Integration of Ln-sandwich POMs into molecular porous systems leading to self-assembly of metal-POM framework materials

Reactions of lacunary polyoxometalate (POM), transition-metal (TM), and lanthanide-metal (Ln) cations with the assistance of additional small organic molecules under hydrothermal conditions led to the formation of a group of metal-POM frameworks (MPFs) with nanospaces: [Cu(enMe)(2)](13){Ln(SiW11O39)(2)}(2)center dot xH(2)O [Ln = Ho3+ (compound 1), Dy3+ (compound 2), Eu3+ (compound 3), Er3+ (compound 4), Sm3+ (compound 5), Pr3+ (compound 6); x = 18 for 1, 5, 6; x = 20 for 2, 3, 4; enMe = 1,2-diaminopropane). Single-crystal X-ray diffraction analyses reveal that all the compounds are composed of two monovacant POMs, which are linked by one Ln(3+) ion into a dimeric structure. The dimeric structure acts as an inorganic polydentate ligand coordinated with Cu2+ ions, which results in 3D MPFs with two channels. As the individual components integrated in the MPF materials posess fluorescent and magnetic properties, the luminescence properties and magnetic behavior of the resulting MPFs were measured.