Three isostructural dl-serine covalently functionalized
and multinuclear lanthanide (Ln3+)-embedded arsenotungstates,
K2[{As4W44O137(OH)18(H2O)2(dl-Ser)2}{Ln2(H2O)4(dl-Ser)}2{Ln(H2O)7}2]·70H2O (Ln = Sm (1), Eu (2), and Gd (3); dl-Ser = C3H7NO3), were prepared, where the centrosymmetric
[{As4W44O137(OH)18(H2O)2(dl-Ser)2}{Ln2(H2O)4(dl-Ser)}2]8– polyanion consists of two
{As2W19O59(OH)8(H2O)}6– fragments, integrated with a two-dl-serine-ornamented [W6O23(OH)2(dl-Ser)2{Ln2(H2O)4}2]8– segment.
In addition, the photochromic transformation of solid-state compounds 1–3 was observed from colorless to blue
after a UV illumination of 4 min, and the decay process lasted as
long as ∼20 h in the dark. The coloration kinetic half-life
(t
1/2) values of compounds 1, 2, and 3 were calculated to be 0.597,
0.920, and 0.723 min, respectively. Furthermore, the luminescent properties
and energy migration from arsenotungstates and organic chromophores
to Sm3+ and Eu3+ ions in 1 and 2 have been intensively investigated. Further analysis manifests
that 1 possesses an effective luminescent switchable
behavior, triggered by its fast-responsive photochromism effect.