Achieving large thermal hysteresis in an anthracene-based manganese(II) complex via photo-induced electron transfer

Achieving magnetic bistability with large thermal hysteresis is still a formidable challenge in material science. Here we synthesize a series of isostructural chain complexes using 9,10-anthracene dicarboxylic acid as a photoactive component. The electron transfer photochromic Mn²⁺ and Zn²⁺ compounds with photogenerated diradicals are confirmed by structures, optical spectra, magnetic analyses, and density functional theory calculations. For the Mn²⁺ analog, light irradiation changes the spin topology from a single Mn²⁺ ion to a radical-Mn²⁺ single chain, further inducing magnetic bistability with a remarkably wide thermal hysteresis of 177 K. Structural analysis of light irradiated crystals at 300 and 50 K reveals that the rotation of the anthracene rings changes the Mn1–O2–C8 angle and coordination geometries of the Mn²⁺ center, resulting in magnetic bistability with this wide thermal hysteresis. This work provides a strategy for constructing molecular magnets with large thermal hysteresis via electron transfer photochromism.

Achieving magnetic bistability with large thermal hysteresis is still a challenge in material science. Here, the authors report a Mn(II) chain complex that enables light-induced magnetic bistability with a 177 K thermal hysteresis loop.

Zn- and Cd-based coordination polymers with a novel anthracene dicarboxylate ligand for highly selective detection of hydrogen peroxide

A one-dimensional {[Zn(L)(DMF)2]}n (1) and a three-dimensional {[Cd(L)(DMF)]·DMF}n (2) coordination polymer based on the novel anthracene derivative H2L (H2L = 4,4'-(9,10-anthracenediyl)dicinnamic acid) were obtained by solvothermal synthesis and charaterised by single-crystal and powder X-ray diffraction, thermogravimetry, and infrared spectroscopy. The anthracene derivative H2L and coordination polymers 1 and 2 were used to modify a glassy carbon electrode and as such served as an active material for detection of H2O2. Cyclic voltammograms in the potential range from 0 to -0.5 V revealed concentration-dependent cathodic current in all three cases with a lower detection limit of 200 μM. The electrode modified with compound 2 showed the best performance towards hydrogen peroxide detection. The results suggest that the development of electrodes modified with inorganic polymers based on highly conjugated ligands can serve as potential electrocatalytic materials.

Two anthracene chromophore based metal–organic frameworks for gas adsorption and promising nitro aromatic sensing

Two novel metal–organic frameworks (MOFs) have been synthesized under solvothermal conditions. Studies on luminescence sensing show 1 and 2 are highly selective and recyclable in the detection of nitroaromatic explosives, especially for TNP.

[2 + 2] cycloaddition reaction and luminescent sensing of Fe3+ and Cr2O72− ions by a cadmium-based coordination polymer

A cadmium-based coordination polymer can produce the corresponding photoproduct via [2 + 2] cycloaddition reaction, and can detect both Fe³⁺ and Cr₂O₇²⁻ ions.

Luminescent metal–organic frameworks with a 2-(4-pyridyl)-terephthalic acid ligand for detection of acetone

Employing an unsymmetrical pyridyl-dicarboxylate ligand, three MOFs with diverse structures were obtained. The Cd-MOF shows excellent selective sensing towards acetone molecules.

Selective fluorescent sensing and photocatalytic properties of three MOFs based on naphthalene-1,4-dicarboxylic acid and 2,4,5-tri(4-pyridyl)-imidazole

Three MOFs display high sensitivity in the detection of NB and Ca²⁺ or Co²⁺ ions as luminescent probes. Moreover, 3 exhibits a relatively good photocatalytic degradation activity of rhodamine B.

Porous Covalent Triazine Polymer as a Potential Nanocargo for Cancer Therapy and Imaging

A microporous covalent triazine polymer (CTP) network with a high surface area was synthesized via the Friedel-Crafts reaction and employed as a potential transport system for drug delivery and controlled release. The CTP was transformed to the nanoscale region by intense ultrasonication followed by filtration to yield nanoscale CTP (NCTP). This product showed excellent dispersibility in physiological solution while maintaining its chemical structure and porosity. An anticancer drug, doxorubicin (DOX), was loaded onto the NCTP through hydrophobic and π-π interactions, and its release was controlled at pH 4.8 and 7.4. The NCTP showed no toxicity toward cancer or normal cells, but the NCTP-DOX complex showed high efficacy against both types of cells in vitro. In-vitro cell imaging revealed that NCTP is a potential material for bioimaging. The potency of NCTP on cellular senescence was confirmed by the expression of senescence associated marker proteins p53 and p21. These results suggest that NCTP can be used as a new platform for drug delivery and imaging with potential applications in diagnosis and therapy.

Ruthenium(ii)-polypyridyl zirconium(iv) metal-organic frameworks as a new class of sensitized solar cells

A series of Ru(ii)L2L' (L = 2,2'-bipyridyl, L' = 2,2'-bipyridine-5,5'-dicarboxylic acid), RuDCBPY, -containing zirconium(iv) coordination polymer thin films have been prepared as sensitizing materials for solar cell applications. These metal-organic framework (MOF) sensitized solar cells, MOFSCs, each are shown to generate photocurrent in response to simulated 1 sun illumination. Emission lifetime measurements indicate the excited state quenching of RuDCBPY at the MOF-TiO2 interface is extremely efficient (>90%), presumably due to electron injection into TiO2. A mechanism is proposed in which RuDCBPY-centers photo-excited within the MOF-bulk undergo isotropic energy migration up to 25 nm from the point of origin. This work represents the first example in which a MOFSC is directly compared to the constituent dye adsorbed on TiO2 (DSC). Importantly, the MOFSCs outperformed their RuDCBPY-TiO2 DSC counterpart under the conditions used here and, thus, are solidified as promising solar cell platforms.

Tuning different kinds of entangled metal–organic frameworks by modifying the spacer group of aliphatic dicarboxylate ligands and the reactant ratio

Presented here are a series of coordination polymers with different entangled motifs which were synthesized using different dicarboxylic acid ligands and reactant ratios.

Rare earth anthracenedicarboxylate metal–organic frameworks: slow relaxation of magnetization of Nd3+, Gd3+, Dy3+, Er3+ and Yb3+ based materials

We report lanthanide-based MOFs with interesting magnetic behaviours. To the best of our knowledge, Nd³⁺ and Yb³⁺ materials are the first examples of 3D- and 2D-MOFs, respectively, that show slow relaxation of magnetization.

Alkyl group-directed assembly of coordination polymers based on bis-(4-imidazol-1-yl-phenyl)-amine and their photocatalytic properties

Four new coordination polymers have been solvothermally synthesized to explore their diverse networks and photocatalytic properties.

Assembly and Properties of Four New Metal–Organic Complexes Based on 1,4-Naphthalenedicarboxylate: Effect of Four Bis-pyridyl-bis-amide Ligands with Diverse Spacers in the Structures

Four new complexes based on 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) and four bis-pyridyl-bis-amide ligands with various spacers (3-bpye = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane; 3-bpfp = bis(3-pyridylformyl)piperazine; 3-bpcd = N,N′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide; and 3-bpcb = N,N′-bis(3-pyridinecarboxamide)-1,4-benzene), namely [Cu2(1,4-NDC)2(3-bpye)(H2O)] (1), [Cu(1,4-NDC)(3-bpfp)0.5] (2), [Cu3(1,4-NDC)3(3-bpcd)3]·2H2O (3), and [Cu(1,4-NDC)(3-bpcb)] (4), have been hydrothermally synthesized. Complex 1 is a 3D coordination network and represents an 8-connected {420.68} topology. Complex 2 shows a 2-fold interpenetrating 3D architecture with a 6-connected {412.63} topology. Complexes 3 and 4 possess similar 2D sql layers with the {44.62} topology, but the coordination modes of 1,4-NDC ligands and the conformations of the two bis-pyridyl-bis-amide ligands are different. The adjacent layers for 3 and 4 are further linked by hydrogen bonding interactions to form 3D supramolecular networks. The successful assemblies of complexes 1–4 imply that by using the different bis-pyridyl-bis-amide ligands with diverse spacers can produce diverse metal–organic networks. Furthermore, the fluorescence and photocatalytic properties of complexes 1–4 have been investigated.

2D-cadmium MOF and gismondine-like zinc coordination network based on the N-(2-tetrazolethyl)-4′-glycine linker

We have designed and synthesized two new metal-organic-frameworks (MOFs) using the novel N-(2-tetrazolethyl)-4′-glycine spacer (TeGly)²⁻. These materials exhibit intense photoluminescence.

Syntheses, structures, topologies, and luminescence properties of four coordination polymers based on bifunctional 6-(4-pyridyl)-terephthalic acid and bis(imidazole) bridging linkers

Four CPs, with the structure ranged from 2D sheet to 3D 3-fold penetrated net, have been designed with the mixed-ligand strategy of bifunctional 6-(4-pyridyl)-terephthalic acid and bis(imidazole) bridging linkers.

Tunable photoluminescence and direct white-light emission in Mg-based coordination networks

The bpy, dpe and dppe were introduced, respectively, to construct Mg-NDC CPs exhibiting tunable photoluminescence and even direct white-light emission.

The two-dimensional coordination polymer poly[diaqua(μ2-1H-imidazo[4,5-f][1,10]phenanthroline)-μ4-sulfato-μ3-sulfato-dicadmium(II)]

In the title coordination polymer, [Cd2(SO4)2(C13H8N4)(H2O)2]n, there are two crystallographically independent Cd(II) centres with different coordination geometries. The first Cd(II) centre is hexacoordinated by four O atoms of four sulfate ligands, one water O atom and one N atom of a 1H-imidazo[4,5-f][1,10]phenanthroline (IP) ligand, giving a distorted octahedral coordination environment. The second Cd(II) centre is heptacoordinated by four O atoms of three sulfate ligands, one water O atom and two N atoms of one chelating IP ligand, resulting in a distorted monocapped anti-trigonal prismatic geometry. The symmetry-independent Cd(II) ions are bridged in an alternating fashion by sulfate ligands, forming one-dimensional ladder-like chains which are connected through the IP ligands to form two-dimensional layers. These two-dimensional layers are linked by interlayer hydrogen bonds, leading to the formation of a three-dimensional supramolecular network.

NH4FeCl2(HCOO): synthesis, structure, and magnetism of a novel low-dimensional magnetic material

Solvothermal synthesis was used to create a low-dimensional iron(II) chloride formate compound, NH4FeCl2(HCOO), that exhibits interesting magnetic properties. NH4FeCl2(HCOO) crystallizes in the monoclinic space group C2/c (No. 15) with a = 7.888(1) Å, b = 11.156(2) Å, c = 6.920(2) Å, and β = 108.066(2)°. The crystal structure consists of infinite zigzag chains of distorted Fe(2+)-centered octahedra linked by μ2-Cl and syn-syn formate bridges, with interchain hydrogen bonding through NH4(+) cations holding the chains together. The unique Fe(2+) site is coordinated by four equatorial chlorides at a distance of 2.50 Å and two axial oxygens at a distance of 2.08 Å. Magnetic measurements performed on powder and oriented single-crystal samples show complex anisotropic magnetic behavior dominated by antiferromagnetic interactions (TN = 6 K) with a small ferromagnetic component in the direction of chain propagation. An anisotropic metamagnetic transition was observed in the ordered state at 2 K in an applied magnetic field of 0.85-3 T. (57)Fe Mössbauer spectroscopy reveals mixed hyperfine interactions below the ordering temperature, with strong electric field gradients and complex noncollinear arrangement of the magnetic moments.