Diversity of POM-based Copper Compounds Obtained from the Same Reaction System

The two simple pathways using metallic copper or copper salts were proposed for obtaining hybrid compounds in mild conditions. The variety of Strandberg- and mixed-metal Keggin-based products (NH4)5n{[Cu(en)2][PMo8V4O40]}n*9nH2O (1), (NH4)4n{[Cu(en)(H2O)][P2Mo5O23]}n*3.5nH2O (2), (NH4)7[PMo8V4O40]*17H2O (3) and (NH4)2n{[Cu(en)2][Cu(en)(H2O)][P2Mo5O23]}n*3nH2O (4) were isolated by varying a composition of the reaction system. A rare four-substituted [PMo8V4O40]7- Keggin anion was obtained. The influence of vanadium source (V2O5, NH4VO3 and (NH4)2V6O16) and copper precursor (metal powder vs. its salts) on the nature of resulting products has been studied. The ex situ EPR study revealed formation of VIV and CuII centers in the reaction mixture during Cu0 dissolution. The obtained compounds have been found to possess electrocatalytic activity in the reduction of iodate and nitrite anions whereas carbon paste electrode modified with compound 4 exhibited a linear current response to L-cysteine. Furthemore, the complex 4 demonstrated rapid and almost complete adsorption of a cationic dye.