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The development of a facile and reliable assay for arsenic (As) detection is crucial for its pollution control, which is a well-known heavy-metal pollutant in the environment. In this work, an efficient colorimetric method was established for As(V) detection based on a novel cuboid-shape Mn-Urea nanozyme (UMnzyme) with arsenic-enhanced oxidase-like activity. The UMnzyme was prepared through the coordination of Mn ions and carbonyl groups in urea, which possesses outstanding oxidase-like activity that can generate the superoxide anion free radical (O2˙−) by catalyzing the dissolved O2, triggering the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction. Furthermore, the free oxygen atoms in UMnzyme provide potential sites to bind with As, in which the formation of As–O will not destroy the morphology and structure of UMnzyme. The capture of As by UMnzyme results in the improvement of its oxidase-like activity; therefore, a colorimetric method for As(V) detection was developed with a linear range of 12.5–250 μg L−1. The limit of detection was determined to be 2.4 μg L−1 (S/N = 3), which is lower than the threshold (10 ppb) recommended by the World Health Organization. Moreover, the developed method was applied in the detection of As(V) in environmental water, and the recoveries are 89.5–103.6%. In short, this study provides an efficient and reliable strategy for As(V) detection based on a novel Mn-based nanozyme and a new idea for the reasonable design of Mn-based nanozymes with enhanced catalytic performance. [ABSTRACT FROM AUTHOR]

The synthesis, single-crystal structures and magnetic properties of two new double-zigzag-chain cyano-bridged heterobimetallic {[MII(Py-NOH)2][FeIII(Tp*)(CN)3]2}·H2O ([Fe III2 MII]) (Py–NOH = 4-pyridinealdoxime, Tp* = tris(3,5-dimethylpyrazol-1-yl)borohydride, M = Ni (1), Fe (2)) compounds are reported. The crystal structures of both compounds were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are isostructural, with the crystal structure comprising neutral double-zigzag (4,2-ribbon-like) bimetallic chains. The FeIII ion is coordinated by three cyanide carbon atoms and three nitrogen atoms of Tp* anions. However, the MII ion is surrounded by four cyanide nitrogen atoms and two nitrogen atoms from two Py-NOH ligands. The crystal structures and magnetic studies demonstrate that both complexes behave as single-chain magnetics (SCMs) with intrachain ferromagnetic coupling. Furthermore, [Fe III2 NiII] exhibits an excellent coercive field of 0.42 T at 1.8 K, among cyano-bridged 3d transition-metal-based SCMs reported thus far. Preliminary theoretical calculations provide a deep understanding of the magnetic properties of [Fe III2 NiII]. [ABSTRACT FROM AUTHOR]

Light-responsive adsorbents have attractive application prospects owing to their adjustable performance under light irradiation. Introducing light-responsive azobenzene moieties to a metal–organic framework (MOF) as the backbone of the organic linkers is a significant method to construct light-responsive adsorbents. The modulation of this kind of adsorbent via light irradiation requires maintaining exposure to the illumination with a specific wavelength. Herein, we report a series of light-responsive composites which realize the long-term suppressed bending of light-responsive ligands in the frameworks through short-time light irradiation. An inorganic persistent luminescent material, LiYGeO4:Bi3+, was incorporated into a light-responsive MOF, PCN-250, to fabricate the composites. After ultraviolet irradiation at 254 nm for 10 min, the LiYGeO4:Bi3+ in the composites can provide continuous illumination at 365 nm for at least 6 h. Driven by this illumination, the composites can regulate CO2 adsorption capacity without continuous light irradiation, and the best change amount of the adsorption capacity is up to 14.6%, while that on PCN-250 can be negligible. This work provides a new route to develop light-responsive materials for real-world applications. [ABSTRACT FROM AUTHOR]

γ-Valerolactone (GVL) is an important lignocellulosic platform molecule with huge potential for various industrial and chemical applications, which is usually produced using levulinic acid (LA) or its esters as raw materials. However, a two-step reaction process in which hydrogenation of the carbonyl groups on metal sites and subsequent lactonization catalyzed by acidic sites over multiple catalysts has generally been needed to realize this synthesis. In this work, a hierarchically multifunctional single catalyst of Ru/phosphotungstic acid/hierarchically porous UiO-66 (Ru/HPW/HP-UiO-66), simultaneously integrated with acidic and metal sites, has been fabricated via a simple strategy and successfully applied in the one-pot synthesis of GVL using methyl levulinate (ML) as the raw material. The hierarchically porous and nanosized (∼15 nm) HP-UiO-66 can not only provide sufficient space for the mass transfer of substrates but also favors the loading of bulk HPW molecules, which can effectively mediate the catalytic activities and stability of Ru NPs using the confined pore effect of UiO-66 and the strong interaction between HPW and Ru. When applied in the one-pot synthesis of GVL, the hierarchical Ru/HPW/HP-UiO-66 catalyst showed excellent catalytic activity (>97% yield) and stability (maintained after 7 successive cycles) for GVL. More importantly, the hierarchical catalyst also exhibited an extraordinary performance in the hydrogenation of different unsaturated hydrocarbons in aqueous solution. It is expected that our study offers a novel route to biomass upgrades involving metal/acid bifunctional synergistic catalysts. [ABSTRACT FROM AUTHOR]

The novel multidentate chelating ligands N′-(2-pyridylmethylidene)-2-(2-pyridylmethylideneamino)benzohydrazide (Hpphz) and N′-(2-salicylmethylidene)-2-(2-salicylmethylideneamino)benzohydrazide (H3sshz), which incorporate both amine and acylhydrazine Schiff base groups, were synthesized and investigated in DyIII coordination chemistry. The reactions of Hpphz and Dy(OAc)3·4H2O have yielded two {Dy2} featuring double OAc− bridges: [Dy2(H2aphz)2(OAc)4(ROH)2] [R = Me (1) and Et (2)], where the Hpphz ligands were in situ hydrolyzed into 2-amino-(2-pyridylmethylideneamino)benzohydrazide ions (H2aphz−). Besides, the reaction between H3sshz and Dy(NO)3·6H2O afforded a [Dy6(sshz)4(μ3-OH)4(μ4-O)(MeOH)4]2·17.5MeOH·2H2O cluster (3). This cluster contained two discrete {Dy6} cores, each of which consisted of a pair of {Dy3} triangular units. All the complexes displayed a single relaxation process of single-molecule magnet (SMM) behaviors under a zero dc field. Both 1 and 2 showed field-induced dual magnetic-relaxation behaviors. However, their diluted samples (1@Y and 2@Y) only showed one-step relaxation behaviors whether under a zero or applied dc field, indicating that the dual magnetic-relaxation behaviors of 1 and 2 were absent after the dilution. Combined with ab initio calculations, it could be infered that the dual magnetic-relaxation behaviors of 1 and 2 might be ascribled to the joint contributions of the single ion anisotropy and magnetic interactions. Examples of this type are rather rare in previous studies. Ab initio calculations also suggested that the discrepancy between the relaxation processes of 1 and 2 may be caused by the small difference between their magnetic interactions. [ABSTRACT FROM AUTHOR]

Complete active space self-consistent field (CASSCF) combined with restricted active space spin interaction with spin–orbit coupling (RASSI-SO) was used to probe why single-ion magnets (SIMs) composed of the "prolate" lanthanide ion ErIII cannot possess huge energy barriers. According to the proposal by Long et al., equatorially coordinated ligand environments are preferable for "prolate" lanthanide ions to have large energy barriers. However, our calculations show that the larger gx,y values in the first excited Kramers' doublets (KDs) induced by the surrounding equatorially coordinated ligands lead to their larger transversal magnetic moments which result in fast quantum tunneling of magnetizations (QTMs) in their first excited states. Therefore, the spin-phonon transitions can only proceed from the ground to the first excited KDs for our studied three compounds and all models. However, the effective energy barriers Ueff of the three compounds are smaller than the calculated energy gaps between the lowest two KDs due to their more flexible molecular structures. For the above reason, the energy barriers did not increase continuously as we expected when we decreased the Er–L bond lengths. We deduced that mononuclear ErIII compounds cannot easily possess huge energy barriers through enhancing the surrounding equatorially coordinated ligand field. [ABSTRACT FROM AUTHOR]

The reaction of Dy(NO3)3·6H2O and an asymmetric Schiff-base linker 5-chloro-2-(((2-hydroxy-3-methoxybenzyl)imino)methyl) phenol (H2L) afforded a dinuclear compound [Dy2L2(HL)(NO3)(EtOH)]·0.5C2H5OH (1). Complex 1 features two inequivalent Dy(III) sites, where three ligand sets (one HL− moiety and two L2− groups) are shared by two Dy(III) ions. The strategic introduction of CH3COOH in the reaction system used for synthesizing 1 induces the replacement of the HL− ligand by the CH3COO− ion, consequently resulting in the generation of [Et3NH][Dy2L2(NO3)(CH3COO)2] (2). In complex 2, two Dy(III) centers adopt NO7 (D2d geometry) and NO6 (C2v) coordination sphere, respectively. DC magnetic susceptibility studies for the two complexes indicate ferromagnetic interactions. Complexes 1 and 2 exhibit single-molecule magnet behavior with two-step slow relaxation processes due to the possession of inequivalent metal sites. The energy barriers of 69.19 and 45.73 K for 1, and 92.77 and 72.95 K for 2 are determined. Theoretical calculations reveal that the two-step relaxation processes in both 1 and 2 mainly originate from the single-ion magnetism of two distinct Dy(III) ions with inequivalent coordination environments. [ABSTRACT FROM AUTHOR]

A class of cyano-bridged 3d–4f zig-zag chain compounds, {RE[TM(CN)6] (PNO)2(H2O)4}·(H2O) {RE = YIII, TM = [FeIII]LS (1); RE = DyIII, TM = [FeIII]LS (2), CoIII (3)}, have been synthesized and characterized by single-crystal X-ray diffraction. The rare earth ions in these compounds are situated in a slightly distorted triangular dodecahedral (D2d) coordination environment. The magnetic properties of compounds 1–3 have been comparatively studied in detail. Under a zero dc field, the temperature dependence of ac susceptibility measurements for YFe (1) indicates the absence of magnetic relaxation stemming from the single anisotropic [FeIII]LS ion. The dysprosium analogue DyFe (2) shows only magnetic relaxation behavior with a prominent QTM effect, while DyCo (3) exhibits SIM properties not completely covered by QTM, with an extracted energy barrier of 73 K under a zero dc field. The ab initio calculations indicate that both compounds 2 and 3 are SMMs with well-behaved magnetic relaxation properties primarily from the individual DyIII ion. Therefore, the different magnetic behaviors exhibited by compound 2 compared to 3 may be ascribed to the stronger QTM effect caused by the extra weak interaction of [FeIII]LS ions in 2 as a fluctuating transverse field around the DyIII ion. The QTM effect for both 2 and 3 is suppressed under an applied dc field with an effective energy barrier of 134 and 150 K, respectively. Compared with compound 2, the higher extracted Ueff/kB and χ′′(T) peak temperature for 3 should be further attributed to its slightly higher single-ion axiality as calculated and the elimination of the transverse field from the [FeIII]LS ion. [ABSTRACT FROM AUTHOR]

Here we present a facile aqueous approach to synthesize heterostructured CdSe/CdS QDs with all-inorganic chalcogenide S2− ligands under mild conditions. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and steady-state emission spectroscopy demonstrate that the heterostructured CdSe/CdS QDs with sulfur-rich surface composition are formed by heterogeneous nucleation of Cd2+ and S2− precursors on the CdSe QDs. After adsorption of small Ni(OH)2 clusters over the surface in situ, the CdSe/CdS–Ni(OH)2 photocatalyst enables H2 production efficiently with an internal quantum yield of 52% under visible light irradiation at 455 nm, up to an 8-fold increase of activity to that of spherical CdSe QDs–Ni(OH)2 under the same conditions. Femtosecond transient absorption spectroscopy, X-ray transient absorption (XTA) spectroscopy, steady-state and time-resolved emission spectroscopy show that the quasi-type-II band alignment in the CdSe/CdS heterostructure is responsible for the efficiency enhancement of light harvesting and surface/interfacial charge separation in solar energy conversion. The unprecedented results exemplify an easily accessible pattern of aqueous synthesis of all-inorganic heterostructured QDs for advanced photosynthetic H2 evolution. [ABSTRACT FROM AUTHOR]

The synthesis, single-crystal structures and magnetic properties of two new double-zigzag-chain cyano-bridged heterobimetallic {[M II (Py-NOH) 2 ][Fe III (Tp*)(CN) 3 ] 2 }·H 2 O ([FeIII2M II ]) (Py-NOH = 4-pyridinealdoxime, Tp* = tris(3,5-dimethylpyrazol-1-yl)borohydride, M = Ni (1), Fe (2)) compounds are reported. The crystal structures of both compounds were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are isostructural, with the crystal structure comprising neutral double-zigzag (4,2-ribbon-like) bimetallic chains. The Fe III ion is coordinated by three cyanide carbon atoms and three nitrogen atoms of Tp* anions. However, the M II ion is surrounded by four cyanide nitrogen atoms and two nitrogen atoms from two Py-NOH ligands. The crystal structures and magnetic studies demonstrate that both complexes behave as single-chain magnetics (SCMs) with intrachain ferromagnetic coupling. Furthermore, [FeIII2Ni II ] exhibits an excellent coercive field of 0.42 T at 1.8 K, among cyano-bridged 3d transition-metal-based SCMs reported thus far. Preliminary theoretical calculations provide a deep understanding of the magnetic properties of [FeIII2Ni II ].

Complete active space self-consistent field (CASSCF) combined with restricted active space spin interaction with spin-orbit coupling (RASSI-SO) was used to probe why single-ion magnets (SIMs) composed of the "prolate" lanthanide ion ErIII cannot possess huge energy barriers. According to the proposal by Long et al., equatorially coordinated ligand environments are preferable for "prolate" lanthanide ions to have large energy barriers. However, our calculations show that the larger gx,y values in the first excited Kramers' doublets (KDs) induced by the surrounding equatorially coordinated ligands lead to their larger transversal magnetic moments which result in fast quantum tunneling of magnetizations (QTMs) in their first excited states. Therefore, the spin-phonon transitions can only proceed from the ground to the first excited KDs for our studied three compounds and all models. However, the effective energy barriers Ueff of the three compounds are smaller than the calculated energy gaps between the lowest two KDs due to their more flexible molecular structures. For the above reason, the energy barriers did not increase continuously as we expected when we decreased the Er-L bond lengths. We deduced that mononuclear ErIII compounds cannot easily possess huge energy barriers through enhancing the surrounding equatorially coordinated ligand field.

The reaction of Dy(NO3)3·6H2O and an asymmetric Schiff-base linker 5-chloro-2-(((2-hydroxy-3-methoxybenzyl)imino)methyl) phenol (H2L) afforded a dinuclear compound [Dy2L2(HL)(NO3)(EtOH)]·0.5C2H5OH (1). Complex 1 features two inequivalent Dy(iii) sites, where three ligand sets (one HL- moiety and two L2- groups) are shared by two Dy(iii) ions. The strategic introduction of CH3COOH in the reaction system used for synthesizing 1 induces the replacement of the HL- ligand by the CH3COO- ion, consequently resulting in the generation of [Et3NH][Dy2L2(NO3)(CH3COO)2] (2). In complex 2, two Dy(iii) centers adopt NO7 (D2d geometry) and NO6 (C2v) coordination sphere, respectively. DC magnetic susceptibility studies for the two complexes indicate ferromagnetic interactions. Complexes 1 and 2 exhibit single-molecule magnet behavior with two-step slow relaxation processes due to the possession of inequivalent metal sites. The energy barriers of 69.19 and 45.73 K for 1, and 92.77 and 72.95 K for 2 are determined. Theoretical calculations reveal that the two-step relaxation processes in both 1 and 2 mainly originate from the single-ion magnetism of two distinct Dy(iii) ions with inequivalent coordination environments.

A class of cyano-bridged 3d-4f zig-zag chain compounds, {RE[TM(CN) 6 ] (PNO) 2 (H 2 O) 4 }·(H 2 O) {RE = Y III , TM = [Fe III ] LS (1); RE = Dy III , TM = [Fe III ] LS (2), Co III (3)}, have been synthesized and characterized by single-crystal X-ray diffraction. The rare earth ions in these compounds are situated in a slightly distorted triangular dodecahedral (D 2d ) coordination environment. The magnetic properties of compounds 1-3 have been comparatively studied in detail. Under a zero dc field, the temperature dependence of ac susceptibility measurements for YFe (1) indicates the absence of magnetic relaxation stemming from the single anisotropic [Fe III ] LS ion. The dysprosium analogue DyFe (2) shows only magnetic relaxation behavior with a prominent QTM effect, while DyCo (3) exhibits SIM properties not completely covered by QTM, with an extracted energy barrier of 73 K under a zero dc field. The ab initio calculations indicate that both compounds 2 and 3 are SMMs with well-behaved magnetic relaxation properties primarily from the individual Dy III ion. Therefore, the different magnetic behaviors exhibited by compound 2 compared to 3 may be ascribed to the stronger QTM effect caused by the extra weak interaction of [Fe III ] LS ions in 2 as a fluctuating transverse field around the Dy III ion. The QTM effect for both 2 and 3 is suppressed under an applied dc field with an effective energy barrier of 134 and 150 K, respectively. Compared with compound 2, the higher extracted U eff /k B and χ''(T) peak temperature for 3 should be further attributed to its slightly higher single-ion axiality as calculated and the elimination of the transverse field from the [Fe III ] LS ion.