Hydrothermal assembly strategy for the construction of oxygen‐bridging lanthanide‐substituted bilacunary Keggin‐type germanotungstate tetramers encapsulating [W3O12]6− connector

Abstract

AbstractUnder the hydrothermal condition and presence of organic amines, incorporating lanthanide (Ln) ions into monolacunary Keggin‐type germanotungstate precursor resulted in the formation of two new complex clusters formulated as H17(H2en)5[K3(H2O)(GeW10O37TbOTb)4(μ6‐W3O12)] ⋅ 45H2O (GeW‐Tb) and H22(H2en)3[K2(GeW10O37EuOEu)4(H2O)(μ6‐W3O12)] ⋅ 44H2O (GeW‐Eu) (en=ethylenediamine), which have been structurally characterized by elemental analyses, ICP analysis, IR spectra, thermogravimetric analysis, bond valence sum calculations and single‐crystal X‐ray diffraction. The most prominent structural feature of GeW‐Eu and GeW‐Tb revealed an unprecedented oxygen‐bridging Ln‐substituted bilacunary Keggin‐type germanotungstate tetramers encapsulating [W3O12]6− connector. What's more interesting is that a versatile library of linkable units including bilacunary germanotungstate [α‐GeW10O37]10−, internal oxo group between two Ln ions, as well as central tritungstate intermediate [W3O12]6− are all generated in situ thanks to the potential promotion of hydrothermal reaction system. In particular, the possible assembly mechanism for the complex clusters is proposed, and their solid‐state photoluminescence properties are also discussed in detail. To our knowledge, both [α‐GeW10O37]10− and [W3O12]6− intermediates are the highly robust POM building blocks that were first discovered. The studies highlight the structural diversity of Ln‐substituted germanotungstates and provide a new direction in the design of other functional germanotungstate based POMs in the future.