Two Anderson-type polyoxometalate-induced various Co-complexes based on a rigid pyrazine-bis(triazole) ligand

Abstract Two new Anderson-type polyoxometalate (POM)-based metal-organic complexes {Co 2 (H 2 pytty) 2 [CrMo 6 (OH) 5 O 19 ](H 2 O) 8 }·10H 2 O ( 1 ), {Co 5 (pytty) 2 [TeMo 6 O 24 ](H 2 O) 16 }·6H 2 O ( 2 ) (H 2 pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl) have been synthesized under hydrothermal condition and characterized by IR spectra, elemental analyses, single crystal X-ray diffraction, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). Complex 1 is a 0D structure containing a cation [Co 2 (H 2 pytty) 2 ] 4+ and an isolated B-type [CrMo 6 (OH) 5 O 19 ] 4− anion. When A-type [TeMo 6 O 24 ] 6− was used, complex 2 shows a 2D layer with two kinds of 1D chains. No report on the combination of pyrazine-bis(triazole) and Anderson-type POM was found up to now. The electrochemical behaviour and electrocatalytic activities of two title complexes have been systemically studied and discussed. In addition, the redox potentials of complexes 1 and 2 are highly sensitive of pH and may be used as a kind of potential pH sensor.