Synthesis and Characterization of Two Novel Lanthanide Coordination Polymers with an Open Framework Based on an Unprecedented [Ln7(μ3-OH)8]13+ Cluster

Inner transition metal-modulated metal organic frameworks (IT-MOFs) and their derived nanomaterials: a strategic approach towards stupendous photocatalysis

Photocatalysis, as an amenable and effective process, can be adopted for pollution remediation and to alleviate the ongoing energy crisis. In this case, recently, metal organic frameworks (MOFs) have attracted increasing attention in the field of photocatalysis owning to their unique characteristics including large specific surface area, tuneable pore architecture, mouldable framework composition, tuneable band structure, and exceptional photon absorption tendency complimented with superior anti-recombination of excitons. Among the plethora of frameworks, inner transition metal based-MOFs (IT-MOFs) have started to garner significant traction as photocatalysts due to their distinct characteristics compared to conventional transition metal-based frameworks. Typically, IT-MOFs have the tendency to generate high nuclearity clusters and possess abundant Lewis acidic sites, together with mixed valency, which aids in easily converting redox couples, thereby making them a suitable candidate for various photocatalytic reactions. Therefore, in this contribution, we aim to summarise the excellent photocatalytic performance of IT-MOFs and their composites accompanied by a thorough discussion of their topological changes with a variation in the structure of the metal cluster, fabrication routes, morphological features, and physico-chemical properties together with a brief discussion of computational findings. Moreover, we attempt to explore the scientific understanding of the functionalities of IT-MOFs and their composites with detailed mechanistic pathways for in-depth clarity towards photocatalysis. Furthermore, we present a comprehensive analysis of IT-MOFs for various crucial photocatalytic applications such as H₂/O₂ evolution, organic pollutant degradation, organic transformation, and N₂ and CO₂ reduction. In addition, we discuss the measures employed to enhance their performance with some future directions to address the challenges with IT-MOF-based nanomaterials.

A 12-Connected [Y4((μ3-OH)4]8+ Cluster-Based Luminescent Metal-Organic Framework for Selective Turn-on Detection of F- in H2O

Fluoride ion (F-) is one of the most hazardous elements in potable water. Over intake of F- can give rise to dental fluorosis, kidney failure, or DNA damage. As a result, developing affordable, equipment-free and credible approaches for F- detection is an important task. In this work, a new three dimensional rare earth cluster-based metal-organic framework assembled from lanthanide Y(III) ion, and a linear multifunctional ligand 3-nitro-4,4'-biphenyldicarboxylic acid, formulated as {[Y(μ3-OH)]4[Y(μ3-OH)(μ2-H2O)0.25(H2O)0.5]4[μ4-nba]8}n (1), where H2nba = 3-nitro-4,4'-biphenyldicarboxylic acid, has been hydrothermally synthesized and characterized through infrared spectroscopy (IR), elemental and thermal analysis (EA), power X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD) analyses. X-ray diffraction structural analysis revealed that 1 crystallizes in tetragonal system with P4¯21m space group, and features a 3D framework with 1D square 18.07(3)2 Å2 channels running along the [0,0,1] or c-axis direction. The structure of 1 is built up of unusual eight-membered rings formed by two types of {Y4O4} clusters connected to each other via 12 μ4-nba2- and 4 μ3-OH- ligands. Three crystallographic independent Y3+ ions display two coordinated configurations with a seven-coordinated distorted monocapped trigonal-prism (YO7) and an eight-coordinated approximately bicapped trigonal-prism (YO8). 1 is further stabilized through O-H⋯O, O-H⋯N, C-H⋯O, and π⋯π interactions. Topologically, MOF 1 can be simplified as a 12-connected 2-nodal Au4Ho topology with a Schläfli symbol {420·628·818}{43}4 or a 6-connected uninodal pcu topology with a Schläfli symbol {412·63}. The fluorescent sensing application of 1 was investigated to cations and anions in H2O. 1 exhibits good luminescence probing turn-on recognition ability toward F- and with a limit detection concentration of F- down to 14.2 μM in aqueous solution (Kec = 11403 M-1, R2 = 0.99289, σ = 0.0539). The findings here provide a feasible detection platform of LnMOFs for highly sensitive discrimination of F- in aqueous media.

Three metal complexes with a pyridyl Schiff base: cytotoxicity, migration and mechanism of apoptosis

Three metal complexes [CuL(NO₃)]_n (1), [Cd(HL)(NO₃)₂]_n (2) and [EuL(HCOOH)(H₂O)(NO₃)₂] (3) were synthesized with a pyridyl Schiff ligand L (N'-[(1E)-pyridin-2-ylmethylidene]pyridine-4-carbohydrazide). A crystallographic study revealed that complexes 1 and 2 have a chain structure, and complex 3 is a zero-dimensional monomer. In vitro cytotoxicity studies showed that complex 2 had the best antiproliferative activity against SMMC-7721 cells and complex 3 had the best antiproliferative activity against MDA-MB-231 cells with single-digit IC₅₀ values, both exceeding those of the control drug cisplatin by far. The cell invasion and migration ability through the transwell assay and wound-healing assay showed that the selected complexes could inhibit the invasion and migration of cancer cells. The Hoechst staining assay and ROS generation assay with SMMC-7721 cells indicated that the cytotoxic effects of complex 2 involved apoptosis induction through ROS accumulation. The apoptosis-inducing and cell cycle arrest effects of complex 2 on SMMC-7721 cells indicated that the antitumor effect was achieved through apoptosis induction and inhibition of DNA synthesis by blocking the G₀/G₁ phase of the cell cycle. In addition, complex 2 showed significant inhibition against B. dysentery with an inhibition circle diameter of 24 mm.

Rare-earth metal–organic frameworks: from structure to applications

In the past 30 years, rare-earth metal–organic frameworks (MOFs) have been gaining attention owing to their diverse chemical structures, and tunable properties.

Phosphonate-assisted tetranuclear lanthanide assemblies: observation of the toroidic ground state in the TbIII analogue

The reaction of LnCl3·6H2O with a multidentate flexible Schiff base ligand (LH4), H2O3PtBu and trifluoroacetic acid (tfaH) afforded a series of homometallic tetranuclear complexes, [Ln4(LH2)2(O3PtBu)2(μ2-η1η1tfa)2][2Cl] (Ln = DyIII (1), TbIII (2) and GdIII (3)). The tetranuclear lanthanide core contains two structurally different lanthanide centres, one being in a distorted trigonal dodecahedron geometry and the other in a distorted trigonal prism. Complexes 1-3 were investigated via direct and alternating current (DC and AC) magnetic susceptibility measurements. Only 1 revealed a weak single-molecule magnet (SMM) behaviour. Alternating current (ac) magnetic susceptibility measurements on 1 reveal a frequency-dependent out-of-phase signal. However, the absence of distinct maxima in the χ'' peak (within the temperature/frequency range of our experiments) prevented deduction of the experimental energy barrier for magnetization reversal (Ueff) and the relaxation time. We have carried out extensive ab initio (CASSCF + RASSI-SO + SINGLE_ANISO + POLY_ANISO) calculations on complexes 1-2 to gain deeper insights into the nature of magnetic anisotropy. Our calculations yielded only one exchange coupling parameter between the two LnIII centres bridged by the ligand (neglecting the exchange between the LnIII centres that are not proximal wrt each other). All the extracted J values indicate a weakly antiferromagnetic coupling between the metal centres (J = -0.025 cm-1 for 1 and J = -0.015 cm-1 for 2). Calculated exchange coupled Ucal values of ∼5 and ∼1 cm-1 in 1 and 2 respectively nicely corroborated the experimental observations regarding weak and no SMM characteristics. Our calculations indicated the presence of a net single-molecule toroidal (SMT) behaviour in complex 2. On the other hand, fitting the magnetic data (susceptibility and magnetization) in the isotropic cluster 3 revealed weak AFM exchange couplings of J1 = 0.025 cm-1 and J2 = -0.020 cm-1 which are consistent with those for GdIII ions.

Antibacterial and aqueous dual-responsive sensing activities of monomeric complexes with uncoordinated imidazole sites

The butterfly-shaped monomeric complex is stable and slight soluble in water, which shows antibacterial and aqueous dual-responsive sensing activities.

Halogen dependent symmetry change in two series of wheel cluster organic frameworks built from La18 tertiary building units

Two series of wheel cluster organic frameworks (WCOFs) built from La18 tertiary building units are hydrothermally made, which show halogen-dependent structural symmetry, and demonstrate different chiral performances.

Magnetized property effect of a non-aqueous solvent upon complex formation between kryptofix 22DD with lanthanum(iii) cation: experimental aspects and molecular dynamics simulation

The variation of molar conductance versus mole ratio for (kryptofix 22DD·La)³⁺ complex in methanol solution at different temperatures is in accordance with the variation of pair correlation function of oxygen atoms.

Two Novel Sm and La Metal-Organic Frameworks Suggesting the Reductive Coupling of Carbon Dioxide (CO2) to Oxalate (C2O42-): {[Ln(HPIDC)•(μ4-C2O4)0.5·H2O]·2H2O}n.(Ln=Sm or La)

Complexes formulated as {[Ln(HPIDC)(μ4-C2O4)0.5(H2O)]·2H2O}n [Ln=Sm or La; H3PIDC=2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid] have been synthesised under hydrothermal conditions. The complexes are both built up from T-shaped 3-connected HPIDC2- and 4-connected metal nodes and contain bridging oxalate (C2O42-) ligands, which might have been formed by the reductive coupling of CO2 molecules released from the HPIDC2- ligands through C-C bond cleavage.

Pentanuclear [2.2] spirocyclic lanthanide(iii) complexes: slow magnetic relaxation of the DyIII analogue

A series of [2.2] spirocyclic complexes [Ln₅(LH)₄(η¹-Piv)(η²-Piv)₃(μ₂–η² η¹Piv)₂(H₂O)]·Cl (Ln = Dy^III, Tb^III and Ho^III) were synthesized. Magnetic analysis reveals that the Dy^III analogue showed slow relaxation of magnetization.

Functionalities and architectures of coordination polymers with multi-dimensionalities via transition metal–dicarboxylate ligands

Five coordination polymers based on the flexible H₂dpd ligand and different metal salts have been synthesised. The configuration of the ligand and the reaction temperature have important effects on the final structures.

Two luminescent metal–organic frameworks with multifunctional properties for nitroaromatic compounds sensing and photocatalysis

Two luminescent MOFs were employed as multifunctional materials for selectively sensing of nitroaromatic compounds and photodegradation of RhB.

A twofold interpenetrating three-dimensional zinc-organic framework built from naphthalene-1,4-dicarboxylate and 4,4'-bipyridine ligands

A novel three-dimensional Zn(II) complex, poly[[(μ2-4,4'-bipyridine)(μ4-naphthalene-1,4-dicarboxylato)(μ2-naphthalene-1,4-dicarboxylato)dizinc(II)] dimethylformamide monosolvate monohydrate], {[Zn2(C12H6O4)2(C10H8N2)]·2C3H7NO·H2O)}n, has been prepared by the solvothermal assembly of Zn(NO3)·6H2O, naphthalene-1,4-dicarboxylic acid and 4,4'-bipyridine. The two crystallographically independent Zn atoms adopt the same four-coordinated tetrahedral geometry (ZnO3N) by bonding to three O atoms from three different naphthalene-1,4-dicarboxylate (1,4-ndc) ligands and one N atom from a 4,4'-bipyridine (bpy) ligand. The supramolecular secondary building unit (SBU) is a distorted paddle-wheel-like {Zn2(COO)2N2O2} unit and these units are linked by 1,4-ndc ligands within the layer to form a two-dimensional net parallel to the ab plane, which is further connected by bpy ligands to form the three-dimensional framework. The single net leaves voids that are filled by mutual interpenetration of an independent equivalent framework in a twofold interpenetrating architecture. The title compound is stable up to 673 K. Excitation and luminescence data observed at room temperature show that it emits bright-blue fluorescence.

Ln–Cd heterometal organic–inorganic hybrid materials based on diverse Ln–Cd oxo-cluster chains: syntheses, structures and visible luminescence

Two types of luminescent Ln–Cd heterometal complexes, I and II, based on diverse Ln–Cd oxo-clusters have been synthesized and characterized.