Structure analysis indicates that
1 is composed of 1D linear chainlike anion [{Ln(H
2O)
7}
2{As
4W
44O
137(OH)
18(H
2O)
2(DL-Ser)
2}{La
2(H
2O)
5(DL-Ser)}
2]
2−, two K
+ cations and 65 lattice water molecules. Specifically, this 1D framework is built up of the tetra-nuclear Ln
3+ implanted DL-serine covalently modified arsenotungstate polyoxoanion [{As
4W
44O
137(OH)
18(H
2O)
2(DL-Ser)
2}{La
2(H
2O)
5(DL-Ser)}
2]
8– (
1a) (
Fig. 1a). Regardless of the insertion of La
3+ ions, the polyoxoanion
1a can be considered as a double DL-Ser groups covalently modified arsenotungstate cluster [As
4W
44O
137(OH)
18(H
2O)
2(DL-Ser)
2]
18‒, which consists of two distorted {As
2W
19O
59(OH)
8(H
2O)}
6‒ building blocks linked together by a double DL-Ser ligands functionalized [W
6O
23(OH)
2(DL-Ser)
2]
14‒ fragment (
Fig. 1b). In the structure of
1a, the {As
2W
19O
59(OH)
8(H
2O)}
6‒ building blocks are distinctly different from the precursor [As
2W
19O
67(H
2O)]
14‒ ({As
2W
19}) (Fig. S1 in Supporting information), and the opening angle in
1a is obviously greater than that of the {As
2W
19} precursor. This means that the {As
2W
19} precursor undergo significant dissociation recombination or torsion deformation during the reaction process. Remarkably, the central part {WO
5(H
2O)} group in {As
2W
19} precursor changed from {WO
5(H
2O)} to {WO
6} in the assembly process of
1a, also opening the As⋯W({WO
6})⋯As angle. As a result, the As⋯As distance in
1 was 8.114(19) Å, which is obviously longer than the As⋯As distance in {As
2W
19} precursor of 6.522(11) Å (Fig. S1), as well as the significantly larger angle As−W({WO
6})−As(171.88(9)°) compared to the angle of 110.01(5)° in {As
2W
19} precursor (Fig. S1), and this phenomenon has been reported before [
28-
30]. At the same time, the centrosymmetric Z-shaped [W
6O
23(OH)
2(DL-Ser)
2]
14‒ segment (Fig. S2a) is made up of a pair of serine covalently modified {W
2O
9(DL-Ser)}
7‒ groups, in which W1 and W2 (W3 and W4) atoms are connected by a chelating DL-Ser ligand and a
μ2–O atom, fused together by a corner-sharing {W
2O
5(OH)
2} segment (
Fig. 1c). Also, the [W
6O
23(OH)
2(DL-Ser)
2]
14‒ segment is viewed as a pair of DL-serine covalently modified {W
3O
11(OH)(DL-Ser)}
6– groups connected through a
μ2‒O atom in the form of a common vertex
μ2‒O atom from another perspective (Fig. S2b in Supporting information). Alternately, the polyoxoanion [{As
4W
44O
137(OH)
18(H
2O)
2(DL-Ser)
2}{La
2(H
2O)
5(DL-Ser)}
2]
8‒ can also be viewed as a tetramer established by two [B-
α-AsW
9O
29(OH)
4]
5‒ subunits, two [B-
α-AsW
9O
28(OH)
4(H
2O)]
3‒ subunits, and a central [{W
8O
43(OH)
2(DL-Ser)
2}{La
2(H
2O)
5(DL-Ser)}
2]
32‒ group (Fig. S3 in Supporting information). Moreover,
1a is further stabilized by two embedded [La
2(H
2O)
5(DL-Ser)]
5+ groups, which is connected into 1D linear chainlike structure
via two peripheral La
3+ ions (
Fig. 1d).