Synthesis, crystal structure and magnetic properties of Li2InMO3O8: A novel reduced molybdenum oxide containing magnetic Mo3 clusters

Powder samples and single crystals of Li2InMo3O8 were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction (771 independent reflections for 33 refinable, R1=0.0158 and wR2=0.0354). Li2InMo3O8 is isomorphous with Li2SnMo3O8 and crystallizes in the hexagonal space group P6(3)mc with unit-cell parameters a=5.7931(2) angstrom, c=10.4681(4) angstrom and Z=2. The crystal structure consists of distorted hexagonal-close-packed oxygen layers with stacking sequence abac along [0 0 1] and that are held together by alternating lithium-indium and molybdenum layers. The Li+ and In3+ ions occupy, respectively, tetrahedral and octahedral sites in the ratio 2:1. The Mo atoms occupy octahedral sites and form strongly bonded triangular clusters involving three MoO6 octahedra that are each shared along two edges, constituting a Mo3O13 unit. The variations of the Mo-Mo and Mo-O bond lengths according to the number of electrons per Mo-3 cluster are discussed. The trivalent oxidation state of the indium leads to one unpaired electron per Mo-3 and thus gives rise to a paramagnetic spin behavior with an effective magnetic moment of 1.5 mu(B) per Mo-3 cluster. The magnetic susceptibility vs. temperature curve also shows a maximum at 25 K arising probably from an antiferromagnetic ordering between the Mo-3 clusters. (C) 2013 Elsevier Inc. All rights reserved.