Synthesis, structural characterization and properties of a series of heteropolyoxomolybdates: AlMo 6 (OH) 6 O 18 3− , GeMo 12 O 40 4− , GeMo 6 O 22 (Hmal) 3 7− , SiMo 12 O 40 4− , and TeMo 6 O 24 6− | Synapse