Gd₃Cu₂Te₇ and U₂Cu_0.78Te₆: Two examples of linear Te chains

The compounds Gd₃Cu₂Te₇ and U₂Cu_0.78Te₆ have been synthesized by reactions of the elements at 1123 K in a KI flux. Gd₃Cu₂Te₇ crystallizes in the orthorhombic space group Cmcm with four formula units in a cell of dimensions a=11.4994(8), b=19.170(1), and c=6.1251(4) Å at T=153 K. Gd₃Cu₂Te₇ can be considered to consist of one-dimensional isolated Te chains and two-dimensional _∞²[Cu₂Te₅] layers separated by Gd atoms along the b axis. U₂Cu_0.78Te₆ crystallizes in the monoclinic space group P2₁/m with one formula unit in a cell of dimensions a=6.100(1), b=4.2150(7), c=10.365(2) Å, and β=98.978(3)° at T=153 K. U₂Cu_0.78Te₆ contains two-dimensional _∞²[UTe₃] layers joined by Cu atoms along the c axis. In both structures the Gd and U atoms are coordinated to bicapped trigonal prisms of eight Te atoms, and the Cu atoms are coordinated to tetrahedra of four Te atoms. Both structures contain linear Te chains.