Ag^IISO₄: A Genuine Sulfate of Divalent Silver with Anomalously Strong One‐Dimensional Antiferromagnetic Interactions

Abstract

Black AgSO4, synthesized for the first time by a displacement reaction, differs considerably from anhydrous sulfates of its Group 11 congeners: it has a very small electronic band gap (ca. 0.2 eV) and an anomalously strong one‐dimensional antiferromagnetic ordering ( J≈10 meV per Ag), which persists up to the onset of its thermal decomposition at about 120 °C. Ag gray, O red, S yellow.

Silverland: the Realm of Compounds of Divalent Silver—and Why They are Interesting

“…Moreover, in 2010, my laboratory was among those which greatly benefited from large structural funds coming from the European Union (CEPT project). The combined experimental/theoretical team (senior researcher Dr. P. Leszczyński; postdoctoral associates Dr. M. Derzsi, Dr. A. Budzianowski; PhD students P. Malinowski, D. Kurzydłowski, and several MSc students) focused their attention on compounds of Ag 2+ in F [61,62], O [63,64], N [65], and Cl [66] environment, by reinvestigating several poorly known systems and preparing or theoretically hypothesizing a few novel ones. The continued funding was later assured by the newly formed (2010) national state agency for funding of scientific research, Polish National Science Center (NCN), via grants OPUS and HARMO-NIA, with more enthusiastic young researchers onboard (P. Połczyński, T. Gilewski, T. Michałowski, J. Gawraczyński, A. Grzelak, and others).…”

“…Indeed, the first preparation of AgSO 4 was achieved in 2010 by P. Malinowski [64]. This compound showed a range of peculiar properties, but the most important one in the context of Ag 2+ research was the observation of the welldeveloped maximum of the magnetic susceptibility.…”

Chemistry of silver(II): a cornucopia of peculiarities

“…This means that the unpaired electron density at four F ligands surrounding silver is 0.4 µ B , comparable with that at the central Ag(II) cation. Another remarkable example is that of antiferromagnetic AgSO 4 [25]; here Ag(II) preserves the absolute magnetic moment of only ca 0.42 µ B while the absolute magnetic moment on O atoms reaches up to 0.09 µ B (recall: these 'oxide anions' are not free but they are covalently bound to sulfur atom!). The corresponding values for Cu(II) sulfate are: 0.80 µ B (Cu) and up to 0.03 µ B (O) [25].…”

“…Another remarkable example is that of antiferromagnetic AgSO 4 [25]; here Ag(II) preserves the absolute magnetic moment of only ca 0.42 µ B while the absolute magnetic moment on O atoms reaches up to 0.09 µ B (recall: these 'oxide anions' are not free but they are covalently bound to sulfur atom!). The corresponding values for Cu(II) sulfate are: 0.80 µ B (Cu) and up to 0.03 µ B (O) [25]. Strong spin polarization is seen even in such systems where the non-metal cannot attain large magnetic moment due to symmetry constraints.…”

“…The great majority of (even 'magnetically dense' i.e. Ag(II)-rich) compounds form lattices with rather isolated Ag(II) [25]. Red and dark blue colours denote maxima of alpha and beta density, respectively.…”