Synthesis, crystal structures, and magnetic properties of one-dimensional alkali metal copper chlor-tellurites A(NH4)Cu4Te2O6Cl6 (A = K, Cs), NaCu4Te2Cl5O6 and Rb3(NH4)2Cu12Te6Cl16.5O18(OH)0.5.

Abstract

Four new alkali metal copper chlor-tellurites, [Cs(NH4)]layer[Cu4Te2O6Cl6]layer (I), [Rb3(NH4)2(OH)0.5]layer[Cu12Te6Cl16.5O18]layer (II), [K(NH4)]layer[Cu4Te2O6Cl6]layer (III) and [NaCl]layer[Cu4Te2O6Cl4]layer (IV), have been synthesized via hydrothermal reactions using mixtures of AF (A = Cs, Rb, K, Na), CuCl2·2H2O, TeO2, and hydrazine monohydrate. They have two-dimensional (2D)-layered [Cu4Te2Cl5+x-yO6]∞ (x = 0, 2/3, 1; y = 0, 1/6) structures that are separated by different layers comprised of various cations and anions, including A+, NH4+ Cl- OH-, etc. The blocks feature S-shaped ∞[Cu2O3Cl3-x] chains linked by TeO3 trigonal pyramids. The magnetic susceptibility shows a broad maximum at 220 K for I and 240 K for III, which is well simulated by using an alternating antiferromagnetic chain model. The J2/J1 ratio within the alternating chain is estimated to be 0.60(1), and the spin gaps are refined to be 152 K for I and 136 K for III.