Synthesis of thiophene-2,5-diphosphonic acid 2 is reported, and its use for synthesis of the original pristine materials Mn-2(O3P-C4H2S-PO3)center dot 2H(2)O 3 is reported. The structure of material 3 has been fully resolved from single-crystal X-ray diffraction. Mn-2(O3P-C4H2S-PO3)center dot 2H(2)O 3 crystallizes in a monoclinic cell (space group P2) with the following parameters: a = 11.60(1) angstrom, b = 4.943(5) angstrom, c = 19.614(13) angstrom, beta = 107.22 degrees. A noticeable feature of the structure of compound 3 is the orientation of the thiophene heterocycles that adopt two different orientations in two successive layers (along c). Thermal analysis of compound 3 indicates that the water molecules are easily removed from 160 to 230 C while the dehydrated structure is stable up to 500 degrees C. The dehydrated compound obtained from 3 can be rehydrated to give the polymorphic compound Mn-2(O3P-C4H2S-PO3)center dot 2H(2)O 4, which crystallizes in an orthorhombic cell (space group Pnam) with the following parameters: a = 7.5359(3) angstrom, b = 7.5524(3) angstrom, c = 18.3050(9) angstrom. The main difference between the structures of 3 and 4 arises from both the orientation of the thiophene rings (herringbone-type organization in 4) and the structure of the inorganic layers. The thiophene-2,5-diphosphonic acid moieties engaged in materials 3 and 4 adopt a different orientation likely due to rotation around the P-C bonds and via the dehydrated state 5, which is likely more flexible than the hydrated states. Study of the magnetic properties performed on compound 3 and 4 and on the dehydrated compounds Mn-2(O3P-C4H2S-PO3) 5 complemented by the structural study has permitted us to characterize the antiferromagnetic ground state of sample 3, a weak ferromagnetic component in sample 4, and complete paramagnetic behavior in sample 5.