Remodeling the Electronic Structure of Metallic Nickel and Ruthenium via Alloying in a Molecular Template for Sustainable Hydrogen Evolution.

The reasonably constructed high-performance electrocatalyst is crucial to achieve sustainable electrocatalytic water splitting. Alloying is a prospective approach to effectively boost the activity of metal electrocatalysts. However, it is a difficult subject for the controllable synthesis of small alloying nanostructures with high dispersion and robustness, preventing further application of alloy catalysts. Herein, we propose a well-defined molecular template to fabricate a highly dispersed NiRu alloy with ultrasmall size. The catalyst presents superior alkaline hydrogen evolution reaction (HER) performance featuring an overpotential as low as 20.6 ± 0.9 mV at 10 mA·cm-2. Particularly, it can work steadily for long periods of time at industrial-grade current densities of 0.5 and 1.0 A·cm-2 merely demanding low overpotentials of 65.7 ± 2.1 and 127.3 ± 4.3 mV, respectively. Spectral experiments and theoretical calculations revealed that alloying can change the d-band center of both Ni and Ru by remodeling the electron distribution and then optimizing the adsorption of intermediates to decrease the water dissociation energy barrier. Our research not only demonstrates the tremendous potential of molecular templates in architecting highly active ultrafine nanoalloy but also deepens the understanding of water electrolysis mechanism on alloy catalysts.

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects.

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

Multifunctional Dinuclear Dy-Based Coordination Complex Showing Visible Photoluminescence, Single-Molecule Magnet Behavior, and Proton Conduction.

A new Dy-based complex, [Dy2(phen)4(PAA)4](ClO4)2 (1), was obtained by using 4-hydroxyphenyl acetate (HPAA) as a ligand and 1,10-phenanthroline as an auxiliary ligand. Complex 1 shows a dinuclear structure and a 2D supramolecular layer constructed by π-π stacking interactions. The complex displays a characteristic Dy(III) emission. Moreover, magnetic susceptibility measurements revealed that 1 exhibits a single-molecule magnet (SMM) behavior. In addition, it also shows a proton conductivity of 1.08 × 10-5 S cm-1 under 353 K and 100% relative humidity conditions, which is mainly assigned to H-bonded networks formed by the undeprotonated and uncoordinated phenolic groups of HPAA ligands and guest water molecules. Remarkably, 1 is the first example of a dinuclear complex showing photoluminescence, SMM behavior, and proton conduction.

3-Pyridylacetic-Based Lanthanide Complexes Exhibiting Magnetic Entropy Changes, Single-Molecule Magnet, and Fluorescence.

Four complexes from lanthanides, 3-pyridylacetate, and 1,10-phenanthroline, formulated as [Ln2(3-PAA)2(µ-Cl)2(phen)4](ClO4)2 [Ln = Gd(1), Dy(2), Eu(3), Tb(4), 3-PAA = 3-pyridylacetic acid, phen = 1,10-phenanthroline], were obtained. The four compounds were characterized by IR spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. Compounds 1-4 are isomorphous, and they have a dinuclear structure. Magnetic studies reveal that 1 shows the magnetocaloric effect with -ΔS m max = 19.03 J kg-1 K-1 at 2 K for ΔH = 5 T, and 2 displays a field-induced single-molecule magnet with U eff = 19.02 K. The photoluminescent spectra of 3 and 4 exhibit strong characteristic emission, which demonstrate that the ligand-to-EuIII/TbIII energy transfer is efficient.

Anion Effects on Lanthanide(III) Tetrazole-1-acetate Dinuclear Complexes Showing Slow Magnetic Relaxation and Photofluorescent Emission.

Three types of lanthanide complexes based on the tetrazole-1-acetic acid ligand and the 2,2'-bipyridine coligand were prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analyses; the formulas of these complexes are [Ln2(1-tza)4(NO3)2(2,2'-bipy)2] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Dy2(1-tza)4Cl2(2,2'-bipy)2] (6), and [Yb2(1-tza)4(NO3)2(2,2'-bipy)2] (7) (1-tza = tetrazole-1-acetate and 2,2'-bipy = 2,2'-bipyridine). They are dinuclear complexes possessing similar structures but different lanthanide(III) ion coordination geometries because of the distinction of peripheral anions (such as NO3(-) and Cl(-)) and the effect of lanthanide contraction. The variable-temperature magnetic susceptibilities of 1-6 were measured. Both Dy(III) complexes (5 and 6) display field-induced single-molecule magnet behaviors. Ab initio calculations revealed that the Dy(III) complex 6 possesses a more anisotropic Dy(III) ion in comparison to that in 5. The room-temperature photoluminescence spectra of Sm(III) (1), Eu(III) (2), Tb(III) (4), and Dy(III) (5 and 6) complexes exhibit strong characteristic emissions in the visible region, whereas the Yb(III) (7) complex shows near-infrared (NIR) luminescence.

Poly[(µ(4)-5-bromo-pyridine-3-sulfonato)-silver(I)].

The silver(I) complex, [Ag(C(5)H(3)BrNO(3)S)](n), was obtained by reaction of AgNO(3) and 5-bromopyridine-3-sulfonic acid. The Ag(I) ion is coordinated by an O(3)N donor set in a slightly distorted tetra-hedral geometry. The Ag(I) ions are linked by µ(4)-5-bromo-pyridine-3-sulfonate ligands, forming a layer parallel to (100). The layers are further connected via C-H⋯Br hydrogen-bonding inter-actions into a three-dimensional supra-molecular network. The Ag⋯Ag separation is 3.0159 (6) Å, indicating the presence of argentophilic inter-actions.

Novel 3-D PtS-like tetrazolate-bridged manganese(II) complex exhibiting spin-canted antiferromagnetism and field-induced spin-flop transition.

Two novel manganese(II) tetrazolate coordination polymers, Mn 3(Hbta) 4(mu 2 -OH) 2(H 2O).2H 2O ( 1) and Mn(bta)(H 2O) ( 2), were obtained by the hydrothermal reaction of MnCl 2.4H 2O with N, N-bis[1(2) H-tetrazol-5-yl]amine (H 2bta) in different pH values. Compound 1 exhibits a 2-D (4,4) layer structure, which is built from binuclear Mn 2(mu 2-OH) 2 subunits and mu 3-bridging Hbta (-) linkers. Compound 2 is a helical framework, and its 3-D PtS-like net is constructed by Mn 2(bta) 2 dimers and mu 5-bridging bta (2-) linkers. Magnetic measurements reveal that compound 1 displays an antiferromagnetic ordering, while compound 2 exhibits the coexistence of a spin-canted antiferromagnetic coupling and a field-induced spin-flop transition.

Synthesis, crystal and band structures, and optical properties of a new mixed-framework mercury selenide diselenite, (Hg3Se2)(Se2O5).

A new mixed-framework mercury selenide diselenite, (Hg(3)Se(2))(Se(2)O(5)) (1), has been prepared by a solid-state reaction and structurally characterized by single-crystal X-ray diffraction analysis. The crystal structure of 1 consists of parallel stair-like cationic (Hg(3)Se(2))(2+) chains, which are bridged by (Se(2)O(5))(2-) anionic groups to form a novel 2-D layered mixed-framework. The optical properties were investigated in terms of the diffuse reflectance and microscopic infrared spectra. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that compound 1 is a semiconductor, and that the optical absorption of 1 is mainly ascribed to the charge transitions from the O-2p and Se(-II)-4p states to the Se(IV)-4p and Hg-6s states.

Synthesis, crystal and band structures, and properties of a new mixed three-dimensional framework metal pnictidehalide semiconductor, (Hg6Sb4)(CdI6).

A new, quaternary mercury and cadmium pnictidehalide semiconductor (Hg6Sb4)(CdI6) (1) has been prepared by the solid-state reaction and structurally characterized by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in the space group R-3c of the rhombohedral system with four formula units in a cell: a=13.3818(9) A, alpha=90.93 degrees, and V=2395.3(3) A3. The crystal structural novelty of 1 derives from the fact that a 3-D mercury antimonide cationic network interpenetrates with an unusual 3-D cadmium iodide octahedral anionic network through the weak covalent interactions between mercury and iodine atoms to form a mixed 3-D framework. Among them, the cationic moiety features a perovskite-like 3-D network while the anionic moiety is characterized by a 3-D I6 octahedral anionic network with two-thirds I6 octahedra being occupied by Cd atoms. The optical properties were investigated in terms of the diffuse reflectance and Fourier transform infrared spectra. The electronic band structure along with density of states calculated by the density functional theory method indicates that compound 1 is a semiconductor with a direct band gap and that the optical absorption of 1 is mainly ascribed to the charge transitions from I-5p and Sb-5p states to Cd-5s and Hg-6s states.