Bismuth 2,6-pyridinedicarboxylates: Assembly of molecular units into coordination polymers, CO2sorption and photoluminescence

Abstract

Six inorganic–organic bismuth 2,6-pyridinedicarboxylate (pdc) compounds, [Bi(2,6-pdc)₃]·3(dma), 1, [Bi(2,6-pdc)₃]·3(dma)·2(H₂O), 2, [Bi(2,6-pdc)₂(dmf)]·(dma), 3, Bi(2,6-pdc)(2,6-pdcme)(MeOH), 4, [LiBi(2,6-pdc)₃(H₂O)]·2(dma), 5, and Li₅Bi(2,6-pdc)₄(H₂O)₂, 6 (where dma = dimethyl ammonium cation, dmf = dimethylformamide and 2,6-pdcme = 6-methyl-oxycarbonyl pyridine 2-carboxylate) have been synthesized under solvothermal conditions and their structures determined by single crystal X-ray diffraction. Compounds 1–4 have molecular structures whereas compounds 5 and 6 form one- and three-dimensional frameworks, respectively. Compounds 1 and 2, both having similar monomeric bismuth coordination units, which are connected non-covalently into a (4,4)-connected square lattice by H-bonding interactions through dma cations. Compounds 3 and 4, both have a similar dimeric bismuth coordination unit. In 3, the dimers are connected into a one-dimensional chain by H-bonding interactions through dma cations. In the partially esterified and neutral 4, there was no such H-bonding interactions due to the absence of any dma cations. Compounds 5 and 6 have a similar monomeric bismuth coordination unit to that seen in 1 and 2. In 5, the monomers are connected through lithium cations into one-dimensional chains, which further interact non-covalently by H-bonding interactions through dma cations. In the lithium-rich 6, the monomers are connected by the lithium cations and 2,6-pdc anions into a three dimensional structure with intramolecular H-bonding interactions involving the water molecules. The non-porous 5 and 6 exhibit a reasonable amount of H₂ and CO₂ sorptions, respectively. Tb³⁺- and Eu³⁺-doped and co-doped 4 and 5 emit characteristic sensitized green/red/yellow-orange luminescence.