Tuning the Dimensionality of the Coordination Polymer Based on Polyoxometalate by Changing the Spacer Length of Ligands

Through tuning the spacer length of flexible bis(triazole) ligands, three Keggin anion-based coordination polymers with different dimensionalities, [Cu 4 (H 2 O) 4 (bte) 2 (HPMo VI 10 Mo V 2 O 40 )]·2H 2 O ( 1 ) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane), [Cu(btb)][Cu 2 (btb) 2 (PMo 12 O 40 )] ( 2 ) (btb = 1,4-bis(1,2,4-triazol-1-y1)butane), and [Cu 5 (btx) 4 (PMo VI 10 Mo V 2 O 40 )] ( 3 ) (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane), were synthesized and structurally characterized. Compound 1 exhibits a ladder-like chain, in which the polyoxometalate (POM) anions act as the “middle rails” of the ladder. The bte ligand with shortest spacer length acts as not only the bridging linker but also the chelator, which terminates the dimensional extension. Compound 2 exhibits a 2D POM-based framework, containing POM/Cu/btb grid-like layers. In compound 3, there exist three sets of (12 3 )(12 1 ) 2 2D Cu-btx frameworks to generate a 3-fold interpenetrating structure, into which the hexadentate POM anions are inserted to construct a 3D structure. The structural analyses reveal that the spacer length of flexible bis(triazole) ligands has influence on the dimensionality of these compounds.