A new manganese gallium phosphate, Mn
3(H
2O)
6Ga
4(PO
4)
6, has been synthesized under hydrothermal conditionsat 150
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C and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, magnetic susceptibility,and electron paramagnetic resonance (EPR) spectroscopy. It crystallized in the monoclinic space group,
P2
1/
n,with
a = 8.9468(4) Å,
b = 10.1481(5) Å,
c = 13.5540(7) Å,
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= 108.249(1)
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, and
Z = 2. The compound isunusual in that it is not only the first nonorganically templated MnGaPO phase but also the first instance whereedge-shared trinuclear manganese-oxygen clusters are encapsulated in a metal phosphate lattice. The trimer involvesa central Mn(H
2O)
4O
2 octahedron, which links to two Mn (H
2O)
2O
4 octahedra at trans edges. The Mn
3(H
2O)
6O
8clusters reside in tunnels built from GaO
5 trigonal bipyramids and PO
4 tetrahedra. Our magnetic study revealedthat superexchange interactions occurred between the neighboring Mn
II centers. A good fit of the magneticsusceptibility data for the isolated trimers was obtained by using a derived expression based on Van Vleck'sequation. Unlike all existing linear trinuclear Mn
II complexes, the
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T product in the range 8-4 K remains at aconstant value corresponding to one spin
S =
5/
2 per three Mn
II centers. The Curie behavior at such low temperatureshas been confirmed by EPR data. According to the thermogravimetric analysis/differential thermal analysis (TGA/DTA) results, the title compound is thermally stable up to ca. 200
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C.