A Chiral Lead Borate Containing Infinite and Finite Chains Built up from BO₄ and BO₃ Units

With a hydrothermal technique, a novel chiral lead borate (Pb 6 B 11 O 18 (OH) 9 ) has been prepared. The sample has been characterized by powder X-ray diffraction, infrared spectroscopy, energy-dispersive spectroscopy, thermal analysis, and second-harmonic generation powder measurement. The structure of the compound, which crystallizes in the trigonal space group P 3 2 with lattice constants a = 11.7691(7) Å and c = 13.3361(12) Å has been solved by single-crystal X-ray diffraction analysis. There exist infinite helical chains and finite chain fragments built up from BO 4 and BO 3 units. In the compound the Pb 2+ cations are located in the space between adjacent polyborate anionic chains, compensating the negative charges of the chains. The chiral feature of the lead borate is unique, and because it lacks symmetry center, the compound exhibits distinct NLO properties.