New alkali-metal bidentate borate–malate NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2⋅H2O: Effect of cations on the framework structures and macroscopic centricities

•New borate–malate crystals NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2⋅H2O have been grown.•They display diverse framework geometries attributable to the size of the cations.•NaB(DL-C4H4O5)2 crystallizes in the noncentrosymmetric monoclinic space group P2.•Both crystals have absorption edges about 220 nm in the UV region.•NaB(DL-C4H4O5)2 exhibits a NLO efficiency of 2 times that of KDP (KH2PO4) standard.

Two new alkali-metal bidenate borate–malate NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2⋅H2O have been grown by the facile slow evaporation method through the introduction of acetone as solvent. The crystal structures were determined by single crystal X-ray diffraction. The stoichiometrically equivalent materials crystallize in three-dimensional framework structures and have the same structural unit [B(C4H4O5)2]−. However, both crystals exhibit very diverse framework geometries attributable to the size of the alkali-metal cations, which also leads to the different space groups and macroscopic centricities as proven by SHG test. The noncentrosymmetric NaB(DL-C4H4O5)2 was found to exhibit phase-matchable NLO intensity as high as two times that of KDP standard and a short-wavelength absorption onset at 220 nm. Moreover, both crystals have also been characterized by Infrared spectroscopy and thermogravimetric analysis.

Graphical abstractTwo novel semiorganic borates NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2H2O display different framework geometries attributable to the size of the alkali-metal cations. NaB(DL-C4H4O5)2 exhibits SHG intensity as high as two times that of KDP.Figure optionsDownload full-size imageDownload as PowerPoint slide