Synthesis and crystal structure of Eu2ReO5, a complex oxide with Re-Re pairs in a tetragonal antiprismatic coordination

The europium rhenium oxide Eu2ReO5 has been synthesized by solid state reaction of Eu3ReO8 with metallic rhenium and europium oxide Eu2O3 at 1450 K in sealed silica ampoules. The crystal structure was determined by X-ray diffraction analysis on a twinned specimen. It crystallizes in the tetragonal space group P4/n (No. 85, a=865.3(1) pm, c=573.9(1) pm; Z=4). The main feature of the crystal structure is the formation of Re-Re pairs surrounded by eight oxygen atoms in a tetragonal antiprismatic configuration. The Re2O8 units are stacked building columns 1∞[Re2O8-Re2O8] running along [001]. The compound is a semiconductor with an optical band gap of 1.4 eV. (orig.)