Synthesis and characterisation of metal–organic frameworks containing bis(β-diketonate) linkers

Abstract

Four metal–organic frameworks have been isolated and structurally characterised from the reaction between Zn(NO3)2·6H2O and the bis(β-diketone) 3,4-diacetyl-2,5-dioxohexane in the presence of triethylamine. When the reaction was carried out in DMF/chloroform or DMSO/methanol the one-dimensional coordination polymers {[Zn(L)(DMF)]·0.65CHCl3·0.35DMF}∞1 and {[Zn3(L)3(MeOH)(DMSO)4.2]·0.8DMSO}∞2, respectively, were isolated in low yield. When the reaction was carried out in methanol, three products were isolated – {[Zn2(L)2(MeOH)2]·2MeOH}∞3, {[Zn2(L)2(MeOH)]·2H2O}∞4 and {[Zn2(L)2(OH2)2]}∞5. Compounds 3 and 4 have structures in which Zn2(μ-β-diketonate)2(β-diketonate)2 dimers are interlinked into similar two-dimensional networks. Analyses suggest 5 has a similar structure, though with terminal aqua ligands instead of methanol ligands. The reaction between Cd(NO3)2·4H2O, 3,4-diacetyl-2,5-dioxohexane and triethylamine in methanol gave {[Cd2(L)2(H2O)2]·2.5H2O}∞6, which has a similar network structure to 3 and 4. These compounds are the first structurally characterised network structures based on bis(β-diketonate) ligands, and they demonstrate that these ligands can behave in an analogous manner to dicarboxylates.