Strong One‐Dimensional Antiferromagnetic Interactions of Silver(II) Ions in Silver Sulfate

Abstract

magnetic properties · oxides · silver · solid-state structures · sulfatesThe search for new compounds that contain elements in unusual oxidation states is worthwhile, since these compounds often exhibit novel and unconventional chemical and physical properties, for example, those observed in the superconducting Cu II,III oxides. [1] The dominant oxidation state of Ag is + 1 and only a few compounds with Ag in higher oxidation states have been synthesized to date. The situation is different for the other coinage metals, in that Cu, the lighter homologue of Ag, can easily adopt the oxidation state + 2, whereas the heavier homologue Au is mainly found with the oxidation state + 3. Ag 2+ forms stable complexes with a variety of nitrogen donor ligands, such as pyridine [2] or pyrazine (pyz). [3] Other examples of Ag II compounds are the binary fluoride AgF 2 and its complex salts, for example, Cs 2 AgF 4 , [4] which has recently attracted great interest since it orders ferromagnetically at low temperatures.[5] Among fluorides, even higher oxidation states of Ag are known, for example, Ag 3+ and Ag 4+ in KAgF 4[6] and Cs 2 AgF 6 , [7] respectively. Oxides containing Ag in an oxidation state higher than + 1 are very rare. The binary compound AgO is not a Ag II compound, but the diamagnetic mixed-valent compound Ag I Ag III O 2 . [8] Ag 3 O 4 is also a mixed-valent compound as indicated by the formula Ag II Ag III 2 O 4 , [9] whereas Ag 2 O 3 contains only Ag 3+ ions. [10] Malinowski et al. [11] recently reported the synthesis of black AgSO 4 , which has been obtained by a methathetic reaction of Ag(SbF 6 ) 2 + K 2 SO 4 in anhydrous HF at around À80 8C or by the reaction of AgF 2 with H 2 SO 4 at À35 8C. According to thermoanalytical studies, the product is metastable and decomposes above 120 8C with evolution of O 2 . The triclinic crystal structure of AgSO 4 contains planar rectangular AgO 4 units that are connected by SO 4 tetrahedra to form a three-dimensional network (Figure 1). The Ag-O distances within the AgO 4 units range from 2.09 to 2.20 , [12] as expected for a four-coordinate Ag 2+ ion, [9] thus suggesting that AgSO 4 is indeed a complex Ag II oxide. The two Ag(1)O 4 and Ag(2)O 4 units are significantly elongated along the twofold axes with O-O distances of 2.62 and 2.70 for the short edges and 3.30 and 3.34 for the long edges, respectively. The structural chemistry of the 4d ion Ag 2+ (4d 9 , S = 1/2) differs considerably from that of its 3d and 5d analogues Cu 2+ (3d 9 , S = 1/2) and Au 2+ (5d 9 , S = 1/2). This difference is most obvious when the sulfates are compared. The Ag 2+ ions in AgSO 4 display a rectangular coordination of O atoms, whereas the smaller Cu 2+ ions in CuSO 4 exhibit a distorted octahedral coordination; [13] it is clear that the Jahn-Teller effect is stronger for Ag 2+ than for Cu 2+ . In the structure of AuSO 4 , diamagnetic Au-Au dumbbells with short Au-Au distances of 249 pm are found, [14] thus reflecting the increasing tendency for the occurrence of metal-metal bonding down a gr...

A Unique Two‐Dimensional Silver(II) Antiferromagnet Cu[Ag(SO4)2] and Perspectives for Its Further Modifications

“…[24] In these oxyanionic salts, the Ag 2 + sites are connected via the oxo ligands which may transfer spin interactions quite effectively. However, most of the mentioned compounds are 1D antiferromagnets: for example AgSO 4 (À 18.7 meV), [17,25,26] KAg 3 (SO 3 F) 5 (À 19.1 meV), [23] Ag 2 Ag(SO 3 F) 4 (À 15.4 meV), [20,23] or Ag(SO 3 CF 3 ) 2 (À 9.0 meV). [22] Ag 2 + is present here in the square-planar coordination of four oxide ligands, indicating that d 9 -hole sits on d(x 2 À y 2 ) type orbitals.…”

Theoretical prediction of a graphene-like 2D uranyl material with p-orbital antiferromagnetism

“…61,62 In this work, by combining both bottom-up and GM structure search strategies, a novel graphene-like 2D uranyl material is computationally predicted to be highly stable, thus extending the design of graphene-like 2D materials to the domain of fblock actinides that are stable kinetically and thermodynamically. Furthermore, the 2D uranyl sheet features a rare type of 1D spin-1/2 Heisenberg chain with a long-range antiferromagnetic (AFM) spin order on the superoxido groups, [63][64][65][66] where there exists a new type of 2p p* -5f d -2p p* superexchange interaction. Most oen, the AFM order in crystals is caused by the superexchange interaction among the d-type AOs of transition metals via the p-type AOs of the ligands.…”

Relativistic Effects Stabilize Unusual Gold(II) Sulfate Structure via Aurophilic Interactions

“…Anhydrous copper sulfate CuSO 4 ( 1 ) is an antiferromagnetic white/light gray powder that adopts a rather unspectacular orthorhombic crystal structure (space group Pnma ) with formally six SO 4 2– units coordinating to a Cu 2+ center in a Jahn–Teller distorted CuO 6 octahedral environment. , In contrast, AgSO 4 ( 2 ) has only been synthesized very recently by Grochala and co-workers − and is a black powder consisting of antiferromagnetically coupled one-dimensional chains. It crystallizes within the triclinic P 1̅ space group.…”