Ag_1+xTlO₂ (0.03 ≤ x ≤ 0.18), Novel Adaptations of the Delafossite Structure Type Featuring Subvalent Silver

Abstract

A family of novel variations of the delafossite type of structure, Ag1+xTlO2, was synthesized and characterized. For three members the crystal structures were solved and refined on single crystal data: Ag1+αTlO2 [α = 0.18, P$\bar{3}$m1, Z = 1, a = 3.40427(9), c = 6.1296(1) Å, R1 = 0.033, 126 independent reflections]; Ag1+βTlO2 [β = 0.09, R$\bar{3}$m, Z = 6, a = 3.40685(8), c = 37.5953(9) Å, R1 = 0.039, 214 independent reflections]; Ag1+γTlO2 [γ = 0.03, R$\bar{3}$m, Z = 9, a = 3.403(2), c = 56.67(3) Å, R1 = 0.038, 397 independent reflections]. Different from the conventional delafossite structure, part of the silver layers accommodate an excess of ca. 0.18 silver atoms per layer, thus generating a subvalent bonding state of silver. In accordance with the structural findings, the new silver oxthallates(III) are metallic conductors, and show reduced binding energies for the silver 3d5/2 states, compared to silver(I) oxide.

A Segregated, Partially Oxidized, and Compact Ag10 Cluster within an Encapsulating DNA Host

“…83,84 However, a wide range of these compounds has been synthesized with diverse ligands such as halides, oxides, thiols, peptides, and oligonucleotides. 56,85–90 The first reported example, Ag 2 F, and related compounds mimic bulk silver because they have high electrical conductivities at temperatures as low as 20 K. 91–93 Such metallic characteristics may develop because low-lying 5 s /5p states lie near the Fermi level and can accommodate excess electrons. 92,94 These complexes have relatively short silver–silver bond distances of 2.75–2.85 Å, as does the violet cluster.…”

“…The EXAFS spectrum supports a metal-like core because the 2.743 Å Ag–Ag bond length is similar to the 2.889 Å bond distance in metallic silver (Ag–Ag 1 in Table ). However, the shorter bond length for the cluster can also signify a partially oxidized core. , Subvalent silver complexes were once considered to be rare because the individual silvers have fractional oxidation states that conflict with basic bonding theories. , However, a wide range of these compounds has been synthesized with diverse ligands such as halides, oxides, thiols, peptides, and oligonucleotides. ,− The first reported example, Ag 2 F, and related compounds mimic bulk silver because they have high electrical conductivities at temperatures as low as 20 K. − Such metallic characteristics may develop because low-lying 5 s /5p states lie near the Fermi level and can accommodate excess electrons. , These complexes have relatively short silver–silver bond distances of 2.75–2.85 Å, as does the violet cluster . A partially oxidized core within the violet cluster is also supported by the average Ag–Ag coordination number and the overall cluster charge (Table ).…”