Two Members of the {X 4 Nb 16 O 56 } Family (X = Ge, Si) Based on [(GeOH) 2 Ge 2 Nb 16 H 2 O 54 ] 12– and [K(GeOH) 2 Ge 2 Nb 16 H 3 O 54 ] 10–

Two new heteropolyniobate compounds, (C 2 N 2 H 10 ) 6 [(GeOH) 2 Ge 2 Nb 16 H 2 O 54 ] · 25H 2 O ( 1 ) and [Cu(en) 2 (H 2 O) 2 ] 5 K 10 [K(GeOH) 2 Ge 2 Nb 16 H 3 O 54 ] 2 · 38H 2 O ( 2 , en = ethylenediamine), have been prepared under hydrothermal–conventional combination conditions and structurally characterized by elemental analysis, IR spectroscopy, powder and single‐crystal XRD, diffuse reflection spectroscopy, and thermogravimetric (TG) analysis. Compounds 1 and 2 are based on [(GeOH) 2 Ge 2 Nb 16 H 2 O 54 ] 12– and [K(GeOH) 2 Ge 2 Nb 16 H 3 O 54 ] 10– building blocks, respectively. Compound 1 represents the initially isolated Nb/Ge lacunary derivative and compound 2 exhibits 1D ladderlike chains. The photoluminescence properties and electrochemical properties of compounds 1 and 2 have been investigated.