1-D Chain Tungstotellurate Hybrids Constructed from Organic-Ligand-Connecting Iron-Lanthanide Heterometal Encapsulated Tetrameric Polyoxotungstate Units.

Abstract

A family of inorganic-organic hybrid one-dimensional (1-D) chain iron-lanthanide (Ln) heterometal encapsulated tungstotellurates [H2N(CH3)2]8K2Na4[Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2][Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]·50H2O [Ln = Eu3+ (1), Tb3+ (2), Dy3+ (3), Er3+ (4), HAc = acetate acid, H2pdca = 2,5-pyridinedicarboxylic acid] were prepared using a facile "one-pot" reaction. The molecular structures of 1-4 consist of an intriguing organic-ligand-connecting Fe-Ln heterometal inserted tetrameric unit [Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2][Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]14-. Appealingly, the tetrameric unit is composed of two sandwich-type subunits [Ln2(Ac)2(H2O)4Fe2(Hpdca)2(B-β-TeW9O33)2]8- and [Ln2(H2O)8Fe2(Hpdca)2(B-β-TeW9O33)2]6-, in which each sandwich-type subunit can be regarded as a derivative of two Ln-organic complexes substituting two external FeIII ions in the classic Krebs-type [Fe4(H2O)10(β-TeW9O33)2]4- fragment. Furthermore, adjacent tetrameric units are interconnected into a 1-D chain arrangement by Hpdca- bridges. 1-4 represent the first examples of Fe-Ln heterometal encapsulated tungstotellurates. Comprehensive magnetic measurements of 3 imply the possible single-molecule magnet properties in 3 with an estimated relaxation time τ0 ≈ 6.06 × 10-6 s at Hdc = 0 Oe and τ0 ≈ 6.97 × 10-5 s at Hdc = 1500 Oe. In addition, the solid-state photoluminescence spectra of 1 and 2 at room temperature exhibit the typical f-f transitions of Ln cations. The Commission International d'Eclairage (CIE) color coordinates of (0.540 24, 0.442 44) for 1 and (0.428 71, 0.428 30) for 2 along with the correlated color temperatures of 1995 and 3278 K, dominant wavelengths of 586 and 578 nm, and color purities of 95.09% and 57.27% for 1 and 2 are obtained.