Synthesis and Structural Characterization of ... - Jacobs University

Chapter 3
Published Results
Ce, Pr, Nd, Sm, Ho, Yb and Y, and also for Ce 4+ , all synthesized by reaction of the lanthanide
ions with Na 2 WO 4 in hot aqueous (pH 6.5−7.5) solution. The structure of the D 4d
[Ln(W 5 O 18 ) 2 ] n− polyanions consist of two monolacunary Lindqvist based fragments [W 5 O 18 ] 6-
encapsulating a central metal ion exhibiting a square-antiprismatic coordination. Yamase et al.
reported the crystal structures of the Pr, Nd, Dy, Sm, Eu, Gd and Tb derivatives with different
types of alkali counter cations. 7 The lanthanum analogue [La(W 5 O 18 ) 2 ] 9− was reported in
2005, 8 and also the actinide analogues [Th(W 5 O 18 ) 2 ] 8− and [U(W 5 O 18 ) 2 ] 8− have been studied
crystallographically. 5b,9 Very recently our group reported on the synthesis and solid state
structure of the yttrium-derivative [YW 10 O 36 ] 9– as well as its solution properties by 183 W and
89 Y NMR. 10 Very recently, Cao and coworkers reported on a pentadecatungstate ring capped
by two Ce 3+ ions. 11
The isopolyanion family [Ln III W 10 O 36 ] 9– , (Ln = Pr, Nd, Sm, Eu, Tb, Dy), has shown high
luminescence quantum efficiency. 12 The decatungstoterbate [Tb(W 5 O 18 ) 2 ] 9− showed greenemissive
luminescence. 7h Furthremore, Griffith and co-workers studied the
lanthanoisopolytungstates [Ln III W 10 O 36 ] 9– , (Ln = Y, La, Ce, Pr, Sm, Eu, Gd, Dy, Er, Lu), as
calalytic oxidants with H 2 O 2 for alcohol oxiditions and alkene epoxidations. 5b This provides
an impetus to prepare other, novel isopolyanion structures coordinated to lanthanide ions.
Herein we report on the synthesis of a novel class of 22-isopolytungstates {W 22 }
coordinated to two external lanthanide ions, [Ln 2 (H 2 O) 10 W 22 O 71 (OH) 2 ] 8− (Ln 3+ = La (1), Ce
(2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), Yb (8), Lu (9)) and yttrium,
[Y 2 (H 2 O) 10 W 22 O 71 (OH) 2 ] 8- (10).
3.A.1.2. Synthesis
Na 2 La 2 [La 2 (H 2 O) 10 W 22 O 72 (OH) 2 ]·44H 2 O (NaLa-1)
A sample of 10.00 g of Na 2 WO 4·2H 2 O (30.3 mmol) was dissolved in 20 mL H 2 O, followed
by dropwise addition of a solution of 1.02 g of LaCl 3·7H 2 O (2.8 mmol) in 5 mL H 2 O. Then
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