New copper(II)–lone electron pair elements–oxyhalides compounds: syntheses, crystal structures, and magnetic properties

We report the results of the investigation of three phase diagrams: (i) CuO–CuCl2–SeO2, (ii) CuO–CuCl2/CuBr2–TeO2 and (iii) CuO–CuCl2/CuBr2–SeO2–Bi2O3. Four compounds have been isolated Cu3(SeO3)2Cl2, Cu9O2(SeO3)4Cl6, Cu2Te2O5X2 (X=Cl, Br) and Cu3Bi(SeO3)2O2X (X=Cl, Br). Interesting structural arrangements are observed for the latter two: tetrahedral clusters of copper(II) ions for Cu2Te2O5X2 and copper(II)–oxygen layers of hexagonal shape made of [CuO4] square planes sharing apices whose geometry is reminiscent of a kagomé type lattice. These compounds provide good experimental realizations of S=1/2 low-dimensional 1D and 2D magnetic materials. The analysis of the magnetic susceptibility of Cu2Te2O5X2 reveals that the bricks are effectively tetrahedra with all couplings roughly equivalent; J1=J2 with J1=38.5 K for the chlorine compound and J1=43 K for the bromine one. For Cu3Bi(SeO3)2O2Cl, a striking behavior is observed like, for instance, an absence of Cu2+ spin resonance at ν=9.44 GHz.