Mixed-valence compounds based on heterometallic-oxo-clusters containing Sb(iii,v): crystal structures and proton conduction

Abstract

Isostructural mixed-valence compounds H9.2[Co(H2O)6]{M0.5(H2O)3.5{M’(H2O)4[SbVO6[Co4.2(H2O)5SbIII6(μ3-O)2(tta)6]]}}2·nH2O (M = Co, M’ = Co, n = 9 (1); M = Cd0.39/Co0.61, M’ = Cd0.24/Co0.76, n = 7 (2)) were synthesized. The proton conductivity of 2 is 1.42 × 10−3 S·cm−1 at 85 °C and 98% RH.

Synthesis and Properties of Cobalt/Nickel-Iron-Antimony(III, V)-Oxo Tartrate Cluster-Based Compounds

“…The above XPS results are in agreement with those reported in the literature, which further confirms the coexistence of +3 and +5 valence Sb atoms and +2 and +3 valence Fe atoms in 2 and 4 [23,24]. Furthermore, to the best of our knowledge, this is one of the few examples of heterometallic antimony-oxo clusters containing mixed valence Sb(III, V) [19,21].…”

“…Figure 4 further compares the structure of compound 2 with that of compound {M0.5(H2O)3.5{M'(H2O)4[Sb V O6[Co4.2(H2O)3Sb III 6(µ3-O)2(tta)6]}} 5.6− (M = Cd0.39/Co0.61, M' = Cd0.24/Co0.76, abbreviated as {Cd[SbCo]}) we just reported [21]. As can be seen in Figure 4a, the metal in the intermediate sandwich portion has been changed from the original {Sb V O6Co3Co(4)Co0.2(7)} in {Cd[SbCo]} to {Sb V 1/3Fe III 2/3O6Fe3Co2(Fe0.5( 5))2Fe II 1/3(4)} in 2.…”

“…In previous work, we have demonstrated that such antimony tartrate cluster-based compounds have the potential to act as proton conducting materials [15,19,21]. Given that compounds 2 and 4 can be stabilized in water, we evaluated the proton conductivity of columnar powder samples of the two compounds at different temperatures with a relative humidity of 98%.…”

“…Molecules 2024, 29, 591 2 of 13 To date, potassium antimony tartrate has been extensively combined with transition metal ions to form a range of transition-metal-antimony-oxo tartrate cluster-based structures with different structural types. In term of properties, however, mostly only the magnetic behavior has been investigated as shown in Table S1 [13][14][15][16][17][18][19][20][21]. From the structure point of view, the clusters adopt either sandwich or bowl configurations.…”

“…In bilayer-sandwiched compounds, the intermediate portion is occupied by the {MSb 3 } 2 (M = Co, Ni, Cu, Ni or Cr) layer (e.g., in Na 4 [Cu 2 Sb 12 (µ 3 -O) 6 (µ 3 -OH) 2 (µ 4 -O) 3 (tta) 6 ]•19H 2 O) [14,16,18]. By contrast, the intermediate layer of monolayer ones is generally occupied by {MO 6 M' 3 M" n } (M = V, Mn, Fe, Cu, Sb(V); M' = Mn, Fe, Co, Cu; M" = Mn, Fe, Co, Cu, Cd), where M is the center metal ion, M' are the three metal ions surrounding M and M" are the peripheral metal ions [13][14][15][16][17][19][20][21]. Notably, the vast majority of the center metal ions M are a transition metal ion (e.g., in (H 4 TPOM)[Fe III 4 Mn 3 Sb 6 (µ 4 -O) 6 (µ 3 -O) 2 (L-tta) 6 (H 2 O)]•16H 2 O, TPOM = tetrakis(4-pyridyl-oxymethylene)-methane) [17], while it is rarely occupied by Sb(V) (e.g., in H 5 {ACd(H 2 O) 6 [A(H 2 O) 3 Co 3 Sb V Sb III 6 (µ 3 -O) 8 (Ltta) 6 ]}•7H 2 O (A = Cd 0.5 + Co 0.5 )) [19,21].…”