Abstract: In this paper we report the successful hydrothermal synthesis of the two inorganic- organic hybrid assemblies H0.87{Na(H2O)3[Dy(PDA(H2O)2]3(BW12O40)0.87(SiW12O40)0.13}•11H2O (1) and H0.87{Na(H2O)3[Ho(PDA)(H2O)2]3 (BW12O40) 0.87(SiW12O40)0.13}•10H2O (2) (H2PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized using elemental analyses, Fourier transform infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Structural characterizations by single-crystal X-ray diffraction reveals that these hybrids are isostructural including [BW12O40] 5‒ Keggin-type polyoxometalates (actually containing 87% B and 13% Si based on refinement of the crystal structures) connected by three lanthanoids to yield discrete trinuclear lanthanoid clusters. These discrete molecules are further packed into 3D supramolecular assemblies by means of hydrogen-bonding and anion–π interactions. 1 and 2 are two examples of a relatively small number of inorganic-organic hybrid POMs containing the PDA ligand based on a CSD search (CSD version 5.40 updated to November 2018). The temperature dependences of χmT for 1 and 2 are considered. Magnetic studies reveal that 1 exhibits typical single‐molecule magnet (SMM) behavior.

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