Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH
2)
3]
4[{XW
12O
40
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Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH
2)
3]
4[{XW
12O
40}{Cu
2(pic)
4}]·[Cu
2(pic)
4(H
2O)]
2·6H
2O [X = Si (
1), Ge (
3)] and [C(NH
2)
3]
8[{SiW
12O
40}
2{Cu(pic)
2}
3{Cu
2(pic)
4(H
2O)}
2]·8H
2O (
2). The three compounds show a pronounced two-dimensional character owing to the structure-directing role of guanidinium. In
1 and
3, layers of [{XW
12O
40}{Cu
2(pic)
4}]
n4n− hybrid POM chains and layers of [Cu
2(pic)
4(H
2O)] complexes and [C(NH
2)
3]
+ cations pack alternately along the
z axis. The hydrogen-bonding network established by guanidinium leads to a trihexagonal tiling arrangement of all copper(II)-picolinate species. In contrast, layers of [C(NH
2)
3]
+-linked [{SiW
12O
40}
2{Cu(pic)
2}
3]
n8n− double chains where each Keggin cluster displays a {Cu
2(pic)
4(H
2O)} moiety pointing at the intralamellar space are observed in
2. The thermal stability of
1–
3 has been studied by thermogravimetric analyses and variable temperature powder X-ray diffraction. Compounds
1 and
3 undergo single-crystal to single-crystal transformations promoted by reversible dehydration processes and the structures of the corresponding anhydrous phases
1a and
3a have been established. Despite the fact that the [Cu
2(pic)
4(H
2O)] dimeric complexes split into [Cu(pic)
2] monomers upon dehydration, the packing remains almost unaltered thanks to the preservation of the hydrogen-bonding network established by guanidinium and its associated Kagome-type lattice. Splitting of the dimeric complexes has been correlated with the electron paramagnetic resonance spectra.
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