3.2.1. Synthesis of Na4{V5Mo2O19[CH3C(CH2O)3]}·13H2O (1)

Na2MoO4·2H2O (0.88 g, 2.00 mmol) and V2O5 (0.45 g, 2.50 mmol) were mixed in 10 mL of deionized water, and then CH3C(CH2OH)3 (0.24 g, 2.00 mmol) was added under stirring. Concentrated HCl was used to adjust the pH of the mixture to 4~5, which was further heated to 60 ◦C and maintained for 4 h. After a hot filtration process, a light brown solution was obtained, which generated light brown crystals after about one week at room temperature with a yield of 54.1% based on Mo. Elemental analysis calcd. (%) for Na4{V5Mo2O19[CH3C(CH2O)3]}·13H2O (Mw = 1193.87 g mol<sup>−</sup>1): C 5.03%, H 2.96%, Na 7.70%, V 21.33%, and Mo 16.07%; found C 5.06%, H 2.98%, Na 7.71%, V 21.50%, and Mo 16.01%.


**Table 2.** The summary of crystal data and structural refinements for compounds **1** and **2**.

*<sup>a</sup> R*<sup>1</sup> = Σ||Fo| − |Fc||/Σ|Fo|. *<sup>b</sup> wR*<sup>2</sup> = Σ[*w*(Fo <sup>2</sup> − Fc 2) 2]/Σ[*w*(Fo 2) 2] 1/2.
