Gd3Cu2Te7 and U2Cu0.78Te6: Two Examples of Linear Te Chains

The compounds Gd3Cu2Te7 and U2Cu0.78Te6 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) ? 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. U2Cu0.78Te6 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) ?, and =98.978(3)° at T= 153 K. U2Cu0.78Te6 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.