Synthesis, Crystal Structure, and Electrical Properties of a New Molybdylarsenate LiNa5K3Mo11As3O45

LiNa5K3Mo11As3O45 is a new inorganic compound. It was synthesized by a solid state method. The crystal structure has been studied by single crystal X-ray analysis. The R-values reached 2.8%. The title compound crystallizes in the triclinic system, space group P-1, with a = 10.550 (2) ？, b = 11.723 (2) ？, c = 17.469 (3) ？, α = 102.35 (3)°, β = 87.61 (2)°, and γ = 111.03 (3)°. The anionic unit [Mo11As3O45]9？ is formed by nine MoO6 octahedra, two MoO5 trigonal bipyramids, and three AsO4 tetrahedra. The association of [Mo11As3O45]9？ units, running along [010], leads to a one-dimensional framework. Li, K, and Na are located in the space surrounding the anionic ribbons. This material was characterized by SEM microscopy, IR spectroscopy, and powder X-ray diffraction. The electrical conductivity was investigated from 528？K to 673？K by impedance complex followed by DSC spectroscopy. 1. Introduction The search for new materials, based in arsenic and molybdenum, with an open framework formed by octahedra and tetrahedra showing multiple modes of connections and containing alkali gives a big interest in solid state chemistry [1]. This kind of material shows important energetic property which is the ionic conductivity. We are interested in this field and we have explored the A2O-MoO3-As2O5 systems (A = alkali or silver) in which many compounds were characterized: K2MoO2(MoO2As2O7)2 [2], Na2(MoO2)3(As2O7)2 [3], and NaAg2Mo3O9AsO4 [4]. We have succeeded in the synthesis of a new material LiNa5K3Mo11As3O45. It was prepared by a solid state method. 2. Experimental Details 2.1. Synthesis The LiNa5K3Mo11As3O45 compound was obtained from a mixture of (NH4)2Mo4O13 (Fluka 69858), NH4H2AsO4 (ASTM 01-775), Na2CO3 (Prolabo 27778), K2CO3 (Pan 121490) and LiOH·H2O (Fluka 62530). The mixture was grinded and preheated in air at 673？K to remove NH3, H2O, and CO2. Then, it was grinded and heated again to 808？K. The mixture was left at this temperature for 2 weeks to promote germination and growth of crystals. The final residue was subjected at a first slow cooling (5？K/24？h) in an interval of 50？K and then at a second faster cooling (50？K/h) to reach room temperature. The yellowish crystals obtained by spontaneous crystallization were separated by flow of hot water to do the preliminary identification. 2.2. Single Crystal X-Ray Data Collection It was performed with a CAD-4 Enraf-Nonius X-ray diffractometer [5] at 298？K with graphite monochromator using wavelength. All calculations were performed using the Wingx-98 crystallographic software package [6]. An empirical correction of