Syntheses, structures, and magnetic properties of the europium(II) selenido pnictogenates(III), EuPnSe3 (Pn=Sb, Bi)

EuPnSe3 (Pn=Sb, Bi) have been synthesized through the reaction of Eu with Pn2Se3 (Pn=Sb, Bi) and Se at 850–900 °C. These compounds are isotypic with SrPnSe3 (Pn=Sb, Bi) and consist of square pyramidal PnSe5 units and distorted PnSe6 octahedra that form hollow columns that extend along the c-axis. These columns are separated by Eu2+ cations that occur as nine-coordinate tricapped trigonal prisms. There are also additional V-shaped triselenide Se32− anions between the columns that bind the Eu2+ cations. The Se⋯Se contacts (in EuSbSe3) in these units are 2.4584(11) and 2.4359(11) Å, which are consistent with Se–Se single bonds. The overall structure is chiral. Bond-valence sum calculations indicate that these compounds contain Eu2+. Magnetic susceptibility measurements provide values of 7.66 μB/Eu for EuSbSe3 and 7.64 μB/Eu for EuBiSe3, which are close to the expected free-ion moment for Eu2+. These compounds follow essentially Curie behavior from 300 to 5 K, and undergo an apparently antiferromagnetic transition below 5 K. Crystallographic data: EuSbSe3, orthorhombic, space group P212121, image, image, image, image, image, image for 183 parameters and 5095 reflections with image; EuBiSe3, orthorhombic, space group P212121, image, image, image, image, image, image for 183 parameters and 4895 reflections with image.