Self-assembly of [B-SbW9O33]9- subunit with transition metal ions (Mn2+, Cu2+, Co2+) in aqueous solution: syntheses, structures and magnetic properties of sandwich type polyoxometalates with Subvalent Sb(III) heteroatom.

Rational self-assembly of Sb(2)O(3) and Na(2)WO(4), or (NH(4))(18)[NaSb(9)W(21)O(86)] with transition-metal ions (Mn(2+), Cu(2+), Co(2+)), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na(2)H(2)[Mn(2.5)W(1.5)(H(2)O)(8)(B-beta-SbW(9)O(33))(2)]32 H(2)O (1), Na(4)H(7)[Na(3)(H(2)O)(6)Mn(3)(mu-OAc)(2)(B-alpha-SbW(9)O(33))(2)]20 H(2)O (OAc=acetate anion) (2), NaH(8)[Na(2)Cu(4)Cl(B-alpha-SbW(9)O(33))(2)]21 H(2)O (3), Na(8)K[Na(2)K(H(2)O)(2){Co(H(2)O)}(3)(B-alpha-SbW(9)O(33))(2)] 10 H(2)O (4), and Na(5)H[{Co(H(2)O)(2)}(3)W(H(2)O)(2)(B-beta-SbW(9)O(33))(2)]11.5 H(2)O (5). These structures are determined by using the X-ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two [B-beta-SbW(9)O(33)](9-) building units, whereas 2, 3, and 4 consist of two isomerous [B-alpha-SbW(9)O(33)](9-) building blocks, which are all linked by different transition-metal ions (Mn(2+), Cu(2+), or Co(2+)) with different quantitative nuclearity. It should be noted that compound 2 represents the first one-dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate-bridging ligands. Additionally, 3 is constructed from sandwiched anions [Na(2)Cu(4)Cl(B-alpha-SbW(9)O(33))(2)](9-) linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion [{Co(H(2)O)(2)}(3)W(H(2)O)(2)(B-beta-SbW(9)O(33))(2)](6-) linked by Co(2+) and Na(+) ions. EPR studies performed at 110 K and room temperature reveal that the metal cations (Mn(2+), Cu(2+), Co(2+)) reside in a square-pyramidal geometry in 2, 3, and 4. The magnetic behavior of 1-4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J=-0.552 cm(-1) in 2.