The synthesis and characterisation of coordination and hydrogen-bonded networks based on 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid

The synthesis, structural and thermal characterisation of a number of coordination complexes featuring the N,O-heteroditopic ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, HL are reported. The reaction of H2L with cobalt(II) and nickel(II) nitrates at room temperature in basic DMF/H2O solution gave discrete mononuclear coordination complexes with the general formula {[M(HL)2(H2O)4]·2DMF} (M = Co (1), Ni (2)), whereas the reaction with zinc(II) nitrate gave [Zn(HL)2]∞, 3, a coordination polymer with distorted diamondoid topology and fourfold interpenetration. Coordination about the tetrahedral Zn(II) nodes in 3 are furnished by two pyrazolyl nitrogen atoms and two carboxylate oxygen atoms to give a mixed N2O2 donor set. Isotopological coordination polymers of zinc(II), {[Zn(HL)2]·2CH3OH·H2O}∞, 4, and cobalt(II), [Co(HL)2]∞, 5, are formed when the reactions are carried out under solvothermal conditions in methanol (80 °C) and water (180 °C), respectively. The reaction of H2L with cadmium(II) nitrate at room temperature in methanol gives {[Cd(HL)2(MeOH)2]·1.8MeOH}∞6, a 2-D (4,4)-connected coordination polymer, whereas with copper(II) the formation of green crystals that transform into purple crystals is observed. The metastable green phase [Cu3(HL)4(μ2-SO4)(H2O)3]∞, 7, crystallises with conserved binding domains of the heteroditopic ligand and contains two different metal nodes: a dicopper carboxylate paddle wheel motif, and, a dicopper unit bridged by sulfate ions and coordinated by ligand pyrazolyl nitrogen atoms. The resultant purple phase {[Cu(HL)2]·4CH3OH·H2O}∞, 8, however, has single copper ion nodes coordinated by mixed N2O2 donor sets with trans-square planar geometry and is threefold interpenetrated. The desolvation of 8 was followed by powder X-ray diffraction and single crystal X-ray diffraction which show desolvation induces the transition to a more closely packed structure while the coordination geometry about the copper ions and the network topology is retained. Powder X-ray diffraction and microanalysis were used to characterise the bulk purity of the coordination materials 1-6 and 8. The thermal characteristics of 1-2, 4-6 and 8 were studied by TG-DTA. This led to the curious observation of small exothermic events in networks 4, 6, and 8 that appear to be linked to their decomposition. In addition, the solid state structures of H2L and that of its protonated salt, H2L·HNO3, were also determined and revealed that H2L forms a 2-D hydrogen bonded polymer incorporating helical chains formed through N-HO and O-HN interactions, and that [H3L]NO3 forms a 1-D hydrogen-bonded polymer

Hypervalent organoiodine(v) metal-organic frameworks: Syntheses, thermal studies and stoichiometric oxidants

This journal is © The Royal Society of Chemistry. Iodinated analogues of the highly porous IRMOF-9 and UiO-67 frameworks were prepared and post-synthetically oxidised with dimethyldioxirane (DMDO). Analysis by X-ray photoelectron spectroscopy (XPS) confirmed promotion to the iodine(v) state and detailed differential scanning calorimetry-thermal gravimetric analysis (DSC-TGA) showed the hypervalent metal-organic frameworks (MOFs) undergo exothermic elimination at ∼200 °C with XPS showing hypervalency is maintained. The hypervalent MOFs are active heterogeneous reagents in sulfoxidation and alcohol oxidation reactions. The crystallinity and porosity of the MOFs were maintained following post-synthetic oxidation, thermolysis and after the heterogeneous reactions, as shown by powder X-ray diffraction (PXRD) and gas adsorption analyses. This work showcases the unique ability MOFs hold for studying chemical reactions and the potential for hypervalent organoiodine MOFs as reuseable oxidants

Interpenetration isomers in isoreticular amine-tagged zinc MOFs

2019 The Royal Society of Chemistry. The effect of increasing steric size of pendant amine substituents on structural isoreticulation has been studied systematically in a series of Zn-MOFs. Linear biphenyl dicarboxylic acids tagged with pendant primary amine (H2bpdc-NH2), allylamine (H2bpdc-NHallyl), diallylamine (H2bpdc-N(allyl)2) and dimethylamine (H2bpdc-NMe2) groups react with zinc nitrate in DMF to yield a set of interpenetrated MOFs, WUF-11-14, respectively, that are structurally akin to IRMOF-9. The allylated amine ligands undergo C-N cleavage reactions under the synthesis conditions, yielding WUF-12 and WUF-13 as multivariate MOFs. The single crystal X-ray crystallography on this set of MOFs was not straightforward and we give a salutary account of the difficulties encountered. Gas adsorption measurements combined with surface area calculations provide invaluable support for the crystallographic assignments. The crystallographic analyses reveal subtle differences in the relative positions of the interpenetrating frameworks, and we present a classification system for this type of MOF and analyse related examples available in the literature. CO2 adsorption measurements revealed that WUF-14, which features the strongest Brønsted basic dimethylamine tag group, has the highest capacity, isosteric heat of adsorption, and CO2/N2 selectivity

The synthesis and characterisation of coordination and hydrogen-bonded networks based on 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid

The synthesis, structural and thermal characterisation of a number of coordination complexes featuring the N,O-heteroditopic ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, HL are reported. The reaction of H2L with cobalt(II) and nickel(II) nitrates at room temperature in basic DMF/H2O solution gave discrete mononuclear coordination complexes with the general formula {[M(HL2(H2O)4]·2DMF} (M = Co (1), Ni (2)), whereas the reaction with zinc(ii) nitrate gave [Zn(HL)2]∞, 3, a coordination polymer with distorted diamondoid topology and fourfold interpenetration. Coordination about the tetrahedral Zn(II) nodes in 3 are furnished by two pyrazolyl nitrogen atoms and two carboxylate oxygen atoms to give a mixed N2O2 donor set. Isotopological coordination polymers of zinc(II), {[Zn(HL)2]·2CH3OH·H2O}∞, 4, and cobalt(II), [Co(HL)2]∞, 5, are formed when the reactions are carried out under solvothermal conditions in methanol (80°C) and water (180°C), respectively. The reaction of H2L with cadmium(II) nitrate at room temperature in methanol gives {[Cd(HL)2(MeOH)2]·1.8MeOH}∞6, a 2-D (4,4)-connected coordination polymer, whereas with copper(II) the formation of green crystals that transform into purple crystals is observed. The metastable green phase [Cu3HL)4(μ2-SO4)(H2O3]∞, 7, crystallises with conserved binding domains of the heteroditopic ligand and contains two different metal nodes: a dicopper carboxylate paddle wheel motif, and, a dicopper unit bridged by sulfate ions and coordinated by ligand pyrazolyl nitrogen atoms. The resultant purple phase {[Cu(HL)2]·4CH3OH·H2O}∞, 8, however, has single copper ion nodes coordinated by mixed N2O2 donor sets with trans-square planar geometry and is threefold interpenetrated. The desolvation of 8 was followed by powder X-ray diffraction and single crystal X-ray diffraction which show desolvation induces the transition to a more closely packed structure while the coordination geometry about the copper ions and the network topology is retained. Powder X-ray diffraction and microanalysis were used to characterise the bulk purity of the coordination materials 1-6 and 8. The thermal characteristics of 1-2, 4-6 and 8 were studied by TG-DTA. This led to the curious observation of small exothermic events in networks 4, 6, and 8 that appear to be linked to their decomposition. In addition, the solid state structures of H2L and that of its protonated salt, H2L·HNO3, were also determined and revealed that H2L forms a 2-D hydrogen bonded polymer incorporating helical chains formed through N-H⋯O and O-H⋯N interactions, and that [H3L]NO3 forms a 1-D hydrogen-bonded polymer.</p

Mixed-Component Sulfone–Sulfoxide Tagged Zinc IRMOFs: In Situ Ligand Oxidation, Carbon Dioxide, and Water Sorption Studies

Reported here are the syntheses and adsorption properties of a series of single- and mixed-component zinc IRMOFs derived from controlled ratios of sulfide and sulfone functionalized linear biphenyldicarboxylate (bpdc) ligands. During MOF synthesis the sulfide moieties undergo in situ oxidation, giving rise to sulfoxide functionalized ligands, which are incorporated to give mixed-component sulfoxide-sulfone functionalized MOFs. The single- and mixed-component systems all share the IRMOF-9 structure type as determined by a combination of single crystal and powder X-ray diffraction analyses. The functionalized IRMOF-9 series was investigated by N2, CO2, and water adsorption measurements. MOFs containing higher proportions of sulfoxide have slightly larger accessible surface areas and pore volumes, whereas MOFs containing a greater proportion of the sulfone functionality demonstrated higher CO2 adsorption capacities, enthalpies of CO2 adsorption, and CO2/N2 selectivities. Water adsorption studies at 298 K showed the MOFs to have pore-filling steps starting around 0.4 P/P0. In general, only small changes in water adsorption were observed with regards to ligand ratios in the mixed-component MOFs, suggesting that the location of the step is primarily determined by the pore size. A ligand-directed fine-tuning approach of changing alkyl chain length was demonstrated to give smaller more hydrophobic pores with better adsorption characteristics