A new CuII(4,5-diazafluoren-9-one)-capped Keggin derivative: Hydrothermal synthesis and crystal characterization

A new α-Keggin POM derivative [ Cu 2 I ( DF ) 2 H 2 O ] [ HPMo 10 VI Mo 2 V O 40 { Cu II ( DF ) } ] (1) (DF = 4,5-diazafluoren-9-one) has been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR, XPS spectra, thermogravimetric analysis and cyclic voltammetry. In compound 1, the polyoxoanion cluster [ PMo 10 VI Mo 2 V O 40 ] 5 - is decorated by a single capping {Cu(DF)}2+ subunit via four bridging oxygen atoms on a {Mo4O4} pit. The isolated copper dimer unit { Cu 2 I ( DF ) 2 H 2 O } 2 + acts as counter cation, in which the organic ligand DF exhibits a rare coordination mode. Furthermore, the capped Keggin polyoxoanions [ PMo 10 VI Mo 2 V O 40 { Cu II ( DF ) } ] 3 - are fused together via the copper dimers through the weak Cu ⋯ O interactions to form chains. Hybrid 1 was used as a solid bulk modifier to fabricate a carbon paste electrode (1-CPE) by direct mixing. The electrochemical and electrocatalytic behaviors of the 1-CPE have been studied in detail.