Three new copper phosphonate coordination polymers have been obtained following very soft synthetic routes, and their structures were determined ab initio from powder X-ray diffraction data. They are based on the two building blocks α,α′-m-xylylenediphosphonic and α,α′- p-xylylenediphosphonic acid, either exclusively or combined with 4,4′-bipyridine as an ancillary ligand. The compound obtained from α,α′-m-xylylenediphosphonate has the formula Cu(HO 3PCH 2) 2C 6H 4•3H 2O and a 2D structure of mixed organic-inorganic layers built up by the connection of inorganic chains made of edge-sharing copper octahedra via organic bridging groups. The compound obtained from α,α′-m- xylylenediphosphonate and 4,4′-bipyridine as a coligand has the formula Cu[(HO 3PCH 2) 2C 6H 4][N(CH) 4CC(CH) 4N]•2H 2O and a 2D structure based on the connection, via the diphosphonic ligand, of the linear chains resulting from the bridging of copper atoms by the bipyridine moieties. The compound obtained using α,α′-p-xylylenediphosphonate and 4,4′-bipyridine as a coligand has the same formula and a 2D structure closely resembling that of the previous compound. The influence of the factors driving the molecular assembly is discussed, pointing out the crucial role played by the 4,4′-bipyridine in promoting the π-π stacking interactions. With increasing temperatures, the compounds revealed a loss of water molecules bound to copper; in particular, heating the copper α,α′-m-xylylenediphosphonate-bipyridine results in a relatively stable phase with unsaturated coordination sites on the metal atoms. This behavior was confirmed by magnetic susceptibility and electron paramagnetic resonance measurements which also provided evidence for a partial reversibility of the dehydration process and of the occurrence of weak antiferromagnetic interactions between Cu(II) ions. © 2012 American Chemical Society.
Influence of π-π Stacking interactions on the assembly of layered copper phosphonate coordination polymers: Combined powder diffraction and electron paramagnetic resonance study
Taddei M.;
2012-01-01
Abstract
Three new copper phosphonate coordination polymers have been obtained following very soft synthetic routes, and their structures were determined ab initio from powder X-ray diffraction data. They are based on the two building blocks α,α′-m-xylylenediphosphonic and α,α′- p-xylylenediphosphonic acid, either exclusively or combined with 4,4′-bipyridine as an ancillary ligand. The compound obtained from α,α′-m-xylylenediphosphonate has the formula Cu(HO 3PCH 2) 2C 6H 4•3H 2O and a 2D structure of mixed organic-inorganic layers built up by the connection of inorganic chains made of edge-sharing copper octahedra via organic bridging groups. The compound obtained from α,α′-m- xylylenediphosphonate and 4,4′-bipyridine as a coligand has the formula Cu[(HO 3PCH 2) 2C 6H 4][N(CH) 4CC(CH) 4N]•2H 2O and a 2D structure based on the connection, via the diphosphonic ligand, of the linear chains resulting from the bridging of copper atoms by the bipyridine moieties. The compound obtained using α,α′-p-xylylenediphosphonate and 4,4′-bipyridine as a coligand has the same formula and a 2D structure closely resembling that of the previous compound. The influence of the factors driving the molecular assembly is discussed, pointing out the crucial role played by the 4,4′-bipyridine in promoting the π-π stacking interactions. With increasing temperatures, the compounds revealed a loss of water molecules bound to copper; in particular, heating the copper α,α′-m-xylylenediphosphonate-bipyridine results in a relatively stable phase with unsaturated coordination sites on the metal atoms. This behavior was confirmed by magnetic susceptibility and electron paramagnetic resonance measurements which also provided evidence for a partial reversibility of the dehydration process and of the occurrence of weak antiferromagnetic interactions between Cu(II) ions. © 2012 American Chemical Society.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
