Synthesis and Structural Characterization of ... - Jacobs University

Chapter 3
Unpublished Results
Here we report the synthesis of three head-on complexes of germanotungstates [{Ln(-
CH 3 COO)(H 2 O) 2 (-GeW 11 O 39 )} 2 ] 12− (Ln = Eu (21), Gd (22), Lu(23)). All polyanions 21–23
were structurally characterized by single-crystal X-ray diffraction, FTIR spectroscopy,
thermogravimetric analysis (TGA), and multinuclear NMR spectroscopy ( 183 W, 13 C and 1 H)
for the diamagnetic analogue (Lu(23)).
3.B.3.2. Synthesis
The precursors K 6 Na 2 [-GeW 11 O 39 ]·13H 2 O and K 8 Na 2 [A--GeW 9 O 34 ]·25H 2 O used for the
synthesis of the reported species were synthesized according to the published procedures. 3
K 12 [(Eu(GeW 11 O 39 )(H 2 O)) 2 (-CH 3 COO) 2 ]·24H 2 O (K-21)
0.064 g of EuCl 3·6H 2 O was dissolved in 20 mL of 1M potassium acetate buffer at pH 4.8,
followed by the addition of 0.50 g of K 8 Na 2 [A--GeW 9 O 34 ]·25H 2 O. Then, the solution was
stirred and heated to 90 °C for 30 minutes. The solution was allowed to cool to room
temperature and then filtered. Slow evaporation of the solvent at room temperature for about
three days led to the formation of colorless crystals suitable for X-ray diffraction. These
crystals were isolated and air-dried (yield 0.68 g, 63 %). IR data for K-21: 1625(m), 1530(m),
1459(m), 1397(w), 1351(sh), 950(s), 893(s), 809(s), 779(sh), 746(w), 678(s), 615(sh), 526(m),
497(sh), 466(m), 446(w) cm -1 (see Figure 3.37). Anal. Calcd for K-21: K, 6.9; Ge, 2.1; W,
59.5; Eu, 4.5; C, 0.71; H, 0.86. Found: K, 6.6; Ge, 2.1; W, 60.2; Eu, 4.5; C, 0.75; H, 0.86.
K 12 [(Gd(GeW 11 O 39 )(H 2 O)) 2 (-CH 3 COO) 2 ]. 24H 2 O (K-22)
The same procedure as K-21 was followed, except for using 0.063 g GdCl 3·6 H 2 O. Yield:
o.671 g (62%). IR data for K-22: 1625(m), 1530(m), 1459(m), 1397(w), 1351(sh), 950(s),
893(s), 809(s), 779(sh), 746(w), 678(s), 615(sh), 526(m), 497(sh), 466(m), 446(w) cm -1 (see
Figure 3.37). Anal. Calcd for K-22: K, 6.9; Ge, 2.1; W, 59.9; Gd, 4.6; C, 0.71; H, 0.85.
Found: K, 6.8; Ge, 2.1; W, 61.2; Gd, 4.6; C, 0.76; H, 0.84.
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