Syntheses, structures and electrochemical properties of lanthanide coordination polymers templated by cobalt-substituted heteropolyanion

Abstract

• Four three-dimensional polyoxometalate-based supramolecules were obtained under hydrothermal conditions. • Regular ribbons formed by lanthanide ions and BPDO ligands are piled up via strong hydrogen bonds. • [CoW 12 O 40 ] 5− polyanions act as templates to hold the charge equilibrium and fill the pores. • The title compounds have electrochemical activities ascribed to the W-centers and exhibit POM-based electrocatalytic behavior for reduction of nitrite. A new series of polyoxometalate-based supramolecules, namely, [Ln(HBPDO) 2 (BPDO) 2.5 (H 2 O) 2 ][CoW 12 O 40 ]· x H 2 O (Ln= Gd for 1h , Pr for 2 , Sm for 3 , Eu for 4 ； x = 3, 2, 2, 2), were obtained under hydrothermal conditions in the presence of 4,4′-bipyridine-N,N′-dioxide (BPDO) as organic ligands and Keggin-anions [CoW 12 O 40 ] 5- as templates. The title compounds are isostructural and constructed by infinite chains [Ln(HBPDO) 2 (BPDO) 2.5 (H 2 O) 2 ] 5+ . Adjacent chains are piled up via strong hydrogen bonds to generate a three-dimensional supramolecular structure. The Keggin-anions [CoW 12 O 40 ] 5- act as templates to hold the charge equilibrium through electrostatic interaction, as well as to fill the pores by strong hydrogen bonds. Moreover, the electrochemical properties have been primarily investigated. The results reveal that the compounds retain the redox capacity of the {CoW 12 } polyoxide anions.