Two tetra-antimony(III)-bridged, sandwich-type 1 8-tungsto-2-arsenates (V), [(LSbIII)(4) (A-alpha-As (W9O34)-W-V)(2)](10-) (L = Ph (1), OH (2)), were prepared and fully characterized in the solid state and in solution. Both polyanions are stable in aqueous physiological medium for at least 24 h (at concentrations >= 2.5 x 10(-6) M). Despite the presence of an isostructural tetra-antimony(III) motif in 1 and 2, distinctly different antibacterial activity was observed for both polyanions. The minimum inhibitory concentrations (MIC) of 1 (7.8-62.5 mu g/mL) is lower than for any other organoantimony(III)-containing polyoxometalate reported to date.