Self-Assembly of Ln(III)-Containing Tungstotellurates(VI): Correlation of Structure and Photoluminescence

The generation of five types of Ln(III)-containing tungstotellurates(VI), dimeric (DMAH)₁₂Na₂[H₁₀(WO₂){Ln(H₂O)₅(TeW₁₈O₆₅)}₂]·nH₂O (abbreviated as {Ln₂Te₂W₃₇}; Ln = Eu, Gd, or Tb; DMAH = dimethylammonium), tetrameric (DMAH)₂₁Na₇[H₁₆{Ln(H₂O)₅(TeW₁₈O₆₄)}₄]·nH₂O (abbreviated as {Ln₄Te₄W₇₂}, Ln = Eu or Gd), 2:2 dimeric (DMAH)₁₂[H₆{Tb(H₂O)₃(TeW₁₇O₆₁)}₂]·25H₂O (abbreviated as {Tb₂Te₂W₃₄}), 1:1 monosubstituted (DMAH)₇Na₂[H₂Tb(H₂O)₄(TeW₁₇O₆₁)]·21H₂O (abbreviated as {TbTeW₁₇}), and three-dimensional polymer (DMAH)₂[HTb(H₂O)₄{TeW₆O₂₄}]·14H₂O (abbreviated as {TbTeW₆}_n), provides insight into the rich condensation chemistry of lacunary and other Dawson-type polyoxometalates. The pH and the type of Ln³⁺ source both dictate which of these new complexes form. To our knowledge, {Ln₄Te₄W₇₂} is the highest-nuclearity tungstotellurate to date, and {Tb₂Te₂W₃₄} and {TbTeW₁₇} contain the first lacunary {TeW₁₇O₆₁}. Electrospray ionization mass spectra analyses indicate that the Dawson-like building blocks, {TeW₁₈O₆₅} and {TeW₁₇O₆₁}, found in solid structures are also present in solution. The intense photoluminescence (characteristic green emission) of {TbTeW₆}_n, 100× greater than those of {Tb₂Te₂W₃₇}, {Tb₂Te₂W₃₄}, and {TbTeW₁₇}, is explained by analysis of all 4 X-ray structures and multiple structure-intensity correlations.