First Dimethyltin-Functionalized Rare-Earth Incorporated Tellurotungstates Consisting of {B-α-TeWO} and {WO} Mixed Building Units.

The facile one-step assembly reaction of NaWO·2HO, Sn(CH)Cl, RE(NO)·6HO and KTeO in the presence of dimethylamine hydrochloride as an organic solubilizing agent in acidic aqueous solution resulted in a family of dimethyltin-functionalized rare-earth (RE) incorporated tellurotungstates consisting of {B-α-TeWO} and {WO} mixed building units [HN(CH)]NaH[RE(OH)(B-α-TeWO)Sn(CH)(WO)]·18HO [RE = Er (1), Yb (2), Ho (3), Y (4)]. The most striking structural characteristic of 1-4 is that they all contain a novel tetrameric S-shaped [RE(OH)(B-α-TeWO)Sn(CH)(WO)] moiety simultaneously including two pentavacant Keggin [B-α-TeWO] and two monovacant Lindqvist [WO] fragments connected by RE and dimethyltin linkers. To the best of our knowledge, such dimethyltin-functionalized RE-containing tellurotungstates have not been reported before. The visible or NIR solid-state emission spectra of 1 and 3 display the characteristic emission bands arising from Er and Ho centers. Moreover, various 1-Er/Yb co-doped samples were prepared by controlling different mass ratio of Er(NO)·6HO/Yb(NO)·6HO in the range of 0.96:0.04-0.02:0.98. In the visible region, the emission intensity of the 1-Er/Yb co-doped sample reaches the maximum at the mass ratio of Er(NO)·6HO/Yb(NO)·6HO being 0.40:0.60, and this observation is mainly derived from the fact that the Yb ions can sensitize the Er ions to enhance the emission intensity in the visible region. However, no such phenomenon for the 1-Er/Yb co-doped samples is seen in the NIR region. Besides, the upconversion spectra of the 1-Er/Yb co-doped samples were first observed. In addition, the thermal stabilities of 1-4 were also investigated on the crystalline samples and the thermal decomposition process of 1 has been deeply studied.