Triangular Zn₃and Ga₃units in Sr₂Au₆Zn₃, Eu₂Au₆Zn₃, Sr₂Au₆Ga₃, and Eu₂Au₆Ga₃– structure, magnetism,¹⁵¹Eu Mössbauer and^69;71Ga solid state NMR spectroscopy

Abstract

The gold-rich intermetallic compounds Sr2Au6Zn3, Eu2Au6Zn3, Sr2Au6Ga3, and Eu2Au6Ga3 were synthesized from the elements in sealed tantalum ampoules in induction or muffle furnaces. The europium compounds are reported for the first time and their structures were refined from single crystal X-ray diffractometer data: Sr2Au6Zn3 type, R3̅c, a = 837.7(1), c = 2184.5(4) pm, wR2 = 0.0293, 572 F2 values for Eu2Au6.04Zn2.96 and a = 838.1(2), c = 2191.7(5) pm, wR2 = 0.0443, 513 F2 values for Eu2Au6.07Ga2.93 with 20 variables per refinement. The structures consist of a three-dimensional gold network with a 6R stacking sequence, similar to the respective diamond polytype. The cavities of the network are filled in a ratio of 2:1 by strontium (europium) atoms and Ga3 (Zn3) triangles in an ordered manner. Sr2Au6Zn3 and Sr2Au6Ga3 are diamagnetic with room temperature susceptibilities of –3.5 × 10−4 emu mol–1. Temperature dependent susceptibility and 151Eu Mössbauer spectroscopic measurements show a stable divalent ground state for both europium compounds. Eu2Au6Zn3 and Eu2Au6Ga3 order antiferromagnetically below Néel temperatures of 16.3 and 12.1 K, respectively. Anisotropic electrical conductivity of Sr2Au6Ga3 is proven by an alignment of the crystallites in the magnetic field. Orientation-dependent 69;71Ga NMR experiments combined with quantum mechanical calculations (QM) give evidence for a highly anisotropic charge distribution of the Ga atoms.

Ca2Ga4Ge6 and Ca3Ga4Ge6: Synthesis, Structure, and Electronic Properties

“…Previous reports of similar three membered rings include Sr 2 Au 6 Ga 3 and Eu 2 Au 6 Ga 3 , both of which contain Ga 3 triangular units. [17] While the triangular moiety is rare, the overall GaÀ Ge interactions are strong and have an average bond distance of 2.51(4) Å which agrees with the 2.51 Å GaÀ Ga bond distance reported by Kanatzidis et. al in Yb 2 Ga 4 Ge 6 .…”

“…The analogous Yb 2 Ga 4 Ge 6 structure shares this same unique, three‐membered, triangular Ge 2 Ga rings, which are occasionally observed in other compounds featuring group 13 atoms. Previous reports of similar three membered rings include Sr 2 Au 6 Ga 3 and Eu 2 Au 6 Ga 3 , both of which contain Ga 3 triangular units [17] …”

Unveiling the quantum secrets of triel metal triangles: a tale of stability, aromaticity, and relativistic effects

“…Ga 3 , In 3 , and Tl 3 trimers have also been previoulsy studied. Pöttgen and coworkers have characterized many crystal structures where Al 3 , 17 Ga 3 , 18–21 and In 3 , 22–24 triangles are present, and there are many other similar structures reported in the literature. 25–27 Some molecules where Ga 3 triangles are identified have also been synthesized.…”

Revealing Tendencies in the Electronic Structures of Polar Intermetallic Compounds

“…The second group of the active-metal-poor ternary intermetallic compounds, which are composed of an active-metal, gold and a post-transition-element and were taken into consideration for the survey of the previously reported −ICOHP/bond values and their respective percentages to the net bonding capabilities, contains those materials whose crystal structures comprise hexagonal-diamond-fashioned gold networks. In particular, the voids in the hexagonal-diamond-fashioned gold networks, which have to date been observed for four different types of structure and diverse combinations of gold with active metals (Sr, Ba, or Eu) and post-transition-metals (Zn, Cd, Al, Ga, In, or Sn) [132][133][134][135][136][137][138], enclose the active-metal atoms or triangles composed of the gold and the post-transition-metal atoms. Because the crystal structures of some of the inspected active-metal-poor intermetallic compounds comprise atomic sites with positional and/or occupational disorders (Table 4), the electronic structures of these materials were examined for models which approximate the actual crystal structures and often correspond to the lowest total energies.…”