First lanthanide coordination polymers with N,N-dimethylformamide hydrolysis induced formate ligands

Crystal structure and Hirshfeld surface analysis of a new mononuclear copper(II) complex: [bis-(pyridin-2-yl-κN)amine](formato-κO)(m-hy-droxy-benzoato-κ2O,O')copper(II)

A new mononuclear copper(II) complex, [Cu(C7H5O3)(HCO2)(C10H9N3)], containing mixed N- and O-donor ligands, 2,2'-di-pyridyl-amine (dpyam) and m-hy-droxy-benzoate (m-OHbenz), has been obtained from a solvent mixture. The coordination environment of the CuII ion is distorted square-pyramidal with a [N2O3] coordination set originating from the chelating dpyam and m-OHbenz ligands in the basal plane and the O atom of a formato ligand at the apical position. The crystal structure of the title complex is stabilized by N-H⋯O, O-H⋯O, C-H⋯O hydrogen-bonding, π-π and C-H⋯π inter-molecular inter-actions, which were qu-anti-fied by Hirshfeld surface analysis.

An Interesting Conversion Route of Mononuclear Zinc Complex to Zinc Mixed Carboxylate Coordination Polymer

A complex [Zn(bpy)(acr)₂]·H₂O (1) was converted in a DMF medium (DMF = N,N'-dimethylformamide) into a coordination polymer [Zn(bpy)(acr)(HCOO)]_n (1a) (bpy = 2,2'-bipyridine, and Hacr = acrylic acid), and the species was fully characterized through a single crystal X-ray diffraction. Additional data were obtained by IR and thermogravimetric analysis. Complex (1a) crystalized the coordination polymer in the space group Pca2₁ of an orthorhombic system. Structural characterization revealed that Zn(II) adopted a square pyramidal stereochemistry generated by bpy molecules, coordinated by chelate, acrylate, and formate ions as unidentate and bridged, respectively. The presence of both the formate and the acrylate with different coordination modes generated two bands in ranges that were characteristic for the carboxylate vibration modes. Thermal decomposition occurs in two complex steps: it first happens via a bpy release, which is followed by an overlapped process that is associated with acrylate and formate decomposition. The obtained complex is of present interest due to the presence of two different carboxylates in its composition and situation, which is rarely reported in the literature.

Metal-Organic Framework vs. Coordination Polymer—Influence of the Lanthanide on the Nature of the Heteroleptic Anilate/Terephtalate 3D Network

Metal-organic frameworks (MOFs), whose definition has been regularly debated, are a sub-class of coordination polymers (CPs) which may feature both an overall 3D architecture and some degree of porosity. In this context, MOFs based on lanthanides (Ln-MOFs) could find many applications due to the combination of sorption properties and magnetic/luminescent behaviors. Here we report rare examples of 3D Ln-CPs based on anilate linkers, obtained under solvothermal conditions using a heteroleptic strategy. The three compounds of formula [Yb2(μ-ClCNAn)2(μ-F4BDC)(H2O)4]·(H2O)3 (1), [Er2(μ-ClCNAn)2(μ-F4BDC)(H2O)4]·(H2O)4 (2) and [Eu2(μ-ClCNAn)2(μ-F4BDC)(H2O)6] (3) have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and optical measurements. Structural characterization revealed that compounds 1 and 2 present an interesting MOF architecture with extended rectangular cavities which are only filled with water molecules. On the other hand, compound 3 shows a much more complex topology with no apparent cavities. We discuss here the origins of such differences and highlight the crucial role of the Ln(III) ion nature for the topology of the CP. Compounds 1 and 2 now offer a playground to investigate the possible synergy between gas/solvent sorption and magnetic/luminescent properties of Ln-MOFs.

2D and 3D metal-organic frameworks constructed with a mechanically rigidified [3]rotaxane ligand

A mechanically interlocked [3]rotaxane was newly designed, synthesized, and employed as a ligand for constructing metal-organic frameworks (MOFs). The nano-confinement by macrocycles forces the soft bis-isophthalate axle into a pseudo-rigid conformation and coordinates to zinc(II) ions, affording a two- or three-dimensional MOF under controlled conditions. The 2D MOF exhibits a neutral framework with a periodic puckering sheet structure, while an anionic framework with a pts topology was observed for the 3D MOF. The phase purity of both bulk materials was confirmed by powder X-ray diffraction. Thermogravimetric analysis reveals that both materials are stable up to 250 °C. The success of applying mechanical bonds to rigidify flexible ligands provides new insights for the design of metal-organic frameworks.

Failure-Experiment-Supported Optimization of Poorly Reproducible Synthetic Conditions for Novel Lanthanide Metal-Organic Frameworks with Two-Dimensional Secondary Building Units*

Novel metal-organic frameworks containing lanthanide double-layer-based secondary building units (KGF-3) were synthesized by using machine learning (ML). Isolating pure KGF-3 was challenging, and the synthesis was not reproducible because impurity phases were frequently obtained under the same synthetic conditions. Thus, dominant factors for the synthesis of KGF-3 were identified, and its synthetic conditions were optimized by using two ML techniques. Cluster analysis was used to classify the obtained powder X-ray diffractometry patterns of the products and thus automatically determine whether the experiments were successful. Decision-tree analysis was used to visualize the experimental results, after extracting factors that mainly affected the synthetic reproducibility. Water-adsorption isotherms revealed that KGF-3 possesses unique hydrophilic pores. Impedance measurements demonstrated good proton conductivities (σ=5.2×10^-4  S cm^-1 for KGF-3(Y)) at a high temperature (363 K) and relative humidity of 95 % RH.

Ion-exchange resin as a new tool for characterisation of coordination compounds and MOFs by NMR spectroscopy

¹H and ¹³C NMR spectroscopy is used to investigate the organic constituents of paramagnetic MOFs and coordination compounds using a cationic exchange resin. Post-modifications on MOFs were performed and quantitatively determined by this methodology.

A series of 3D lanthanide coordination polymers decorated with a rigid 3,5-pyridinedicarboxylic acid linker: syntheses, structural diversity, DFT study, Hirshfeld surface analysis, luminescence and magnetic properties

Single crystal X-ray diffraction studies reveal the formation of six new coordination polymers (CPs) with the general formulas [Dy(3,5-pdc)(3,5-pdcH)(H2O)2]n·nH2O (1), [Pr2(3,5-pdc)3(H2O)2]n·2n(H2O) (2), [Sm2(3,5-pdc)3(H2O)3]n·nH2O (3), {[Eu2(3,5-pdc)3(H2O)3(CH3CHO)]n·n[2(H2O)(DMF)]} (4), {[Gd2(3,5-pdc)3 (H2O)2]n·2nH2O} (5) and [Er(3,5-pdc)(adip)0.5(H2O)]n (6) (where 3,5-pdc2- = fully deprotonated; 3,5-pdcH- = partially deprotonated 3,5-pyridinedicarboxylic acid; adip2- = fully deprotonated adipic acid; and DMF = dimethylformamide) by solvothermal self-assembly of lanthanide ions with rigid 3,5-pyridinedicarboxylic acid as a linker and adipic acid as an auxiliary flexible spacer (only coordinated in CP 6). CPs 1 and 2 crystallize in the triclinic P1[combining macron] space group, whereas CPs 3, 4 and 6 crystallize in the monoclinic P21/n, P21/c and C2/c space groups, respectively. CP 5 exhibits the trigonal R3 space group. The 3,5-pdc ligand exhibits eight diverse coordination modes in CPs 1-6, whereas the adipic acid spacer in CP 6 shows only one coordination mode (μ4-κO:κO,O:κO:κO,O). The organic ligands interconnect with metal ions to generate 3D metal-organic frameworks with a variety of intriguing topologies. Theoretical studies, DFT calculations and Hirshfeld surface analysis support the structures adopted by the various CPs. CPs 3 (Sm) and 4 (Eu) emit strong ligand-sensitized characteristic f-f luminescence. Weak ferromagnetic interactions have been studied at low temperatures for CP 1 and CP 5.

A new ZnII coordination polymer based on 4-(pyridin-4-yl)benzoic and formic acids: in-situ synthesis, crystal structure and luminescence properties

The title compound, poly[(μ2-formato-κ3 O,O′:O)[μ2-4-(pyridin-4-yl)benzoato-κ3 N:O,O′]zinc(II)], [Zn(C12H8NO2)(HCOO)] n , has been synthesized in situ and characterized by thermogravimetric analysis (TGA) and single-crystal and powder X-ray diffraction analyses. The polymer contains two independent structural units in the asymmetric unit. These are constructed from Zn2+ ions, 4-(pyridin-4-yl)benzoate (4-pbc) bridges and in-situ-generated formate ligands, forming two similar two-dimensional (2D) layer structures. These similar 2D layers are arranged alternately and are linked with each other by dense C—H...O hydrogen bonds to generate a three-dimensional (3D) supramolecular framework. The crystal is pseudomerohedrally twinned about [201]. Compared with free 4-Hpbc, the polymer exhibits a red shift and significantly enhanced solid-state luminescence properties.

A cuboidal [Ni4O4] cluster as a precursor for recyclable, carbon-supported nickel nanoparticle reduction catalysts

A pyridine alkoxide ligated cuboidal [Ni₄O₄] cluster has been selected as the precursor to synthesize carbon-hosted Ni nanoparticles for catalytic conversion of 4-nitrophenol to 4-aminophenol.

A series of lanthanide–organic frameworks possessing arrays of 2D intersecting channels within a 3D pillar-supported packed double-decker network and Co2+-induced luminescence modulation

Intersecting channels are observed in the 3D network ofFJU6.