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In Situ Recrystallization of Polyoxometalates: From 0D Architectures to 2D Inorganic–Organic Hybrids



The compound (4-H2pya)3[Al(OH)6Mo6O18]·5H2O (1) transforms into two 2D hybrid species (4-Hpya)[(4-Hpya)Ln(H2O)5]2[Al(OH)6Mo6O18]2·13H2O {Ln = Ce (2), La (3); 4-Hpya = 3-(4-pyridyl)acrylic acid} in the mother liquor through crystal dissolution and recrystallization; this represents a rare example of in situ recrystallization involving polyoxometalate crystal systems. All compounds were characterized by elemental analysis, IR and UV/Vis spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 1 is a 0D architecture consisting of protonated 4-H2pya ligands and [Al(OH)6Mo6O18]3– polyoxoanions, which are connected through hydrogen-bonding and electrostatic interactions. Isostructural compounds 2 and 3 crystallize in the triclinic crystal system, space group Pequation image, and exhibit a unique 2D framework composed of [Al(OH)6Mo6O18]3– polyoxoanions and Ln-4-Hpya coordination complexes with a rare (3,4)-connected net. The magnetic properties of compound 2 were studied by measuring its magnetic susceptibility in the temperature range 2.0–300.0 K.