Silver(ii) triflate with one-dimensional [Ag(ii)(SO3CF3)4/2]∞ chains hosting antiferromagnetism

Abstract

Silver(II) triflate, previously reported by Leung et al. in 1979 (Can. J. Chem., 1979, 57, 326–329), crystallizes in a triclinic P cell with a = 4.9117(11) Å, b = 5.1136(10) Å, c = 11.033(3) Å, α = 79.955(14)°, β = 75.771(16)°, γ = 61.571(17)° and V = 235.68(10) ų and is isomorphous to Cu(SO₃CF₃)₂. The compound has a layered structure with an interlayer separation of 10.67 Å; the van der Waals gaps open between the CF₃ groups from neighbouring sheets. Ag(II) is coordinated by six O atoms in the form of an elongated octahedron; the adjacent Ag²⁺ cations are linked via –OSO– bridges; direct –O– bridges are absent. The [Ag(II)(SO₃CF₃)₂]_∞ layers consist of one-dimensional chains which interact weakly with each other via longer Ag⋯OSO–Ag contacts. This results in a 1D rather than 2D antiferromagnetic ordering, which can be described via the Bonner–Fisher model with a superexchange constant, J_intra-chain, of 104 K (9.0 meV) per pair of interacting Ag²⁺ cations. The magnetic ordering persists even at room temperature leading to a broad ESR signal with g = 2.199. DFT calculations confirm the 1D character of electronic structure and antiferromagnetism residing within the [Ag(II)(SO₃CF₃)_4/2]_∞ chains with a |J_inter-chain|/|J_intra-chain| ratio of ∼10⁻³ to 10⁻². The calculated indirect bandgap at the Fermi level of ∼1 eV opens between rather flat valence and conduction bands, which are predominated by contributions from Ag and O atoms. Ag(SO₃CF₃)₂ is extremely sensitive to moisture and decomposes instantly when exposed to atmosphere. When dry, it rapidly decomposes thermally above 120 °C, but its slow exothermic decay to AgSO₃CF₃ takes place even at room temperature. Silver(II) triflate is also photosensitive and irradiating it with a 632.8 nm laser radiation at a power greater than 0.17 mW leads to its decomposition to Ag(I) triflate and Ag(I)₂S₂O₇.