Di-μ-methacrylato-bis[diaquabis(methacrylato)europium(III)] methacrylic acid disolvate

In the title centrosymmetric complex, [Eu2(C4H5O2)6(H2O)4]·2C4H6O2, the unique EuIII cation is coordinated by seven carboxylate O atoms from four methacrylate ligands and two water molecules in a slightly disorted tricapped trigonal–prismatic environment. Two EuIII ions are bridged by carboxylate groups, forming a dinuclear complex. The formula unit also contains two molecules of methacrylic acid. In the crystal structure, molecules are linked via intermolecular O—H⋯O hydrogen bonds, forming one-dimensional chains propagating along the b-axis direction

In the title centrosymmetric complex, [Eu 2 (C 4 H 5 O 2 ) 6 -(H 2 O) 4 ]Á2C 4 H 6 O 2 , the unique Eu III cation is coordinated by seven carboxylate O atoms from four methacrylate ligands and two water molecules in a slightly disorted tricapped trigonal-prismatic environment. Two Eu III ions are bridged by carboxylate groups, forming a dinuclear complex. The formula unit also contains two molecules of methacrylic acid. In the crystal structure, molecules are linked via intermolecular O-HÁ Á ÁO hydrogen bonds, forming one-dimensional chains propagating along the b-axis direction

S1. Comment
There has been considerable interest in the design and synthesis of supramolecular architectures (Yaghi et al., 1998;Millange et al., 2004 Å. These values are in good agreement with those found in an other closely related structure (Petrochenkova et al., 2002).
Two Eu III ions are bridged by carboxylate groups to create a discrete centrosymmetric dinuclear complex. In the crystal structure, complex molecules and solvated methacrylic acid molecules are linked via intermolecular O-H···O hydrogen bonds froming one-dimensional chains running along the b axis direction (Fig. 2).

S2. Experimental
The title complex was hydrothermally prepared from a mixture of Eu(NO 3 ) 3 . 6H 2 O (0.2 mmol), methacrylic acid (0.6 mmol), NaOH (0.6 mmol) and H 2 O (10 ml). The slurry was stirred for 30 min and heated at 393 K for 72 h in a Teflonlined stainless steel autoclave (25 ml) under autogenous pressure. After cooling to room temperature, the block-shaped crystals were washed with water and dried in air.

S3. Refinement
All H atoms were treated as riding, with C-H = 0.93-0.96 Å, O-H = 0.8199-1.011 (as found positions) Å, and U iso (H) = 1.2U eq (aryl C and O) or 1.5U eq (methyl C). The terminal C atoms of the methacrylate ligands and the methacrylic acid molecules have larger than normal anisotropic displacement parameters. This may be the effect from data collected at room temperature or the result of very slight disorder which has not been modelled.

Figure 1
The molecular structure showing displacement ellipsoids at the 30% probability level [symmetry code: (a) -x + 1,-y + 1,z]. Only the unique methacrylic acid of the symmetric unit has been shown.

Figure 2
The packing of the title compound. Dashed lines indicate hydrogen bonds.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.