The development of a negative electrode for supercapacitors is a critical challenge for the next‐generation of energy‐storage devices. Herein, two new electrodes formed by the coordination polymers ...Ni(itmb)4(HPMo12O40)·2H2O (1) and Zn(itmb)3(H2O)(HPMo12O40)·4H2O (2) (itmb = 1‐(imidazo‐1‐ly)‐4‐(1,2,4‐triazol‐1‐ylmethyl)benzene), synthesized by a simple hydrothermal method, are described. Compounds 1 and 2 show high capacitances of 477.9 and 890.2 F g−1, respectively. An asymmetric supercapacitor device assembled using 2 which has novel water‐assisted proton channels as negative electrode and active carbon as positive electrode shows ultrahigh energy density and power density of 23.4 W h kg−1 and 3864.4 W kg−1, respectively. Moreover, the ability to feed a red light emitting diode (LED) also demonstrates the feasibility for practical use. The results allow a better elucidation of the storage mechanism in polyoxometalate‐based coordination polymers and provide a promising direction for exploring novel negative materials for new‐generation high‐performance supercapacitors.
Water‐assisted proton channels in a polyoxometalate polymer‐based asymmetric supercapacitor device is reported for boosting capacitance and achieving ultrahigh energy density. What's more, this work allows a better elucidation of the storage mechanism in polyoxometalate polymers and provides a promising direction for exploring novel negative materials for new‐generation supercapacitors.
A coordination polymer is fully exfoliated by solvent‐assisted interaction only. The soft‐delamination process results from the structure of the starting material, which shows a layered structure ...with weak layer‐to‐layer interactions and cavities with the ability to locate several solvents in an unselective way. These results represent a significant step forward towards the production of structurally designed one‐molecule thick 2D materials with tailored physico‐chemical properties.
We report the synthesis, magnetic properties, electrical conductivity, and delamination into thin nanosheets of two anilato-based Fe(II)/Fe(III) mixed-valence two-dimensional metal–organic ...frameworks (MOFs). Compounds (H3O)(H2O)(phenazine)3FeIIFeIII(C6O4X2)3·12H2O X = Cl (1) and Br (2) present a honeycomb layered structure with an eclipsed packing that generates hexagonal channels containing the water molecules. Both compounds show ferrimagnetic ordering at ca. 2 K coexisting with electrical conductivity (with room temperature conductivities of 0.03 and 0.003 S/cm). Changing the X group from Cl to Br leads to a decrease in the ordering temperature and room temperature conductivity that is correlated with the decrease of the electronegativity of X. Despite the ionic charge of the anilato-based layers, these MOFs can be easily delaminated in thin nanosheets with the thickness of a few monolayers.
We present a new example of a mononuclear iron(
ii
) complex exhibiting a correlated spin-crossover (SCO) transition and strong fluorescence, whose coordination sphere is saturated, for the first ...time, by six phosphorescent ligands. The interplay between SCO and light emission properties in the thermal region of the spin transition was investigated by means of magnetic, fluorescence, optical absorption and optical microscopy measurements on a single crystal. Overall, the results show an excellent correlation between fluorescence and magnetic data of the present gradual transition, indicating an extreme sensitivity of the optical activity of the ligand to the spin state of the active iron(
ii
) ions. These results open the way for conceiving new prototypes of pressure and temperature sensors based on this synergy between SCO and luminescence properties. In particular, the fact that cooperative SCO material is not a prerequisite for obtaining such synergetic effects, is useful for the design of thin films or nanoparticles, in which the cooperativity is reduced, for appropriate implementation in nanosized devices to enhance the sensing properties at the nanoscale.
Multifunctional mononuclear iron(
ii
) complex coordinated with six phosphorescent ligands exhibiting correlated spin-crossover transition and enhanced fluorescence.
We have prepared and characterized three coordination polymers formulated as Dy2(C6O4Cl2)3(fma)6 ⋅ 4.5fma (1) and Dy2(C6O4X2)3(fma)6 ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and ...C6O4X22−=3,6‐disubstituted‐2,5‐dihydroxy‐1,4‐benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)‐gon two‐dimensional hexagonal honey‐comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1–3 represent the first examples of anilato‐based lattices with formamide and field‐induced slow relaxation of the magnetization.
The anilato‐based DyIII‐containing compounds formulated as Dy2(C6O4Cl2)3(fma)6 ⋅ 4.5fma (1) and Dy2(C6O4X2)3(fma)6 ⋅ 4fma ⋅ 2H2O, with X=Br (2) and Cl (3), prepared with formamide as coordinating solvent, are coordination polymers with a honey‐comb layered structure showing slow magnetic relaxation when a DC field is applied. Compounds 1 and 3 are solvates obtained with a slow and fast crystallization method, respectively. Compounds 2 and 3 are isostructural.
Four difluorenoheteroles having a central quinoidal core with the heteroring varying as furan, thiophene, its dioxide derivative and pyrrole have shown to be medium character diradicals. Solid‐state ...structures, optical, photophysical, magnetic, and electrochemical properties have been discussed in terms of diradical character, variation of aromatic character and captodative effects (electron affinity). Organic field‐effect transistors (OFETs) have been prepared, showing balanced hole and electron mobilities of the order of 10−3 cm2 V−1 s−1 or ambipolar charge transport which is first inferred from their redox amphoterism. Quantum chemical calculations show that the electrical behavior is originated from the medium diradical character which produces similar reorganization energies for hole and electron transports. The vision of a diradical as simultaneously bearing pseudo‐hole and pseudo‐electron defects might justify the reduced values of reorganization energies for both regimes. Structure‐function relationships between diradical and ambipolar electrical behavior are revealed.
Diradicals are electrically ambipolar owing to the semiaperture of the π‐electron shell which produces redox amphoteric behaviour and small reorganization energies for hole and electron transports.
Precise design and construction of catalysts with satisfied performance for ambient electrolytic nitrogen reduction reaction (e‐NRR) is extremely challenging. By in situ integrating an electron‐rich ...polyoxometalates (POMs) into stable metal organic frameworks (MOFs), five POMs‐based MOFs formulated as FexCoy(Pbpy)9(ox)6(H2O)6P2W18O62·3H2O (abbreviated as FexCoyMOF‐P2W18) are created and directly used as catalysts for e‐NRR. Their electrocatalytic performances are remarkably improved thanks to complementary advantages and promising possibilities of MOFs and POMs. In particular, NH3 yield rates of 47.04 µg h−1 mgcat.−1 and Faradaic efficiency of 31.56% by FeCoMOF‐P2W18 for e‐NRR are significantly enhanced by a factor of 4 and 3, respectively, compared to the Fe0.5Co0.5(Pbpy)(ox)2·(Pbpy)0.5. The cyclic voltammetry curves, density functional theory calculations and in situ Fourier‐transform infrared spectroscopy confirm that there is a directional electron channel from P2W18 to the MOFs unit to accelerate the transfer of electrons. And the introduction of bimetals Fe and Co in the P2W18‐based MOFs can reduce the energy of the *N2 to *N2H step, thereby increasing the production of NH3. More importantly, this POM in situ embedding strategy can be extended to create other e‐NRR catalysts with enhanced performances, which opens a new avenue for future NH3 production for breakthrough in the bottleneck of e‐NRR.
Five polyoxometalate‐based metal‐organic frameworks (POMOFs) crystal materials based on {P2W18O62}6‐ with different Fe/Co ratios are precisely designed and synthesized by a simple hydrothermal method, which own the directional electron transfer from P2W18 to FexCoy‐MOFs. Especially, Fe1Co1‐P2W18 shows more excellent NH3 yield rate (47.04 µg h–1 mgcat.–1), FE (31.76 %) and long electrocatalytic stability compared other FexCoy‐P2W18.
Two novel polyoxometalate (POM)-encapsulated metal–organic nanotube (MONT) framework crystalline materials with unprecedented copper-mixed ligands, HUST-200 and HUST-201, have been successfully ...synthesized by an effective synthesis strategy. The encapsulation not only provides a shield to increase the chemical stability, but also does not affect its catalytic activity, and, therefore, the crystalline materials are very active for HER (H+ can diffuse easily through the pores of the MONTs). Remarkably, HUST-200 displays a low overpotential of 131 mV (catalytic current density is equal to 10 mA·cm–2). This work thus offers a new way for devising HER electrocatalysts with low cost using POM-encapsulated MONT frameworks.
Inclusion of quinoidal cores in conjugated hydrocarbons is a common strategy to modulate the properties of diradicaloids formed by aromaticity recovery within the quinoidal unit. Here we describe an ...alternative approach of tuning of diradical properties in indenoindenodibenzothiophenes upon anti → syn isomerism of the benzothiophene motif. This alters the relationship of the S atom with the radical center from linear to cross conjugation yet retains the same 2,6-naphtho conjugation pattern of the rearomatized core. We conduct a full comparison between the anti and syn derivatives based on structural, spectroscopic, theoretical, and magnetic measurements, showing that these systems are stable open-shell singlet diradicaloids that only access their triplet state at elevated temperatures.
A simple change of the substituents in the bridging ligand allows tuning of the ordering temperatures, T c, in the new family of layered chiral magnets AMIIMIII(X2An)3·G (A = (H3O)(phz)3+ (phz = ...phenazine) or NBu4 +; X2An2– = C6O4X2 2– = 2,5-dihydroxy-1,4-benzoquinone derivative dianion, with MIII = Cr, Fe; MII = Mn, Fe, Co, etc.; X = Cl, Br, I, H; G = water or acetone). Depending on the nature of X, an increase in T c from ca. 5.5 to 6.3, 8.2, and 11.0 K (for X = Cl, Br, I, and H, respectively) is observed in the MnCr derivative. Furthermore, the presence of the chiral cation (H3O)(phz)3+, formed by the association of a hydronium ion with three phenazine molecules, leads to a chiral structure where the Δ-(H3O)(phz)3+ cations are always located below the Δ-Cr(Cl2An)33– centers, leading to a very unusual localization of both kinds of metals (Cr and Mn) and to an eclipsed disposition of the layers. This eclipsed disposition generates hexagonal channels with a void volume of ca. 20% where guest molecules (acetone and water) can be reversibly absorbed. Here we present the structural and magnetic characterization of this new family of anilato-based molecular magnets.
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