Luminescent lanthanide mixed N-phthaloylglycinate and terephthalate coordination polymers: Structural and optical properties.

A new class of lanthanide mixed-carboxylate ligands compounds with formula {[Ln2 (phthgly)4 (bdc)(H2 O)6 ]·(H2 O)4 }∞ , labelled as Ln3+ : Eu (1) and Gd (2) coordination polymers (CP) were synthesized under mild reaction conditions between lanthanide nitrate salts and a solution of N-phthaloylglycine (phthgly) and terephthalic (bdc) ligands. The (1) and (2) coordination polymers were formed by symmetric binuclear units, in which phthgly and bdc carboxylate ligands are coordinated to the lanthanide ions by different coordination modes. Surprisingly, all organic ligands participate in hydrogen bonding interactions, forming an extremally rigid crystalline structure. The red narrow emission bands from the 5 D0 →7 FJ transitions of the Eu3+ ion show a high colour purity. The intramolecular energy transfer process from L→Eu3+ ion has been discussed. The experimental intensity parameters (Ω2,4 ) reflect lower angular distortion and polarizability of the chemical environment around the metal ion compared with other Eu3+ compounds reported in the literature. This novel class of coordination polymer offers a more attractive platform for developing luminescent functional materials for different applications.

The Methylene Spacer Matters: The Structural and Luminescent Effects of Positional Isomerism of n-Methylpyridyltriazole Carboxylate Semi-Rigid Ligands in the Structure of Zn(II) Based Coordination Polymers.

Two Zn(II) coordination polymers (CPs) based on n-methylpyridyltriazole carboxylate semi-rigid organic ligands (n-MPTC), with n = 3 (L1) and 4 (L2), have been prepared at the water n-butanol interphase by reacting Zn(NO3)2·4H2O with NaL1 and NaL2. This allows us to systematically investigate the influence of the isomeric positional effect on their structures. The organic ligands were obtained by saponification from their respective ester precursors ethyl-5-methyl-1-(pyridin-3-ylmethyl)-1H-1,2,3-triazole-4-carboxylate (P1) and ethyl-5-methyl-1-(pyridin-4-ylmethyl)-1H-1,2,3-triazole-4-carboxylate (P2), resulting in their corresponding sodium salt forms, 3-MPTC, and 4-MPTC. The structure of the Zn(II) CPs determined by single-crystal X-ray diffraction reveals that both CPs have 2D supramolecular hydrogen bond networks. The 2D supramolecular network of [Zn(L1)]n (1) is built up by hydrogen bond interactions between oxygen and hydrogen atoms between neighboring n-methylpyridyltriazole molecules, whereas in [Zn(L2)·4H2O]n (2) the water molecules link 1D polymeric chains forming a 2D supramolecular aggregate. The structures of 1 and 2 clearly show that the isomeric effect in the semi-rigid ligands plays a vital role in constructing the Zn(II) coordination polymers, helped by the presence of the methylene spacer group, in the final structural conformation. The structures of 1 and 2 significantly affect their luminescent properties. Thus, while 2 shows strong emission at room temperature centered at 367 nm, the emission of 1 is quenched substantially.

Very Anisotropic 2D Molecular Magnetic Materials Based on Pentagonal Bipyramidal Heptacyanidorhenate(IV).

The first neutral 2D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data for the polycrystalline samples of Ph4P[{Mn(acacen)}2Re(CN)7]·Solv (1) and PPN[{Mn(acacen)}2Re(CN)7]·Solv (2) have shown that both materials display slow magnetic relaxation at temperatures below 10 and 21 K for 1 and 2, respectively. Despite the presence of the same molecular magnetic modules that make up the anionic layers, the studied 2D networks differ significantly in magnetic anisotropy, having a small coercive field (0.115 T) for 1 and a large one (~2.5 T) for 2 at 2 K. In addition, for both polymers a M(H) value does not saturate at the maximum available field of 7 T, and the material 2 is a metamagnet. This intriguing difference originates from the cooperative anisotropic spin interaction in ReIV-CN-MnIII pairs and the zero field splitting (ZFS) effect of MnIII ions with a noncollinear alignment of the local magnetic axes in crystals of the compounds.

Highlighting Recent Crystalline Engineering Aspects of Luminescent Coordination Polymers Based on F-Elements and Ditopic Aliphatic Ligands.

Three principal factors may influence the final structure of coordination polymers (CPs): (i) the nature of the ligand, (ii) the type and coordination number of the metal center, and (iii) the reaction conditions. Further, flexible carboxylate aliphatic ligands have been widely employed as building blocks for designing and synthesizing CPs, resulting in a diverse array of materials with exciting architectures, porosities, dimensionalities, and topologies as well as an increasing number of properties and applications. These ligands show different structural features, such as torsion angles, carbon backbone number, and coordination modes, which affect the desired products and so enable the generation of polymorphs or crystalline phases. Additionally, due to their large coordination numbers, using 4f and 5f metals as coordination centers combined with aliphatic ligands increases the possibility of obtaining different crystal phases. Additionally, by varying the synthetic conditions, we may control the production of a specific solid phase by understanding the thermodynamic and kinetic factors that influence the self-assembly process. This revision highlights the relationship between the structural variety of CPs based on flexible carboxylate aliphatic ligands and f-elements (lanthanide and actinides) and their outstanding luminescent properties such as solid-state emissions, sensing, and photocatalysis. In this sense, we present a structural analysis of the CPs reported with the oxalate ligand, as the one rigid ligand of the family, and other flexible dicarboxylate linkers with -CH2- spacers. Additionally, the nature of the luminescence properties of the 4f or 5f-CPs is analyzed, and finally, we present a novel set of CPs using a glutarate-derived ligand and samarium, with the formula [2,2'-bipyH][Sm(HFG)2 (2,2'-bipy) (H2O)2]•(2,2'-bipy) (α-Sm) and [2,2'-bipyH][Sm(HFG)2 (2,2'-bipy) (H2O)2] (ß-Sm).

Cu(C3H3N3S3)3 Adsorption onto ZnTiO3/TiO2 for Coordination-Complex Sensitized Photochemical Applications.

Currently, the design of highly efficient materials for photochemical applications remains a challenge. In this study, an efficient semiconductor was prepared, based on a coordination complex (Cu-TTC) of Cu(I) and trithiocyanuric acid on ZnTiO3/TiO2 (ZTO/TO). The Cu-TTC/ZTO/TO composite was prepared by the solvothermal method at room temperature. The structural, optical, and electrochemical characteristics, as well as the photocatalytic performance of the composite, were experimentally and computationally studied. The results show that the Cu-TTC/ZTO/TO composite efficiently extended its photoresponse in the visible region of the electromagnetic spectrum. The electrochemistry of the proposed tautomeric architecture (s-Cu-TTC) clearly reveals the presence of metal-ligand charge-transfer (MLCT) and π → π* excitations. The maximum methylene blue (MB) dye photodegradation efficiency of 95% in aqueous solutions was achieved under the illumination of simulated solar light. Finally, computational calculations based on the Density Functional Theory (DFT) method were performed to determine the electronic properties of the s-Cu-TTC tautomeric structure and clarify the adsorption mechanism of this complex on the surface (101) of both ZnTiO3 and TiO2 oxides. The results obtained allow us to suggest that the Cu-TTC complex is an effective charge carrier and that the Cu-TTC/ZTO/TO composite can be used efficiently for photochemical applications.

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers.

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

Data of synthesis, characterization and luminescence measurements in 1D lanthanide coordination polymers based on lanthanides.

In this work are presented all the conditions of synthesis explored to obtain a new family of compound with formula [Ln(4-OHBBA)3(H2O)2] (Ln = La, Pr). Powder X ray diffraction was used to identify the different phases obtained in the synthetic study. FT-IR spectroscopy and TG analysis for La and Pr pure phases are also reported. Optical properties of optically active CPs materials, solid state photoluminescence properties of La, Pr, La-(5%Eu) and La-(5%Tb) compounds were explored. We report the absorption, excitation and emission spectrum of the 4'-hydroxi-4-biphenylcarboxylic acid and a comparative description of the radiative (and no-radiative) processes in solid state in Ln-(4-OHBBA) and Ln-BPDC compounds. Finally, a principal component analysis was conducted in order to take in account both signal contributions from the sensor (LCE at 384 nm and the europium emission at 610 nm) and for classifying the type of analytes used to test the sensing response of the materials.

Two new mixed-ligand coordination polymers based on multi-N chelating ligand inhibit YAP expression and induce caspase-mediated spinal tumor cell apoptosis

Two new coordination polymers [Zn (bdc)(bpybzimH2)](DMF)0.5 (1, H2bdc=1,4-dicarboxybenzene, bpybzimH2=6,6′-bis-(1H-benzoimidazol-2-yl)-2,2′-bipyridine, DMF=N,N-dimethylformamide) and [Co (bpybzimH2)(sbc)]H2O (2, H2sbc=4-mercaptobenzoic acid) have been successfully prepared under solvothermal conditions using the multi-N chelating organic ligand bpybzimH2 as the foundational building block. In addition, the Cell Counting Kit-8 assay was conducted to evaluate the anti-proliferation activity of compounds 1 and 2 against human spinal tumor cells OPM-2. The cell viability curves showed that the two compounds have anti-proliferation activity on spinal tumor cells, and the activity of compound 1 is higher than compound 2. The annexin V-FITC/PI assay and western blot were used to detect the apoptotic percentage of OPM-2 cells incubated with compounds 1 and 2. The YAP protein expression and its role in cell apoptosis were further studied with qRT-PCR, immunoblotting, and flow cytometer.

Coordination Polymers Containing 1,3-Phenylenebis-((1H-1,2,4-triazol-1-yl)methanone) Ligand: Synthesis and ε-Caprolactone Polymerization Behavior.

The reaction of isophthaloyl dichloride with 1H-1,2,4-triazole afforded the new ligand 1,3-phenylenebis(1,2,4-triazole-1-yl)methanone (1). A series of Co(II), Cu(II), Zn(II) and Ni(II) complexes were synthesized using 1 and then characterized by melting point analysis, elemental analysis, theoretical calculations, thermogravimetric analysis, X-ray powder diffraction, nuclear magnetic resonance, infrared and Raman spectroscopy. Experimental and computational studies predict the formation of coordination polymers (CPs). The cobalt and copper CPs and zinc(II) complex were found to be good initiators for the ring-opening polymerization of ε-caprolactone (CL) under solvent-free conditions. ¹H-NMR analysis showed that the obtained polymers of CL were mainly linear and had terminal hydroxymethylene groups. Differential scanning calorimetry showed that the obtained polycaprolactones had high crystallinity, and TGA showed that they had decomposition temperatures above 400 °C. These results provide insight and guidance for the design of metal complexes with potential applications in the polymerization of CL.

Three isotypic polymeric complexes with rare earth cations, but-2-enoate anions and 4,4'-(ethane-1,2-diyl)dipyridine and 4,4'-(ethene-1,2-diyl)dipyridine bridging ligands.

Three isotypic rare earth complexes, catena-poly[[aquabis(but-2-enoato-κ(2)O,O')yttrium(III)]-bis(µ-but-2-enoato)-κ(3)O,O':O;κ(3)O:O,O'-[aquabis(but-2-enoato-κ(2)O,O')yttrium(III)]-µ-4,4'-(ethane-1,2-diyl)dipyridine-κ(2)N:N'], [Y2(C4H5O2)6(C12H12N2)(H2O)2], the gadolinium(III) analogue, [Gd2(C4H5O2)6(C12H12N2)(H2O)2], and the gadolinium(III) analogue with a 4,4'-(ethene-1,2-diyl)dipyridine bridging ligand, [Gd2(C4H5O2)6(C12H10N2)(H2O)2], are one-dimensional coordination polymers made up of centrosymmetric dinuclear [M(but-2-enoato)3(H2O)]2 units (M = rare earth), further bridged by centrosymmetric 4,4'-(ethane-1,2-diyl)dipyridine or 4,4'-(ethene-1,2-diyl)dipyridine spacers into sets of chains parallel to the [201̄] direction. There are intra-chain and inter-chain hydrogen bonds in the structures, the former providing cohesion of the linear arrays and the latter promoting the formation of broad planes parallel to (010).

Reversible transformation between cubane and stairstep Cu4I4 clusters using heat or solvent vapor.

The controlled self-assembly of CuI and an asymmetric ligand with mixed N/S donors, 2-(tert-butylthio)-N-(pyridin-3-yl)acetamide (L), afforded three Cu(I) coordination polymers (CPs), [Cu4I4L2(MeCN)2]n (1), [Cu4I4L2]n (2), and {[Cu4I4L2]⋅MeOH}n (3). X-ray analyses showed that CPs 1-3 are supramolecular isomers with 1, 2, and 3D structures, respectively. CP 1 adopts a stairstep Cu4I4 cluster, whereas CPs 2 and 3 are composed of cubane-like Cu4I4 clusters. Crystal-to-crystal transformations of 1 to 2 and 3 showed reversible transformations between different Cu4I4 clusters using heat or solvent (acetonitrile or methanol) vapor. CP 2 was reversibly transformed to 3 by the addition of methanol and heat. Therefore, the transformations between supramolecular isomers 1, 2, and 3 are completely reversible.