of the terminal hydroxyls in layer 1 by adjusting synthetic conditions in the same solvent system. Metal-amine complexes Zn(en) 2 /Cd(en) 2 bond to the inorganic walls and are located in the cavity of frameworks 1 and 2 , respectively. Compounds 1 and 2 exhibit large second-harmonic generation (SHG) responses that are 2.2 and 2.7 times those of KH 2 PO 4 (KDP), respectively, which are among the largest powder SHG responses for all deep-ultraviolet (deep-UV) ABOs. The UV-vis diffuse reflectance spectra of 1 and 2 show a wide transparency window below 190 nm. Density functional theory (DFT) calculations indicate that the B-O units and the introduced distorted d 10 metal polyhedra played a decisive role in the optical properties of both compounds.