Zr 4 -Substituted polyoxometalate dimers decorated by d -tartaric acid/glycolic acid: syntheses, structures and optical/electrochemical properties

In this article, two new tetra-Zr( iv )-substituted sandwich-type Keggin polyoxometalates functionalized by chiral d -tartaric acid and glycolic acid, K 2 H 10 [Zr 4 (H 2 O) 2 (μ-OH)(μ 3 -O) 2 ( d -tartH)(GeW 10 O 37 ) 2 ]·27H 2 O ( 1 , D-tartH 4 = d -tartaric acid) and K 2 H 10 [Zr 4 (H 2 O) 2 (μ 3 -O) 2 (gly) 2 (GeW 10 O 37 ) 2 ]·32H 2 O ( 2 , glyH 2 = glycolic acid), have been synthesized under hydrothermal conditions and characterized by FT-IR spectra, elemental analysis, single-crystal X-ray structure analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), ultraviolet-visible absorption spectroscopy (UV-vis) and cyclic voltammetry (CV). The structure analysis reveals that both 1 and 2 contain a [Zr 4 (H 2 O) 2 (μ 3 -O) 2 (GeW 10 O 37 ) 2 ] cluster. UV-vis spectra indicate that both compounds are a wide-gap semiconductor. In addition, compound 1 is a chiral Zr( iv )-substituted sandwich-type Keggin cluster because the d -tartH ligand is chiral and the Flack divisor of 1 is 0.00, showing non-linear optical properties. The cyclic voltammograms indicate that compounds 1 and 2 have good electrocatalytic activity in the reduction of H 2 O 2 .