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[Cu₁₂Te₆Cl_16.5O₁₈]_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 [Cu₄Te₂Cl_5+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 _∞[Cu₂O₃Cl_3−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.