**3. Results and Discussion**

#### *3.1. Synthesis Description*

Compounds **1** and **2** are all based on Cd2Ge8V12 and compounds **3** and **4** are based on Ge6V15. The alkalinity (pH > 9) and the stirring time of the reaction mixture are important for the formation of Ge6V15 in compounds **3** and **4**. We have a relatively clear grasp of the synthetic conditions of the two different clusters. The molar ratio of V2O5 to GeO2 for compounds **1** and **2** is about 1:2, and the molar ratios of NH4VO3 to GeO2 for compounds **3** and **4** are 2:1. The addition of 2, 2 -bpy is important for the preparations of compounds **2** and **3**. Though it is absent in the products, 2, 2 -bpy is required for the syntheses of compounds **2** and **3**. It should be noted that such a phenomenon is not unusual in hydrothermal preparations [74].

#### *3.2. Description of Crystal Structures*
