Multi-Ce III -Inserted Phospho(III)tungstate Containing Three Building Units with Prominent Peroxidase-Mimicking Activity for Detecting l-Cysteine.

An attractive isonicotinic acid-ornamented octa-Ce III -inserted phospho(III)tungstate [H 2 N(CH 3 ) 2 ] 6 Na 8 [Ce 8 (H 2 O) 30 W 8 Na 2 O 20 (INA) 4 ][HP III W 4 O 17 ] 2 [HP III W 9 O 33 ] 4 ·30H 2 O ( 1-Ce ) (HINA = isonicotinic acid) has been isolated through the deliberately designed one-step assembly strategy, in which the HPO 3 2- heteroanion template was introduced into the Ce 3+ /WO 4 2- system in the presence of HINA. The polyoxoanion of 1-Ce consists of two identical [Ce 4 (H 2 O) 15 W 4 NaO 10 (INA) 2 ][HP III W 4 O 17 ][HP III W 9 O 33 ] 2 } 7- subunits linked by Ce-O-W bonds. The polyoxoanion exhibits three kinds of polyoxotungstate building blocks [W 4 NaO 20 (INA) 2 ] 17- , [HP III W 4 O 17 ] 6- , and [HP III W 9 O 33 ] 8- , in which [W 4 NaO 20 (INA) 2 ] 17- and [HP III W 4 O 17 ] 6- building units can be considered as seeds driven by the coordination of additional Ce 3+ ions to induce aggregation of [HP III W 9 O 33 ] 8- fragments. Furthermore, 1-Ce possesses high peroxidase-like activity and can oxidize 3,3',5,5'-tetramethylbenzidine in the presence of H 2 O 2 with a turnover rate of 6.20 × 10 -3 s -1 . Because l-cysteine (l-Cys) can reduce oxTMB to TMB, the detection of l-Cys was established based on the 1-Ce -based H 2 O 2 colorimetric biosensing platform with the linear range of 5-100 μM and the limit of detection of 4.28 μM. This work not only can expand the scientific research studies on coordination chemistry and materials chemistry of rare-earth-inserted polyoxotungstates but also can provide practical application possibility in clinical diagnosis using liquid biopsy.