![A Unique Two-Dimensional Silver(II) Antiferromagnet Cu[Ag(SO4)2] and Perspectives for Its Further Modifications](https://chemistry-europe.onlinelibrary.wiley.com/cms/asset/4fe37e96-f25a-4ba6-90f8-10b05b032cf3/chem202302042-toc-0001-m.png)
CuAg(SO4)2, a novel mixed-metal sulfate, shows a layered structure, with [Ag(SO4)2]2− sublattice (shown) hosting strong antiferromagnetic interactions. Calculations suggest that copper site could easily be changed for other small divalent cations, giving rise to a new family of two-dimensional magnetic materials.
Abstract
Copper(II) silver(II) sulfate crystallizes in a monoclinic CuSO4-related structure with P21/n symmetry. This quasi-ternary compound features Ag(SO4)2 2− layers, while the remaining cationic sites may be occupied either completely or partially by Cu2+ cations, corresponding to the formula of (Cu x Ag1−x )[Ag(SO4)2], x=0.6−1.0. CuAg(SO4)2 is antiferromagnetic with large negative Curie-Weiss temperature of −140 K and shows characteristic ordering phenomenon at 40.4 K. Density functional theory calculations reveal that the strongest superexchange interaction is a two-dimensional antiferromagnetic coupling within Ag(SO4)2 2− layers, with the superexchange constant J 2D of −11.1 meV. This renders CuAg(SO4)2 the rare representative of layered Ag2+-based antiferromagnets. Magnetic coupling is facilitated by the strong mixing of Ag d(x 2−y 2) and O 2p states. Calculations show that M2+ sites in MAg(SO4)2 can be occupied with other similar cations such as Zn2+, Cd2+, Ni2+, Co2+, and Mg2+.