dl-Serine Covalently Ornamented and Ln 3+ -Incorporated Arsenotungstates with Fast-Responsive Photochromic and Photoinduced Luminescent Switchable Behaviors.

Three isostructural dl-serine covalently functionalized and multinuclear lanthanide (Ln 3+ )-embedded arsenotungstates, K 2 [{As 4 W 44 O 137 (OH) 18 (H 2 O) 2 (dl-Ser) 2 }{Ln 2 (H 2 O) 4 (dl-Ser)} 2 {Ln(H 2 O) 7 } 2 ]·70H 2 O (Ln = Sm ( 1 ), Eu ( 2 ), and Gd ( 3 ); dl-Ser = C 3 H 7 NO 3 ), were prepared, where the centrosymmetric [{As 4 W 44 O 137 (OH) 18 (H 2 O) 2 (dl-Ser) 2 }{Ln 2 (H 2 O) 4 (dl-Ser)} 2 ] 8- polyanion consists of two {As 2 W 19 O 59 (OH) 8 (H 2 O)} 6- fragments, integrated with a two-dl-serine-ornamented [W 6 O 23 (OH) 2 (dl-Ser) 2 {Ln 2 (H 2 O) 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 Sm 3+ and Eu 3+ 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.