Abstract: Under hydrothermal conditions,A hydrated ammonium hydroxy-borate was synthesized based on "Scale Chemistry". Isolated borate anions self-assemble via polymerization to form one dimensional infinite chain, which are linked by hydrogen bonds to form borate sheets. Ammonium ions and water molecules between these sheets connect adjacent sheets via hydrogen bonds. The compound has been characterized by infrared spectroscopy, elemental analysis, and thermogravimetric analysis as well as single crystal X-ray diffraction studies. The results of single crytal X-ray diffraction analysis are in agreement with the results of hypothesis. The compound exhibits an one-dimensional infinite chain that is formed via polymerization of pentaborate anions, with the guest ammonium ions and water molecules residing in the framework. The compound crystallizes in the triclinic system with space group P-1,a=0.76413(15) nm, b=0.92529(19) nm,c=1.1949(2) nm,α=99.49(3)°,β=105.87(3)°and γ=91.57(3)°

Key words: hydrothermal synthesis;crystal structure;borate;self-assemble