Two sandwich-type compounds from Keggin polyoxometalate, d10 metals and the product of in situ catalyzed decarboxylation of pyrazine-2,3-dicarboxylic acid

Abstract Two supramolecular Keggin polyoxometalate compounds with sandwich-type structure, [Cu 4 (pz) 6 ][SiW 12 O 40 ]∙2H 2 O ( 1 ) and [Ag 2 (pz) 2 ][Ag 2 (pz)(H 2 O) 2 (SiW 12 O 40 )] ( 2 )(pz = pyrazine), have been synthesized by in situ generation of pyrazine ligand from pyrazine-2,3-dicarboxylic acid (H 2 pzdc) under hydrothermal conditions and characterized by IR spectroscopy and TGA. In 1 the combination of Cu I ions and pz creates a honeycomb 2-D layer, these layers sandwich [SiW 12 O 40 ] 4 − anions, constructing a multi-sandwich supramolecular compound. In 2 a 2-D layer is formed from [Ag 2 (pyrazine) 2 ∙(H 2 O) 2 ] n 2n + and [SiW 12 O 40 ] n 4 n − and the layers sandwich 1-D [Ag 2 -(pyrazine) 2 ] n 2n + linear chains to construct another multi-sandwich supramolecular compound. The pyrazine molecules in 1 and 2 are the product of decarboxylation reaction of pyrazine-2,3-dicarboxylic acid catalyzed by Keggin polyoxometalates. Two compounds show the similar intense fluorescent emissions in the solid state.