Crystal structure and magnetic properties of Co2TeO3Cl2 and Co2TeO3Br2

The crystal structures of the two new synthetic compounds Co2TeO3Cl2 and Co2TeO3Br2 are described together with their magnetic properties. Co2TeO3Cl2 crystallize in the monoclinic space group P21/m with unit cell parameters a=5.0472(6) Å, b=6.6325(9) Å, c=8.3452(10) Å, β=105.43(1)°, Z=2. Co2TeO3Br2 crystallize in the orthorhombic space group Pccn with unit cell parameters a=10.5180(7) Å, b=15.8629(9) Å, c=7.7732(5) Å, Z=8. The crystal structures were solved from single crystal data, R=0.0328 and 0.0412, respectively. Both compounds are layered with only weak interactions in between the layers. The compound Co2TeO3Cl2 has [CoO4Cl2] and [CoO3Cl3] octahedra while Co2TeO3Br2 has [CoO2Br2] tetrahedra and [CoO4Br2] octahedra. The Te(IV) atoms are tetrahedrally [TeO3E] coordinated in both compounds taking the 5s2 lone electron pair E into account. The magnetic properties of the compounds are characterized predominantly by long-range antiferromagnetic ordering below 30 K.