Self-Assembly of a Family of Isopolytungstates Induced by the Synergistic Effect of the Nature of Lanthanoids and the pH Variation in the Reaction Process: Syntheses, Structures, and Properties

摘要

Three types of new lanthanoid(Ln)-containing isopolyoxotungstates [H2N(CH3)(2)](6)Na-6[Ln(4)(H2O)(22)W28O94H2](2)center dot 113H(2)O [Ln = Pr3+ (1), Nd3+ (2), Sm3+ (3)], Na-2[Eu(H2O)(7)](2)[Eu(H2O)(5)](2)[W22O74H2]center dot 20H(2)O (4), and Na3H2[Ln(H2O)(4)] [Ln (H2O)(5)](2)[W22O74H2]center dot 36H(2)O [Ln = Gd3+ (5), Tb3+ (6), Er3+ (7), Tm3+ (8), Yb3+ (9), Lu3+ (10)] have been obtained by reacting Na2WO4 center dot 2H(2)O with Ln(NO3)(3)center dot 6H(2)O in the presence of dimethylamine hydrochloride in the acidic aqueous solution and structurally characterized by elemental analyses, IR spectroscopy, UV spectroscopy, electrospray ionization mass spectrometry (ESI-MS), thermogravimetric (TG) analyses, and single-crystal X-ray diffraction. 1, 2, and 3 are isostructural and display a one-dimensional (1-D) chain-like alignment built by hexameric Ln(8)-comprising [Ln(4)(H2O)(22)W28O94H2](2)(12-) entities via [Ln(H2O)(5)](3+) connectors. The consists of two [Ln(4)(H2O)(22)W28O94H2](6-) subunits connected by two W-O-Ln-O-W linkers. Intriguingly, the rare lambda-shaped octacosatungstate [W28O94H2](18-) moiety observed in the [Ln(4)(H2O)(22)W28O94H2](6-) subunit is composed of two undecatungstate [W11O38H](9-) fragments joined through a hexatungstate [W6O22](8-) fragment by sharing four mu(2)-O atoms. In 4, 22-isopolytungstate [W22O74H2](14-) anions are interlinked together by four W-O-Eu1-O-W linkers giving rise to the 1-D chain motif, and then adjacent 1-D chains are further bridged through multiple W-O-Eu2-O-W connectors to engender the two-dimensional extended sheet structure with the 4-connected topology. The isomorphic 5-10 demonstrate the discrete structure consisting of a [Ln(H2O)(4)][Ln (H2O)(5)](2) [W22O74H2](8-) unit. The pH ranges in which 3, 4, and 9 are stable in aqueous solution have been examined by -virtue of UV and ESI-MS spectra. The solid-state luminescent properties of 3, 4, and 6 have been probed at room temperature. 3 displays the pink emission derived from characteristic emission bands of the Sm3+ cations that correspond to transitions from the (4)G(5/2) excited-state to lower H-6(J) (J = 5/2, 7/2, 9/2, 11/2) levels, 4 emits the red light that mainly results from the D-5(0) -> F-7(2) transition of the Eu3+ cations, and 6 manifests the green luminescence mainly originating from the D-5(4) -> F-7(5) transition of the Tb3+ cations.