1D Polymeric Structure Research Articles

Determination of compressive strength of 3D polymeric lattice structure as template in powder metallurgy

Powder metallurgy has been developed to fabricate metal foams from various materials including magnesium. One particular challenge on powder metallurgy is fabrication of highly-ordered and interconnected porous products. Pores interconnectivity is important in application of porous magnesium alloy for biodegradable orthopedic implants. Meanwhile, 3D polymeric printing technology offers capability to build precise and rapid lattice wireframe products in a simple and low-cost manner. Here, we design and validate the capability of 3D polymeric lattice as template in powder metallurgy for fabrication of magnesium-based biodegradable implants. Lattice structures were made of ABS, PLA, and PVA filaments. Lattice structures were cubical-shaped with uniform dimension and variations in pore size are included in the study. Both computational and experimental tests are performed to determine the compressive strength of the lattice structures. Uniaxial stress with uniform magnitude is applied to test the lattice structures. The resulting stress, strain, and deformation of the 3D polymeric lattice are observed. Variations in materials and pore size affect the stress, strain and deformation of the 3D polymeric lattice. Parameters can be further optimized to meet the requirement of the design and fabrication process in consideration of the tolerable stress, strain and deformation.

Structural Analysis of Polymeric Copper(II)–Pyrazinamide Complexes Prepared from Two Different Copper(II) Salts

In crystal engineering, the presence of different types of anion may alter the structure of transition metal complexes. Thus, the anions may also govern the properties of the metal complexes. Hereby we reported a structural analysis of polymeric copper(II)-pyrazinamide (pza) complexes prepared from copper(II) sulphate and copper(II) chloride. The complexes were crystallised using a bench-top technique with copper(II):pza molar ratio of 1:2 in a layered H2O-CH3OH solvent at room temperature. Single crystal XRD, ATR-IR and melting point apparatus were used to analyse the structure and characterise the complexes. Single crystal XRD analyses reveals that both complexes, [Cu( µ-pza)(SO4)(H2O)2]n (A) and [Cu(pza)2( µ-Cl)2]n (B) forms a 1D polymeric structure with different metal-ligand connectivity around the octahedral copper centre. The copper centres are also linked by different ligand, namely pyrazinamide in A and chloride in B. Thus, the Cu…Cu distances in both complexes are different, 6.719 Å in A and 3.658 Å in B. Unlike in A, the crystal structure of B has two unique copper centres. In addition, crystal structures of A and B were also compared to closely related copper(II)-pza complexes from published literature. As also observed in many metal complexes, crystal structures of copper(II)-pza complex were affected by the anion of the metal salts used in the reaction, in which the anion also involves in the crystal structures.

Solution Studies and Crystal Structures of Heteropolynuclear Potassium/Copper Complexes with Phytate and Aromatic Polyamines: Self-Assembly through Coordinative and Supramolecular Interactions.

Phytate (L12- ) is a relevant natural product. It interacts strongly with biologically relevant cations, due to the high negative charge exhibited in a wide pH range. The synthesis and crystal structures of the mixed-ligand Cu(II) polynuclear complexes K(H2 tptz)0.5 [Cu(H8 L)(tptz)] ⋅ 3.6H2 O (1), K(H2 O)3 {[Cu(H2 O)(bpca)]3 (H8 L)} ⋅ 1.75H2 O (2), and K1.5 (H2 O)2 [Cu(bpca)](H9.5 L) ⋅ 8H2 O (3) (tptz=2,4,6-tri(pyridin-2-yl)-1,3,5-triazine; Hbpca=bis(2-pyridylcarbonyl) amine) are reported herein. They were obtained by the use of an aromatic rigid amine, which satisfies some of the metal coordination sites and promotes the hierarchical assembly of 2D polymeric structures. Speciation of phytate-Cu(II)-Hbpca system and determination of complex stability constants were performed by means of potentiometric titrations, in 0.15 M NMe4 Cl at 37.0 °C, showing that, even in solution, this system is able to produce highly aggregated complexes, such as [Cu3 (bpca)3 (H7 L)]2- . Furthermore, the Cu(II)-mediated tptz hydrolysis was studied by UV-vis spectroscopy at room temperature in 0.15 M NMe4 Cl. Based on the equilibrium results and with the aid of molecular modelling tools, a plausible self-assembly process for 2 and 3 could be proposed.

Elastic organic crystals of π-conjugated molecules: anisotropic densely packed supramolecular 3D polymers exhibit mechanical flexibility and shape tunability

π-Conjugated molecules have attracted much attention over recent years and have applications in various organic devices. Single crystals of these molecules are attractive materials for developing unique and/or high-performance devices owing to their anisotropic densely packed supramolecular 3D polymer structures. However, they are not flexible and are therefore not suitable for wearable devices. In this focus review, the author’s recent work on flexible crystals involving designing fibril lamella of slip-stacked molecular wires based on planar π-conjugated molecules and their applications is summarized. Unlike common organic crystals, 1,4-bis[2-(4-methylthienyl)]-2,3,5,6-tetrafluorobenzene exhibits elastic bending flexibility with π-functionality. This supramolecular 3D polymer design concept offers top–down synthesis of crystalline fibers and films. Moreover, the functionality and flexibility of such a crystal realizes both high-performance flexible fluorescent waveguide and reversible mechanofluorochromic behavior. Finally, the interesting shape-tunable supramolecular formation of a fluorescent π-conjugated polymer containing a 1,4-bis[2-(4-hexylthienyl)]-2,3,5,6-tetrafluorobenzene repeating unit is described. This focus review describes that “elastic organic crystals of π-conjugated molecules”. The author developed the field of innovative materials for flexible optoelectronics. Intentional design of intramolecular interaction in π-system furnish the flexible crystals. These crystals show not only elastic bending flexibility and shape tunability but also functionality for mechanical sensors and flexible optical waveguide.

Lanthanoid Heteroleptic Complexes with Cucurbit[5]uril and Dicarboxylate Ligands: From Discrete Structures to One-Dimensional and Two-Dimensional Polymers.

Lanthanoid heteroleptic complexes with cucurbit[5]uril {Q[5]} and two dicarboxylate ligands, e.g., diglycolic acid (H2DGC) and glutaric acid (H2GT), have been investigated with six new compounds featuring a tetrametallic and dimetallic discrete structures, a one-dimensional (1D) polymer, and three two-dimensional (2D) polymers with a unique honeycomb-type topology being synthesized and structurally characterized. [La4(Q[5])3(DGC)2(NO3)2(H2O)12][La(DGC)(H2O)6]·7NO3· nH2O (1) has a tetrametallic structure constructed with three bis-bidentate Q[5] ligands linking two [La(DGC)(H2O)2]+ species in the middle and two [La(H2O)4(NO3)]2+ species at both ends. [Ce2(Q[5])(DGC)(NO3)(H2O)10]·3NO3·4H2O (2) has a dimetallic structure built up with a bis-bidentate Q[5] ligand linking [Ce(DGC)(H2O)3(NO3)] and [Ce(H2O)7]3+ on each side of the Q[5] portals. [Ce3(Q[5])3(DGC)2(H2O)9][Ce(DGC)(H2O)6]2·7NO3· nH2O (3) has a 1D polymeric structure built up with bis-bidentate Q[5] ligands in-turn linking one [Ce(H2O)6]3+ and two [Ce(DGC)(H2O)6]1+ cationic species. [Ln2(Q[5])2(GT)(H2O)6]·4NO3· nH2O [Ln = La (4), Ce (5) and Nd (6)] have similar 2D polymeric structures built up with two types of 9-fold coordinated Ln polyhedra linked by Q[5] via bis-bidentate carbonyl groups on both sides forming 1D chains which are further connected by bridging GT2- ligands to form 2D polymers with a unique honeycomb-type topology. Their vibrational modes and electronic structures have also been investigated.

Synthesis of Ether-Functionalized and Sterically Demanding Molybdenum Alkylidyne Complexes

The synthesis of ether-functionalized molybdenum benzylidyne complexes [ArC≡Mo{OC(CF3)2Me}3] (6, Ar = para-methoxyphenyl; 7, Ar = 2,4,6-trimethoxyphenyl) and of the sterically demanding benzylidyne complex [{2,4,6-(i-Pr)3C6H2}C≡Mo{OC(CF3)2Me}3] are presented, together with their spectroscopic characterization, molecular structures, and catalytic activity in alkyne metathesis. Complexes 6 and 7 feature intermolecular contacts between the para-methoxy group and the molybdenum center that give rise to 1D-polymeric structures in the solid state. The preparation of other functionalized alkylidyne complexes, [ArC≡Mo{OC(CF3)2Me}3] (Ar = 2-(i-PrO)C6H4, 8-MeO-Naph, 2,6-(i-Pr)2C6H3), was also attempted, but only the acyl precursors [ArC(═O)Mo(CO)5]− could be isolated. The synthesis of the molybdenum acyl complexes was challenging, and appropriate alternative protocols were developed.

Studies on the structural diversity of MOFs containing octahedral siloxane-backboned connectors

Four metal–organic frameworks containing hexatopic connectors have been prepared and structurally characterised: [Cd3(L)(DMA)2(H2O)2] (IMP-28), [Ce2(L)(DMF)2(H2O)2] (IMP-29), [Y2(L)(DMF)2(H2O)2] (IMP-30), and [Zn2(L-H2)(4,4′-bipy)2] (IMP-31). All the MOFs have been constructed using the hybrid inorganic–organic siloxane linker hexakis(4-carboxyphenyl)disiloxane (L-H6). In each case, discrete metal-based nodes are cross-linked by the octahedrally disposed connector to afford 3D polymeric structures. The underlying nets in these MOFs have been evaluated through deconstruction of their crystal structures and subsequent topological analysis. Examples of MOFs built from hexatopic linkers, and especially those with octahedral predispositions such as in L, remain scarce and the topologies ascribed to some of these MOFs are unique.

Investigation of structural, spectral and thermal properties of one-dimensional polymer containing pyromellitic acid and isonicotinamide

The coordination polymer with mixed ligand [Cu2(H2O)2 (pm) (ina)2]n.3nH2O (pm = tetraanion of pyromellitic acid, ina = isonicotinamide) was studied mostly on its supramolecular architecture. Single crystals were synthesized and structural properties of the 1D polymer were characterized by Single Crystal X-ray diffraction (SCXRD), different spectroscopic methods (Infrared (IR) spectroscopy, UV–Vis spectroscopy and EPR spectroscopy), Thermal and Elemental analysis. It has been observed that complex has crystallized in the monoclinic space group P21/c. The geometric environment of Cu(II) ion is five-coordinated in slightly distorted square pyramidal geometry and τ value have found 0.13. The pyromellitate ligands connecting the metal centers act as bridge and form 1D polymer chains of 2,4 ribbon type [1]. The ladder-like polymer is connected by OH⋯O and NH⋯O hydrogen bonds to form supramolecular building. This complex consists of a 3D polymeric structure with containing planar hexacyclic and dimeric water rings. It was mainly focused on the characteristic (COO)as and (COO)s stretching vibrations of pyromellitate anion in the FT-IR investigation of the complex.

Catalytic 3D polymerization of C60

ABSTRACTThe present study addresses the problems of catalytic synthesis of C60-based 3D polymers in the presence of carbon disulfide CS2. It is shown that CS2 lowers the pressure of fullerite 3D polymerization at room temperature. In particular, the pressure at which the 3D ultrahard fullerite C60 phase is formed decreases from 18 GPa to 7 GPa. The catalyst plays no significant role at room temperature and low pressures up to 6 GPa. When the C60 + CS2 is heated to 1200 K, the pressure of the 3D C60 polymerization is further reduced to 2–4 GPa. Based on the TEM data, we propose a 3D polymer structure based on C60 obtained by the catalytic synthesis.

Thorium(IV) and Uranium(IV) Complexes with Cucurbit[5]uril.

Tetravalent thorium and uranium complexes with cucurbit[5]uril (Q[5]) were investigated with eight new complexes being synthesized and structurally characterized. [Th(Q[5])(OH)(H2O)2]6·18NO3· nH2O (1) has a hexagonal nanowheel structure with each of the six Th4+ ions being cap-coordinated by a Q[5] and monodentate-coordinated to the nearby Q[5]. [Th(Q[5])(HCOO)(H2O)4][Th(NO3)5(H2O)2]2[Th(NO3)3(HCOO)(H2O)2]0.5·NO3· nH2O (2) has a heteroleptic mononuclear structure with a Th4+ ion cap-coordinated on one side of the Q[5] portal and monodentate-coordinated to a formate anion inside the Q[5] cavity. [KTh1.5(Q[5])Cl(NO3)3][Th(NO3)5(H2O)2]·2NO3·2.5H2O (3) has a heterometallic structure with both Th4+ and K+ ions each occupying one side of the two Q[5] portals forming a capsule. [CsTh(Q[5])Cl(NO3)2(H2O)3]·2NO3· nH2O (4) has a heterometallic 1D polymeric structure with both Th4+ and Cs+ ions each occupying one side of the two Q[5] portals, forming monomers which are linked together by sharing two water molecules and one carbonyl oxygen atom between Th4+ and Cs+ ions. [Th(Q[5])Cl(H2O)][CdCl3][CdCl4]·0.5HCl·4H2O (5), [Th(Q[5])Cl(H2O)][Ru2OCl9(H2O)]·0.5HCl·9.5H2O (6), [Th(Q[5])Cl(H2O)][IrCl6]1.5·3H2O (7), and [U(Q[5])Cl(H2O)][ZnCl3(H2O)][(ZnCl4)]·8H2O (8) have similar 1D polymeric structures with Th4+/U4+ ions cap-coordinated on one side of a Q[5] and bidentate coordinated to the nearby Q[5]. The transition metal chlorides act as anions for charge compensation as well as structure inducers via cation-anion interactions forming various anion patterns around the 1D polymers. Actinide contraction has been observed in the early actinide series.

Nickel(II) based homo- vs heterometallic 1D coordination polymers derived from a novel 6-aminouracil building block: Structures, topologies, non-covalent interactions, magnetism, and antibacterial activity

A new azo-ligand, 1,3-dimethyl-5-(p-carboxy-phenylazo)-6-aminouracil (H3L) containing 6-aminouracil (a biomolecule) and a carboxylic function (a potential linker) was synthesized. This ligand was then employed for complexation with Ni(II), resulting in the Ni(II)/Na(I) heterometallic {[NiNa2(μ-HL)2(μ-H2O)2(H2O)6]·6H2O}n(1) and Ni(II) homometallic {[Ni2(μ-HL)2(H2O)4]·5·.5H2O}n(2) 1D coordination polymers. These were obtained from similar reaction mixtures and conditions, except the type of the base (NaOH for 1 or KOH/Et3N for 2). Compounds 1 and 2 were characterized by single-crystal X-ray diffraction, UV-vis, NMR, and IR spectroscopy. Both the coordination polymers 1 and 2 show resembling zigzag chains that are topologically classified as 2-connected underlying nets with the 2C1 topology. In 1, the 1D metal-organic chains are further extended by intermolecular H-bonds, giving rise to a 3D H-bonded net; it is topologically described as a uninodal 6-connected net with the pcu topology. In solution, the 1D polymeric structures of both compounds disaggregate into monomeric Ni(II)-square-planar complex units [Ni(HL)2]2−, as evidenced by NMR and UV-vis spectroscopy studies. The magnetic properties of 2 were also investigated, indicating a dominant zero field splitting parameter D of the Ni(II) center. The type of the base is important for tuning the selective formation of the desired product 1 or 2. Density functional theory (DFT) study justifies the experimental findings for a base-assisted selectivity between the compounds 1 or 2 by optimizing their structures at the PBE-D/DNP level of theory. The existence of agostic interactions between the CH bonds of the methyl groups of the coordinated HL2− moieties and the Ni centers in both structures is suggested by natural bond orbital (NBO) calculations at the M06-2X/6-31 + G∗ level of theory. The compound 1 proves to be a potential inhibitor of a bacterial virulence factor, pyocyanin.

Three interpenetrating coordination polymers with 3D honeycomb networks derived from versatile ligand: 4'-(4-pyridyl)-4,2':6′,4″-terpyridine

Three interpenetrating Co(II)/Ni(II) coordination polymers, [Co(pytpy)(sfdb)]n (1), [Co2(pytpy)(sfdb)2]n (2) and [Ni(pytpy)(sfdb)]n·nH2O (3) (pytpy = 4'-(4-pyridyl)-4,2':6′,4″-terpyridine, H2sfdb = 4,4′-sulfonyldibenzoic acid) have been hydrothermally synthesized and structurally characterized. They all feature interpenetrating 3D honeycomb networks. Compound 1 is a 4-fold 3D polymeric structure, bidentate-bridging pytpy ligands join the square wave-like chains based on Co(II) centers and μ2-sfdb2- linkers to form the final 3D honeycomb network. Compound 2 is also a 3D honeycomb structure, which features 2-fold interpenetrating structure with unusual paddle-wheel secondary building units (SBUs). The topological net of compound 3 is identical to 1, but the central metal and its coordination environment are different from those of compound 1. In addition, diffuse reflectance UV–vis spectroscopic measurements and thermal gravimetry analyses have been used to characterize these compounds.

Efficient Bio-Inspired Oxygen Reduction Electrocatalysis with Electropolymerized Cobalt Corroles

Fuel cells are considered as the only viable solution for long-range electromobility, but very rare and expensive platinum is currently required for catalyzing the bottleneck reaction therein: oxygen reduction. Within the search for catalysts that are not based on precious metals, cobalt corroles were uncovered to fulfill the requirements of high selectivity and low overpotential. We now report on the electropolymerization of a specifically designed catalyst, a cobalt(III) complex of tris(4-aminophenyl)corrole, upon which 3D polymeric structures were obtained. Much better catalytic activity was obtained by this approach in comparison to monomeric catalyst, manifested by significantly lower overpotentials, as well as higher selectivity to the desired 4e–/4H+ pathway. The performance in an alkaline environment makes it the most active molecular catalyst for the oxygen reduction reaction reported to date.

Synthesis and hydrogen bonded 3D polymeric structure of new compound based on 2-amino-1,4-benzene dicarboxylic acid and 4,4-bipyridine

Yeni bileşik, [NH2-BDC][4,4-bpy], (NH2-BDC = 2-amino-1,4-benzen dikarboksilik asit, 4,4-bipy = 4,4-bipiridin) sentezlendi ve tek kristal X-ışını kırınım metodu ile karakterize edildi. Kristalin yapısal analizi bileşiğin monoklinik uzay grubu I 2/a ile kristallendiği ve asimetrik biriminin iki yarım 2-amino-1,4-benzen dikarboksilik asit ve 4,4-bipiridin molekülü içerdiğini ve yapıda 1:1 oranında kristal oluşturduğunu göstermektedir. NH2-BDC molekülü simetri merkezi üzerinde yer alırken 4,4-bipy molekülü iki katlı dönme ekseninde bulunmaktadır. Kristal yapıda, moleküller üç adet kuvvetli molekül içi ve moleküler arası O–H···N ve O–H···O hidrojen bağları ile bir arada tutunurlar ve 3D kristal yapısını oluşturur. Hidrojen bağlı polimerik ağ bc düzleminde paketlenir ve a ekseni boyunca istiflenir. Buna ek olarak, kristal C–H···O tip zayıf hidrojen bağı ile daha kararlı hal alır. Kristal paketlenmesinde aromatik halkaların bir merkezden diğer merkeze 3.740(2) Å uzaklığa sahip p–p etkileşmelerinin olduğu görülür. Sarı renkli azot pigmentlerinden olan [NH2-BDC][4,4-bpy] bileşiği endüstriyel üretimde bir ara madde olarak kullanılabilir.

Tunable luminescent behaviors of Ag-containing metal coordination polymers with N-heterocyclic and sulfonate group

Three new metal coordination polymers, namely, [Ag(BPYE)(BS)] (1), [Ag2(BPY)2(BS)(NO3)(H2O)2]·H2O (2), and [Ag2(BPY)2(ABS)(NO3)]·H2O (3) [BS = benzenesulfonate, BPYE = 1,2-bi(4-pyridyl)ethene, BPY = 4,4′-bipyridine, ABS = p-aminobenzenesulfonate], have been obtained under solvothermal conditions, which were structurally characterized by X-ray single-crystal diffraction, EA, PXRD, FT-IR, thermogravimetry analysis (TGA) and differential scanning calorimetric (DSC). These complexes show a one-dimensional (1D) polymeric structure, which will further be constructed a three-dimensional (3D) supramolecular framework via hydrogen bonding, π⋯π stacking interactions and CH⋯π interactions. The shortest distances of π⋯π packing interactions of complexes 1–3 are 3.644, 3.558 and 3.780 Å, respectively. The luminescent properties of complexes 1–3 were investigated in the solid state at room temperature, where the maximal emission peaks can be observed at 418 (λex = 350), 364 (λex = 320) and 474 nm (λex = 364 nm), respectively. Obviously, the emission maxima are proportional to the intermolecular π⋯π packing distances.

Sub-micrometer Sized, 3D-Surface-attached Polymer Networks by Microcontact Printing: Using UV-Crosslinking Efficiency to Tune Structure Height.

The lateral dimensions of micro- and nanostructures obtained by microcontact printing (μCP) can be easily varied by selecting stamps with the desired spacing and pattern. However, the height of these structures cannot be tuned as easily, and in most cases only 2D structures are obtained. Here, we show how the chemical cross-linking properties of polymer inks designed for μCP can be used to obtain 3D structures with heights ranging from 3 to 750 nm using the same μCP stamps. This is technologically relevant because the ink concentration affects the quality and resolution of the printed image, and therefore can only be varied in a certain range. By exploiting the cross-linking efficiency to tune the height, an additional parameter is available to reach the desired structure height without compromising the image quality. The inks were made from copolymers containing a low percentage of different UV cross-linkable repeat units: nitrobenzoxadiazole (NBD), coumarin (COU), and/or benzophenone (BP). The base polymer of the here presented model system was an antimicrobially active poly(oxanorbornene) (SMAMP), however the concept should be transferable to many other polymer backbones. We describe the fabrication and characterization of the printed micro- and nanostructures made from pure SMAMP, NBD-SMAMP, coumarin-SMAMP, BP-SMAMP, BP-NBD-SMAMP and BP-coumarin-SMAMP polymer inks. The photo-dimerization of COU during UV irradiation at λ = 254 nm was confirmed by UV-Vis spectroscopy. Since NBD and COU are fluorescent, the polymer could be visualized by fluorescence microscopy. Additionally, their height profiles were measured by atomic force microscopy (AFM). The heights of the 3D surface-attached polymer networks obtained from the here presented polymer inks correlated with the gel-content of the corresponding unstructured polymer layers, and thus with the cross-linking efficiency of the NBD, COU and BP cross-linkers. Due to being covalently cross-linked, these 3D-surface attached polymer structures were solvent-stable and stable in aqueous surroundings.

Zinc and copper complexes of stilbene iminopyridine ligands with η2-Olefin binding mode

Two stilbene based iminopyridine ligands (L1-L2) synthesized by a condensation reaction between N,N-Dimethyl-4,4′-azodianiline and 2-pyridinecarboxaldehyde or 2,6-pyridinedicarboxaldehyde, with 73% and 65% yield, are described. The two ligands have been characterized by elemental analysis and spectroscopic techniques. The complexation of ligand L1 with ZnCl2 afforded neutral tetrahedral zinc(II) metal complex C1 formulated as [ZnL1Cl2] with a 2D supramolecular architecture reinforced by π···π stacking and hydrogen bonding in the solid state. Interestingly in the case of copper(I) complex C2, ligand L1 acts as a ditopic ligand since it coordinates one Cu(I) with an iminopyridyl fragment and a second metal center with an η2-olefin binding mode giving rise to a 1D-polymeric structure. The coordination sphere is completed with an acetonitrile solvent molecule leading to a distorted tetrahedral geometry around copper cation and the resulting coordination polymer can be formulated as {[Cu(L1)2CH3CN]BF4}. In addition complexation of L2 with zinc chloride afforded complex C3 formulated as [ZnL2Cl2]. DFT and TDDFT computations permitted to investigate the frontier MOs of all species and to assign their UV–visible absorption bands.

Tunable mechanical properties of stent-like microscaffolds for studying cancer cell recognition of stiffness gradients

Physical and mechanical properties of extracellular matrix (ECM) have been proved to be crucial in the metastatic process. However, currently available studies on the interplay between ECM stiffness and cancer cell invasive behaviour are performed on planar assays, while the in vivo interaction takes place in three-dimensions. To take into consideration the ECM structural and mechanical complexity in the cell/structure interactions, we fabricated 3D microscaffolds through two-photon lithography (2PL) and tested how they are invaded by human colorectal adenocarcinoma (LS-174T) tumor cells, showing that it is possible to detect significant differences in cells/structure interaction when structural parameters are modified. In particular, both scaffold geometry and 2PL fabrication parameters were optimized to obtain 3D polymeric cylindrical structures with controlled Young's modulus and with linear stiffness gradients. The ability of LS-174T to migrate in the scaffolds was tested in different experimental conditions, including scaffolds functionalization and under β-catenin downregulation. It was observed that high Young's modulus scaffolds are always less invaded than softer ones, confirming the role of the 3D micro-environmental stiffness in mediating cells migration, including when specific functionalization or pharmacological treatments are performed.

Coordination Polymer of M(II)-Pyrazinamide (M = Co, Cd) with Double End-to-End Thiocyanate Bridge

Pyrazinamide (pza, C4N2H3-CONH2) is a good ligand for coordination polymer. Their transition metal complexes are known to have antibacterial activities, magnetic properties, etc. Coordination polymers of M(II)-pyrazinamide with thiocyanate (M = Co (a), Cd (b)), prepared using bench-top layering technique with M(II):pza:SCN ratio of 1:2:2, is successfully crystallised at room temperature. Single crystal XRD was used to determine the crystal structure. Infrared and melting point determination were also performed. Crystal structure of both complexes, solved in Triclinic P-1, show that each octahedral metal centre is connected to two adjacent metal centres by double end-to-end thiocyanate bridge forming a 1D polymeric structure with M···M distances of 5.524 Å (in a) and 5.887 Å (in b). Two monodentate pyrazinamide ligands occupy the rest of the coordination sites on the metal centre in a trans relationship. Only in complex a, one lattice pyrazinamide molecule is involved in the asymmetric unit. Crystal packing of both a and b are also displaying non-covalent networks as a result of hydrogen-bonding involving the pyrazine ring, amide and carbonyl groups between adjacent chains and π···π interactions (only occurred in a). In addition, the observed melting points of both a and b are relatively close to each other (around 180°C), and ATR-IR spectra support the presence of the bridging thiocyanate and terminal pyrazinamide.

One-dimensional coordination polymers of whole row rare earth tris-pivalates

Fourteen 1D coordination polymers of rare earth pivalates [Ln(Piv)3]∞ (Ln = Y, La, Pr, Nd, Sm−Lu) were synthesized and characterized by powder X-ray diffraction, IR spectroscopy, TGA, and conventional elemental analysis. Crystal structures of [La(Piv)3]∞, [Yb(Piv)3]∞, [Lu(Piv)3]∞ were determined by means of single crystal X-ray analysis at 120K, those of [Y(Piv)3]∞ and [Ho(Piv)3]∞ — from powder XRD data at 293K. Transformation of [Ln(Piv)3]∞ structure and Piv– anions coordination mode along the whole row has been derived from powder XRD and IR spectroscopy results, and shown to crucially affect the relative location of 1D chains in the crystal structure, as well as the Ln···Ln distance within the single chain. Negative thermal expansion along 1D [Ln(Piv)3]∞ chain was revealed for Ln = Tm, Yb, Lu. Enforcement of 1D polymeric structure with the decrease of Ln ionic radius has been established from solid-state DFT calculations.