The 50 most-cited articles in Inorganic Chemistry, 2017

A series of two-dimensional (2D) hybrid organic–inorganic perovskite (HOIP) crystals, based on acene alkylamine cations (i.e., phenylmethylammonium (PMA), 2-phenylethylammonium (PEA), 1-(2-naphthyl)methanammonium (NMA), and 2-(2-naphthyl)ethanammonium (NEA)) and lead(II) halide (i.e., PbX 4 2–, X = Cl, Br, and I) frameworks, and their corresponding thin films were fabricated and examined for structure–property relationship. Several new or redetermined crystal structures are reported, including those for (NEA) 2 PbI 4, (NEA) 2 PbBr 4, (NMA) 2 PbBr 4, (PMA) 2 PbBr 4, and (PEA) 2 PbI 4 . Non-centrosymmetric structures from among these 2D HOIPs were confirmed by piezoresponse force microscopy—especially noteworthy is the structure of (PMA) 2 PbBr 4, which was previously reported as centrosymmetric. Examination of the impact of organic cation and inorganic layer choice on the exciton absorption/emission properties, among the set of compounds considered, reveals that perovskite layer distortion (i.e., Pb–I–Pb bond angle between adjacent PbI 6 octahedra) has a more global effect on the…

Isostructural Zn(II)/Cd(II) mixed ligand coordination polymers (CPs) {[M( IPA )( L )]} n ( CP1 and CP2 ) built from isophthalic acid (H 2 IPA ) and 3-pyridylcarboxaldehyde nicotinoylhydrazone ( L ) were prepared using versatile synthetic routes: viz., diffusion of precursor solutions, conventional reflux methods, and green mechanochemical (grinding) reactions. Both robust CPs synthesized by different routes were characterized by various analytical methods, and their thermal and chemical stability as well as the phase purity was established. Crystallographic studies revealed that CP1 and CP2 are isostructural frameworks and feature a double-lined two-dimensional network composed of Zn 2+ /Cd 2+ nodes connected through IPA and pillared by the Schiff base ligand L with a double-walled edge. The photoluminescent (PL) properties of CP1 and CP2 have been exploited as dual detection fluorosensors for hexavalent chromate anions (CrO 4 2– /Cr 2 O 7 2– ) and 2,4,6-trinitrophenol (TNP) because it was observed that the emission intensity of aqueous suspensions of CPs selectively quenches by…

A series of five unique d–f heteronuclear luminescent metal–organic frameworks (MOFs) in an entangled polyrotaxane array and the light-harvesting block homonuclear zinc compound have been isolated successfully and characterized. The series of isostructural polymers feature 3,4-connected (4.8 2 )(4.8 3 .9 2 )(6.8.9) 2 (6.9 2 )(8 3 ) topology and high stability, exhibiting diverse void spaces. By taking advantage of the isostructural MOFs 2 and 3, the intensities of red and green emissions can be modulated by adjusting the ratios of Eu III and Tb III ions correspondingly, and white-light emission can be generated by a combination of different doped Tb III and Eu III concentrations. The Tb–Zn-based framework {[Tb 3 Zn 6 (bipy 2 ) 2 (Hmimda) 7 (H 2 O) 3 ]·5H 2 O} n ( 3; H 3 mimda = 2-methyl-1- H -imidazole-4,5-dicarboxylic acid and bipy = 4,4′-bipyridine) can detect trace Mg II ion with relatively high sensitivity and selectivity. Dehydrated MOF 3a shows a remarkable emission quenching effect through the introduction of I 2 solids. Further investigation indicates that it exhibits turn…

A bifunctional robust and highly porous imidazolium-based ionic liquid decorated UiO-67 type MOF (UiO-67-IL, 1 ) was successfully constructed via solvothermal assembly of the imidazolium-based ligand and Zr(IV) ions. It exhibits a highly selective adsorption for CO 2 over CH 4 and N 2 . Furthermore, 1 herein can be used as a highly active heterogeneous catalyst for CO 2 cycloaddition with epoxides under atmospheric pressure with or without cocatalyst TBAB ( n -Bu 4 NBr).

Three photoluminescent zinc coordination polymers (CPs), {[Zn 2 (tpeb) 2 (2,5-tdc)(2,5-Htdc) 2 ]·2H 2 O} n ( 1 ), {[Zn 2 (tpeb) 2 (1,4-ndc)(1,4-Hndc) 2 ]·2.6H 2 O} n ( 2 ), and {[Zn 2 (tpeb) 2 (2,3-ndc) 2 ]·H 2 O} n ( 3 ) (tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc = 1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicarboxylic acid) were prepared from reactions of Zn(NO 3 ) 2 ·6H 2 O with tpeb and 2,5-H 2 tdc, 1,4-H 2 ndc, or 2,3-H 2 ndc under solvothermal conditions. Compound 1 has a two-dimensional (2D) grid-like network formed from bridging 1D [Zn(tpeb)] n chains via 2,5-tdc dianions. 2 and 3 possess similar one-dimensional (1D) double-chain structures derived from bridging the [Zn(tpeb)] n chains via pairs of 1,4-ndc or 2,3-ndc ligands. The solid-state, visible emission by 1 – 3 was quenched by Cr 3+, CrO 4 2–, and Cr 2 O 7 2– ions in water with detection limits by the most responsive complex 3 of 0.88 ppb for Cr 3+ and 2.623 ppb for Cr 2 O 7 2– (pH = 3) or 1.734 ppb for CrO 4 2– (pH = 12). These values are…

Abstract As main-group chemistry, in particular boron chemistry, has expanded and developed over the past 20 years, one reagent has risen to prominence as well. Tris(pentafluorophenyl)borane, B(C6F5)3 (commonly known as BCF), has demonstrated extensive applications in a wide variety of reactions, including borylation, hydrogenation, hydrosilylation, frustrated Lewis pair (FLP) chemistry, Lewis acid catalysis, and more. The high Lewis acidity of B(C6F5)3 is derived from the electronic effects of its three C6F5 rings, rendering it a versatile reagent for a great number of reactions. In addition, the steric bulk of these rings also allows it to function as the Lewis acid in a FLP, granting this reagent yet another synthetically useful application. However, as main-group chemistry continues to evolve as a field, new reagents are required that go beyond BCF, increasing not only the range of reactions available but also the breadth of compounds attainable. Great strides have already been made in order to accomplish this task, and this review will highlight modern advances in boron…

Highly efficient decontamination of heavily toxic Cr 2 O 7 2– from water remains a serious task for public health and ecosystem protection. An easily regenerative and reused sorbent with suitable porosity may address this task. Herein, a series of water-stable and ecofriendly metal–organic frameworks (MOFs) with large surface areas were assessed for their ability to adsorb and separate Cr 2 O 7 2– from aqueous solutions. Among these tested MOFs, NU-1000 shows an extraordinary capability to efficiently capture (within 3 min) Cr 2 O 7 2– with a sorption capacity of up to 76.8 mg/g, which is the largest one for the neutral MOF-based Cr 2 O 7 2– sorbents. NU-1000 also shows remarkable selectivity for Cr 2 O 7 2– capture and can effectively reduce the Cr(VI) concentration from 24 ppm to 60 ppb, which is below the acceptable limit for the drinking water standard (100 ppb by the U.S. Environmental Protection Agency). Moreover, this adsorbent can be easily regenerated by Soxhlet extraction with an acidic methanol solution (2.5 M HCl) and can be reused at least three times without a…

In this Communication, we report a high-efficiency electrocatalyst for electrochemical water oxidation based on an Fe-doped Ni 2 P nanosheet array on a conductive carbon cloth. This catalyst shows a low onset overpotential of 190 mV, and it demands overpotentials of only 215 and 235 mV to drive 50 and 100 mA cm –2, respectively, with high electrochemical durability. This work offers us an attractive earth-abundant 3D catalyst electrode in water-splitting devices toward the mass production of hydrogen fuels for applications.

A new luminescent Zn(II)-based metal–organic framework (MOF), [Zn 2 (TPOM)(NDC) 2 ]·3.5H 2 O (Zn-MOF; TPOM = tetrakis(4-pyridyloxymethylene)methane and H 2 ndc = 2,6-naphthalenedicarboxylic acid), was successfully synthesized by a hydrothermal reaction. The MOF exhibits excellent luminescence emission, and it can detect Fe(III) and Cr(VI) ions with high selectivity, well antiinterference performance, and short response time. In addition, Zn-MOF was selected as a parent coordination compound to encapsulate Eu 3+ cations to obtain a Eu 3+ -incorporated sample (Eu 3+ @Zn-MOF). Subsequently, we explored the potential application of Eu 3+ @Zn-MOF as a probe for the selective sensing of Fe(III) and Cr(VI) ions, and it revealed that we could differentiate Fe(III) and Cr(VI) ions by the combination Zn-MOF and Eu 3+ @Zn-MOF. More importantly, it represents the first example of MOF-based luminescent sensors which can detect and differentiate Fe(III) and Cr(VI) ions selectively. And the possible sensing mechanism was discussed in detail.

Decreasing Li/Ni disorder has been a challenging problem for layered oxide materials, where disorder seriously restricts their electrochemical performances for lithium-ion batteries (LIBs). Element doping is a great strategy that has been widely used to stabilize the structure of the cathode material of an LIB and improve its electrochemical performance. On the basis of the results of previous studies, we hypothesized that the element of Ca, which has a lower valence state and larger radius compared to Ni 2+, would be an ideal doping element to decrease the Li/Ni disorder of LiMO 2 materials and enhance their electrochemical performances. A Ni-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode material was selected as the bare material, which usually shows severe Li/Ni disorder and serious capacity attenuation at a high cutoff voltage. So, a series of Ca-doped LiNi 0.8(1– x ) Co 0.1 Mn 0.1 Ca 0.8 x O 2 ( x = 0–8%) samples were synthesized by a traditional solid-state method. As hypothesized, neutron diffraction showed that Ca-doped LiNi 0.8 Co 0.1 Mn 0.1 O 2 possessed a lower degree of Li/Ni…

The discovery of new materials and their efficient syntheses is a fundamental goal of chemistry. A related objective is to identify foundational and rational approaches to enhance the art of synthesis by combining the exquisite predictability of organic synthesis with the high yields of solid-state chemistry. In contrast to so-called solid-state methods, inorganic syntheses in liquid fluxes permit bond formation, framework assembly, and crystallization at lower temperatures because of facile diffusion and chemical reactions with and within the flux itself. The fluxes are bona fide solvents similar to conventional organic or aqueous solvents. Such reactions can produce a wide range of materials, often metastable, from oxides to intermetallics, but typically the formation mechanisms are poorly understood. This article discusses how one can design, perform, observe, understand, and engineer the formation of compounds from inorganic melts. The focus is also design concepts such as "dimensional reduction", "phase homologies", and "panoramic synthesis", and their broad applicability. When…

New inorganic nonlinear-optical (NLO) materials are necessary for solid-state lasers to generate coherent radiation in the ultraviolet (UV) and deep-UV regions. The purpose of this Viewpoint is to describe the chemical and physical requirements for such materials, as well as the current state of the field. In addition, the "birefringence challenge" is described and a flowchart is presented for characterizing new second-harmonic-generation materials. Finally, several new materials are suggested that may have UV and/or deep-UV NLO applications.

A variety of Eu 3+ -activated BaZrGe 3 O 9 phosphors was synthesized via solid-state reaction. The phase formation of BaZrGe 3 O 9:Eu 3+ samples was verified by powder X-ray diffraction analysis, while Rietveld refinement method was used to confirm the crystal structure. The electronic structure and characteristic photoluminescence as well as cathodoluminescence properties were researched in detail. The samples show strong absorption at 394 nm, which matches well with the commercial near-ultraviolet chips. Under 394 nm excitation, the phosphors exhibit the characteristic emissions of Eu 3+ ions consistent with the 5 D 0 – 7 F J transitions. Then we investigated the thermal stability detailedly. The temperature-dependent photoluminescence emission spectra suggest that the obtained phosphors have favorable thermal stability. A white light-emitting diode (WLED) lamp with low correlated color temperature and good color render index was fabricated with blue-emitting BaMgAl 10 O 17:Eu 2+, green-emitting Sr 2 SiO 4:Eu 2+ (commercial), and red-emitting BaZrGe 3 O 9:Eu 3+ phosphors in…

In this study, vanadium sesquioxide (V 2 O 3 ), dioxide (VO 2 ), and pentoxide (V 2 O 5 ) were all synthesized from a single polyol route through the precipitation of an intermediate precursor: vanadium ethylene glycolate (VEG). Various annealing treatments of the VEG precursor, under controlled atmosphere and temperature, led to the successful synthesis of the three pure oxides, with sub-micrometer crystallite size. To the best of our knowledge, the synthesis of the three oxides V 2 O 5, VO 2, and V 2 O 3 from a single polyol batch has never been reported in the literature. In a second part of the study, the potentialities brought about by the successful preparation of sub-micrometer V 2 O 5, VO 2, and V 2 O 3 are illustrated by the characterization of the electrochromic properties of V 2 O 5 films, a discussion about the metal to insulator transition of VO 2 on the basis of in situ measurements versus temperature of its electrical and optical properties, and the characterization of the magnetic transition of V 2 O 3 powder from SQUID measurements. For the latter compound, the…

Pulsed capacitors require high-recoverable energy-storage density ( W rec ) and high energy-storage efficiency (η), which can be realized through the selection and adjustment of the composition. In this work, (1 – x )SrTiO 3 – x (0.95Bi 0.5 Na 0.5 TiO 3 –0.05BaAl 0.5 Nb 0.5 O 3 ) [(1 – x )ST– x (BNT–BAN)] ceramics were successfully prepared via the pressureless solid-state reaction method. The dielectric constant increases gradually with the introduction of BNT–BAN and obtains a maximum value of 3430 with the composition of 0.4ST–0.6(BNT–BAN) at 100 Hz, which is 10.39 times higher than that of the pure ST sample (∼330). Dispersive relaxor behaviors and ferroelectric performances can be enhanced with the introduction of BNT–BAN. The composition of 0.5ST–0.5(BNT–BAN) exhibits a high W rec of 1.89 J/cm 3 as well as a high η of 77%. Therefore, the (1 – x )ST– x (BNT–BAN) systems are candidate materials for pulsed capacitor applications.

Abstract Three new water-stable luminescent Cd­(II) coordination polymers (CPs), {[Cd2(bptc)­(2,2′-bipy)2(H2O)2]}n (1), {[Cd2(bptc)­(phen)2]·4H2O}n (2), and {[Cd2(bptc)­(4,4′-bipy)­(H2O)2]·4H2O}n (3), were solvothermally synthesized with mixed ligands of 3,3′,5,5′-biphenyltetracarboxylic acid (H4bptc) and N-donor ligands (2,2′-bipy = 2,2′-bipyridine; phen = 1,10-phenanthroline; 4,4′-bipy = 4,4′-bipyridine). The CPs 1–3 show structural diversity from a 1D ladder chain to a 2D layer to a 3D porous framework, tuned by different ancillary ligands. Topological analyses reveal that the CP 2 is a 4-connected uninodal 2D net with the Schläfli point symbol {44·62}, while the CP 3 displays a 4,6-connected 2-nodal 3D net with the point symbol {3·42·52·6}­{32·42·52·64·74·8}. Luminescent property studies reveal that the CPs 1–3 are promising luminescent sensors that can highly select and sensitively detect ferric and chromate/dichromate ions, in which the CP 1 with a 1D structure showed the best performance, free from the interference of other ions present in an aqueous medium. Moreover, the…

A unique metal–organic complex (MOC) with formula [Eu 2 (tpbpc) 4 ·CO 3 ·4H 2 O]·DMF·solvent (Htpbpc = 4′-[4,2′;6′,4″]-terpyridin-4′-yl-biphenyl-4-carboxylic acid) has been successfully constructed under solvothermal conditions. The Eu complex, as proved by structural analysis, exhibits a fascinating 1D linear-type chain structure which is further extended to a 3D H-bonded supramolecular framework. The luminescent investigations confirm that the emission behavior of the Eu complex possesses excellent water stability and pH stability, and it is the first example of a MOC-based fluorescent probe with high selectivity, high sensitivity, and low detection limit, targeting Cr(III) and Cr(VI) (CrO 4 2– /Cr 2 O 7 2– ) ions in aqueous solution. Importantly, the luminescence can be fast and simple, regenerated in detecting CrO 4 2– and Cr 2 O 7 2– ions. Furthermore, the simple fluorescent-based test paper was successfully prepared and provided a reliable and visual detection of Cr 3+, CrO 4 2–, and Cr 2 O 7 2– ions in daily applications.

Zn(II)/Cd(II)-based dual ligand Luminescent Metal–Organic Frameworks (LMOFs) {[M( ATA )( L )]} n · x H 2 O ( 1 ) and ( 2 ) were synthesized by versatile synthetic routes, viz., diffusion of precursor solutions, conventional reflux, and green mechanochemical (grinding) reactions from bipyridyl-based Schiff base, ( E )- N ′-(pyridin-4-ylmethylene)isonicotinohydrazide ( L ) and amino functionalized 2-aminoterephthalic acid (H 2 ATA ) as linkers. Chemical and thermal stability, phase purity, and characterization of both LMOFs were established by various analytical methods. SXRD analysis revealed the 3D framework is composed of two-dimensional [M( ATA )] n nets doubly pillared by L through the terminal nitrogen atom. Selective and sensitive detection of chromate anions (CrO 4 2– /Cr 2 O 7 2– ) and Fe 3+ /Pd 2+ cations in the aqueous phase by fluorescent quenching of the LMOFs 1 and 2 has been established. Competitive experiments in the presence of interfering anions/cations with 1 and 2 revealed no major change in the quenching efficiency. The observed limits of detection (LOD) values by…

The temperature-dependent structure evolution of the hybrid halide perovskite compounds, formamidinium tin iodide (FASnI 3, FA + = CH[NH 2 ] 2 + ) and formamidinium lead bromide (FAPbBr 3 ), has been monitored using high-resolution synchrotron X-ray powder diffraction between 300 and 100 K. The data are consistent with a transition from cubic Pm 3 m (No. 221) to tetragonal P 4/ mbm (No. 127) for both materials upon cooling; this occurs for FAPbBr 3 between 275 and 250 K, and for FASnI 3 between 250 and 225 K. Upon further cooling, between 150 and 125 K, both materials undergo a transition to an orthorhombic Pnma (No. 62) structure. The transitions are confirmed by calorimetry and dielectric measurements. In the tetragonal regime, the coefficients of volumetric thermal expansion of FASnI 3 and FAPbBr 3 are among the highest recorded for any extended inorganic crystalline solid, reaching 219 ppm K –1 for FASnI 3 at 225 K. Atomic displacement parameters of all atoms for both materials suggest dynamic motion is occurring in the inorganic sublattice due to the flexibility of the…

Abstract In recent years, Zr-based metal–organic frameworks (MOFs) have been developed that facilitate catalytic degradation of toxic organophosphate agents, such as chemical warfare agents (CWAs). Because of strict regulations, experiments using live agents are not possible for most laboratories and, as a result, simulants are used in the majority of cases. Reports that employ real CWAs are scarce and do not cover the whole spectrum of agents. We here present a comparative study in which UiO-66-NH2, NU-1000, MOF-808, and PCN-777 are evaluated for their effectiveness in the degradation of paraoxon and the chemical warfare agents tabun, VX, and soman, in N-ethylmorpholine buffer (pH 10) as well as in pure water. All MOFs showed excellent ability to degrade the agents under basic conditions. It was further disclosed that tabun is degraded by different mechanisms depending on the conditions. The presence of an amine, either as part of the MOF structure (UiO-66-NH2) or in the agent itself (VX, tabun), is the most important factor governing degradation rates in water. The results show…

New porous anionic Ln-MOFs, namely, [Me 2 NH 2 ][Ln(CPA) 2 (H 2 O) 2 ] (Ln = Eu, Gd), have been prepared through the self-assembly of 5-(4-carboxy phenyl)picolinic acid (H 2 CPA) and lanthanide ions. They feature open anionic frameworks with 1-D hydrophilic channels and exchangeable dimethylamine ions. The Eu phase could detect Fe 3+ ions with high selectivity and sensitivity in either aqueous solution or biological condition. The ratios of lanthanide ions on this structure platform could be rationally tuned to not only achieve dichromatic emission colors with linear correlation but also attain three primary colors (RGB) and even white light with favorable correlated color temperature. Furthermore, the Ag(I)-exchanged phases can be readily reduced to afford Ag nanoparticles. The as-prepared Ag@Ln-MOFs composite shows highly efficient catalytic performance for the reduction of 4-nitrophenol.

In this study, we report the electrocatalytic behavior of the neutral, monomeric Cu(II) complex of diacetyl-bis( N -4-methyl-3-thiosemicarbazonato), CuL 1, for metal-assisted ligand-centered hydrogen evolution in acetonitrile and dimethylformamide. CuL 1 displays a maximum turnover frequency (TOF) of 10 000 s –1 in acetonitrile and 5100 s –1 in dimethylformamide at an overpotential of 0.80 and 0.76 V, respectively. The rate law is first-order in catalyst and second-order in proton concentration. Gas analysis from controlled potential electrolysis confirms CuL 1 as an electrocatalyst to produce H 2 with a minimum Faradaic efficiency of 81% and turnover numbers as high as 73 while showing no sign of degradation over 23 h. The H 2 evolution reaction (HER) was probed using deuterated acid, demonstrating a kinetic isotope effect of 7.54. A proton inventory study suggests one proton is involved in the rate-determining step. Catalytic intermediates were identified using 1 H NMR, X-ray photoelectron, and UV–visible spectroscopies. All catalytic intermediates in the proposed mechanism were…

Transition-metal (TM)-doped boron clusters have received considerable attention in recent years, in part, because of their remarkable size-dependent structural and electronic properties. However, the structures of medium-sized boron clusters doped with TM atoms are still not well-known because of the much increased complexity of the potential surface as well as the rapid increase in the number of low-energy isomers, which are the challenges in cluster structural searches. Here, by means of an unbiased structure search, we systematically investigated the structural evolution of medium-sized tantalum-doped boron clusters, TaB n 0/– ( n = 10–20). The results revealed that TaB n 0/– ( n = 10–15) clusters adopt half-sandwich molecular geometries, with the notable exception of TaB 10 –, while for n = 16–18 and 19–20, the lowest-energy clusters are characterized by drum-type geometries and tubular molecules with two B atoms on the top, respectively. Good agreement between the calculated and experimental photoelectron spectra strongly support the validity of our global minimum structures.…

Abstract Interest in hybrid organic–inorganic lead halide compounds with perovskite-like two-dimensional crystal structures is growing due to the unique electronic and optoelectronic properties of these compounds. Herein, we demonstrate the synthesis, thermal and optical properties, and calculations of the electronic band structures for one- and two-layer compounds comprising both cesium and guanidinium cations: Cs[C(NH2)3]PbI4 (I), Cs[C(NH2)3]PbBr4 (II), and Cs2[C(NH2)3]Pb2Br7 (III). Compounds I and II exhibit intense photoluminescence at low temperatures, whereas compound III is emissive at room temperature. All of the obtained substances are stable in air and do not thermally decompose until 300 °C. Since Cs+ and C(NH2)3+ are increasingly utilized in precursor solutions for depositing polycrystalline lead halide perovskite thin films for photovoltaics, exploring possible compounds within this compositional space is of high practical relevance to understanding the photophysics and atomistic chemical nature of such films.

Actinide chemistry is gaining increased focus in modern research, particularly in the fields of energy research and molecular magnetism. However, the structure-function and structure-property relationships of actinides have still not been studied as intensely as those for transition metals. In this work, we report a detailed ab initio study of the spectroscopic, magnetic, and bonding properties of the trivalent actinide free ions and their associated hexachloride complexes in octahedral symmetry. The electronic structures of these systems are examined using complete active-space self-consistent-field calculations followed by second-order N-electron valence perturbation theory, including both scalar relativistic and spin-orbit-coupling effects. The computed energies and wave functions are further analyzed by means of ab initio ligand-field theory (AILFT) and finally chemically interpreted by means of the angular overlap model (AOM). The derived Slater-Condon and spin-orbit parameters have allowed us to systematically rationalize the spectroscopic and magnetic properties of the…

A water-stable 3D luminescent metal–organic framework (MOF), [Eu 6 Zn(μ 3 -OH) 8 (NDC) 6 (H 2 O) 6 ] n ( 1 ), constructed from heterometallic [Eu III 6 Zn II ] clusters and electron-rich π-conjugated 1,4-naphthalenedicarboxylic acid (H 2 NDC) ligands exhibits highly sensitive, selective, and reversible detection of ronidazole, which represents the first example of luminescent MOFs based on Ln-TM heterometallic clusters for the detection of antibiotics in aqueous solution.

A trimethylamine (TEA)-assisted synthesis approach that combines the preparation of hierarchical porous zeolitic imidazolate framework ZIF-8 nanoparticles and one-pot encapsulation of target molecules is presented. Two dye molecules, rhodamine B (RhB) and methylene blue (MB), and one protein (bovine serum albumin, BSA) were tested as the target molecules. The addition of TEA into the solution of zinc nitrate promoted the formation of ZnO nanocrystals, which rapidly transformed to ZIF-8 nanoparticles after the addition of the linker 2-methylimidazole (Hmim). Hierarchical porous dye@ZIF-8 nanoparticles with high crystallinity, large BET surface areas (1300–2500 m 2 /g), and large pore volumes (0.5–1.0 cm 3 /g) could be synthesized. The synthesis procedure was fast (down to 2 min) and scalable. The Hmim/Zn ratio could be greatly reduced (down to 2:1) compared to previously reported ones. The surface areas, and the mesopore size, structure, and density could be modified by changing the TEA or dye concentrations, or by postsynthetic treatment using reflux in methanol. This synthesis and…

Abstract Despite decades of research, the structure–activity relationship of nitrogenase is still not understood. Only recently was the full molecular structure of the FeMo cofactor (FeMoco) revealed, but the charge and metal oxidation states of FeMoco have been controversial. With the recent identification of the interstitial atom as a carbide and the more recent revised oxidation-state assignment of the molybdenum atom as Mo(III), here we revisit the Mössbauer properties of FeMoco. By a detailed error analysis of density functional theory-computed isomer shifts and computing isomer shifts relative to the P-cluster, we find that only the charge of [MoFe7S9C]1– fits the experimental data. In view of the recent Mo(III) identification, the charge of [MoFe7S9C]1– corresponds to a formal oxidation-state assignment of Mo(III)3Fe(II)4Fe(III), although due to spin delocalization, the physical oxidation state distribution might also be interpreted as Mo(III)1Fe(II)4Fe(2.5)2Fe(III), according to a localized orbital analysis of the MS = 3/2 broken symmetry solution. These results can be…

Heavy-metal ions and nitroaromatic substances are highly toxic and harmful to human health and the ecological environment. It is an urgent issue to selectively detect and capture these toxic substances. By introducing the triazole ligand to the π-conjugated aromatic carboxylate system and borrowing the organic template open framework idea, a stable fluorescent framework [Me 2 NH 2 ] 4 [Zn 6 (qptc) 3 (trz) 4 ]·6H 2 O ( 1 ) (H 4 qptc = terphenyl-2,5,2′5′-tetracarboxylic acid, trz = 1,2,4-triazole) has been successfully synthesized, which features Zn 4 (trz) 2 chain-based 3D anionic structure with channels filled by [Me 2 NH 2 ] + cations. It is worth noting that the material exhibits selective adsorption and recyclable detection of heavy-metal Cr 3+ ion in aqueous solutions, which may be the synergy from the metal charge, bond ability of metal ions to carboxylate oxygen atom, and soft–hard acid–base properties. Furthermore, it can selectively sense of 2,4,6-trinitrophenol with a large quenching coefficient K sv of 2.08 × 10 6 M –1 .

Herein three novel cobalt metal–organic frameworks (Co-MOFs) with similar ingredients, [Co (bib )( o- bdc )] ∞ ( 1 ), [Co 2 ( bib ) 2 ( m- bdc ) 2 ] ∞ ( 2 ), and {[Co( bib )( p- bdc )(H 2 O)](H 2 O) 0.5 } ∞ ( 3 ), have been synthesized from the reaction of cobalt nitrate with 1,4-bis(imidazol-1-yl)benzene ( bib ) and structure-related aromatic acids (1,2-benzenedicarboxylic acid = o -bdc, 1,3-benzenedicarboxylic acid = m -bdc, and 1,4-benzenedicarboxylic acid = p -bdc ) by the solvothermal method. It is aimed to perform systematic research on the relationship among the conformation of benzoate acid, lattice dimension of Co-MOF, and pore diameter of MOF-derived carbon composite. Through the precursor strategy, Co-MOFs 1 – 3 have been utilized to synthesize porous cobalt@carbon nanotube composites ( Co@CNT s). After the in situ gas-sulfurization, secondary composites CoS 2 @CNT s were successfully obtained, which kept similar morphologies of corresponding Co@CNT s without destroying previous highly dispersed structures. Co-MOFs and two series of composites ( Co@CNT s and CoS 2 @CNT s)…

Inspired by the ongoing search for new superionic lithium thiophosphates for use in solid-state batteries, we present the synthesis and structural characterization of Li 2 P 2 S 6, a novel crystalline lithium thiophosphate. Whereas M 2 P 2 S 6 with the different alkaline elements (M = Na, K, Rb, Cs) is known, the lithium counterpart has not been reported yet. Herein, we present a combination of synchrotron pair distribution function analysis and neutron powder diffraction to elucidate the crystal structure and possible Li + diffusion pathways of Li 2 P 2 S 6 . Additionally, impedance spectroscopy is used to evaluate its ionic conductivity. We show that Li 2 P 2 S 6 possesses P 2 S 6 2– polyhedral units with edge-sharing PS 4 tetrahedra and only one-dimensional diffusion pathways with localized Li–Li pairs, leading to a low ionic conductivity for lithium.

A new Cu(II) complex of an asymmetrically dicondensed Schiff base (H 2 L = N -(2-hydroxyacetophenylidene)- N ′-salicylidene-1,3-propanediamine) derived from 1,3-propanediamine, salicylaldehyde, and o -hydroxyacetophenone has been synthesized. Using this complex, [CuL] ( 1 ), as a metalloligand, two new trinuclear Cu-Mn complexes, [(CuL) 2 Mn(N 3 )(H 2 O)](ClO 4 )·H 2 O ( 2 ) and [(CuL) 2 Mn(NCS) 2 ] ( 3 ), have been prepared. Single-crystal structural analyses reveal that complexes 2 and 3 both have the same bent trinuclear {(CuL) 2 Mn} 2+ structural unit in which two terminal bidentate square-planar (CuL) units are chelated to the central octahedral Mn(II) ion. This structural similarity is also evident from the variable-temperature magnetic susceptibility measurements, which suggest that compounds 2 and 3 are both antiferromagnetically coupled with comparable exchange coupling constants (−21.8 and −22.3 cm –1, respectively). The only difference between 2 and 3 lies in the coordination around the central Mn(II) ion; in 3, two SCN – groups are coordinated to the Mn(II), leaving a…

Abstract Iron porphyrins can act as potent electrocatalysts for CO2 functionalization. The catalytically active species has been proposed to be a formal Fe(0) porphyrin complex, [Fe(TPP)]2– (TPP = tetraphenylporphyrin), generated by two-electron reduction of [FeII(TPP)]. Our combined spectroscopic and computational investigations reveal that the reduction is ligand-centered and that [Fe(TPP)]2– is best formulated as an intermediate-spin Fe(II) center that is antiferromagnetically coupled to a porphyrin diradical anion, yielding an overall singlet ground state. As such, [Fe(TPP)]2– contains two readily accessible electrons, setting the stage for CO2 reduction.

Lanthanide-doped upconversion nanoparticles with a suitable surface coating are appealing for biomedical applications. Because high-quality upconversion nanoparticles are typically prepared in an organic solvent and passivated by hydrophobic oleate ligands, a convenient and reliable method for the surface modification of upconversion nanoparticles is thus highly desired to satisfy downstream biological investigations. In this work, we describe a facile and versatile strategy for displacing native oleate ligands on upconversion nanoparticles with a diversity of hydrophilic molecules. The ligand-exchange procedure involves the removal of original oleate ligands followed by the attachment of new ligands in a separate step. The successful coating of relevant ligands was confirmed by Fourier transform infrared spectroscopy, thermogravimetry analysis, and ζ-potential measurement. The surface-modified nanoparticles display high stability and good biocompatibility, as revealed by electron microscopy, photoluminescence spectroscopy, and cytotoxicity assessment. Our study demonstrates that…

Metal-Metal Bonds: From Fundamentals to ApplicationsT he year 2017 marks the 10th anniversary of the passing of Prof. F. Albert Cotton, who described the first metal-metal multiple bonds in 1964. 1 Cotton's contributions to our understanding of metal-metal bonds were undeniably monumental, but nobody could claim that this field has died with him.Quite the contrarythe past 10 years have seen a renewed interest in metal-metal bonds, especially from a growing cadre of younger scientists in the early stages of their careers.Bonds between metals continue to expand beyond quadruple to bond orders of 5 or 6. 2 Synthetic chemists have applied their creativity to design compounds featuring new subclasses of metal-metal bonds that have heretofore not been seen, be they bonds among the transition metals, main-group elements, or even the long-overlooked f-block elements.From experimental to spectroscopic to computational, the development of new tools to study the electronic structure of metal-metal-bonded compounds continues to enlighten our understanding of bonding.This evolving perspective…

We have applied in situ monitoring of mechanochemical reactions by high-energy synchrotron powder X-ray diffraction to study the role of liquid additives on the mechanochemical synthesis of the archetypal metal-organic framework (MOF) HKUST-1, which was one of the first and is still among the most widely investigated MOF materials to be synthesized by solvent-free procedures. It is shown here how the kinetics and mechanisms of the mechanochemical synthesis of HKUST-1 can be influenced by milling conditions and additives, yielding on occasion two new and previously undetected intermediate phases containing a mononuclear copper core, and that finally rearrange to form the HKUST-1 architecture. On the basis of in situ data, we were able to tune and direct the milling reactions toward the formation of these intermediates, which were isolated and characterized by spectroscopic and structural means and their magnetic properties compared to those of HKUST-1. The results have shown that despite the relatively large breadth of analysis available for such widely investigated materials as…

A mononuclear hexacoordinate Cu(II) complex shows a field induced slow magnetic relaxation that is not facilitated by an energy barrier to spin reversal due to the zero-field splitting. Two relaxation channels were found: the magnetic field strongly supports the low-frequency relaxation path with a relaxation time as long as τ = 0.8 s at T = 1.9 K and B = 1.5 T. The mechanism of the relaxation at low temperature involves the dominant Raman process for this S = 1/2 spin system along with a temperature-independent term belonging to a quantum tunneling.

Redox inactive Lewis acidic cations are thought to facilitate the reactivity of metalloenzymes and their synthetic analogues by tuning the redox potential and electronic structure of the redox active site. To explore and quantify this effect, we report the synthesis and characterization of a series of tetradentate Schiff base ligands appended with a crown-like cavity incorporating a series of alkali and alkaline earth Lewis acidic cations ( 1M, where M = Na +, K +, Ca 2+, Sr 2+, and Ba 2+ ) and their corresponding Co(II) complexes ( 2M ). Cyclic voltammetry of the 2M complexes revealed that the Co(II/I) redox potentials are 130 mV more positive for M = Na + and K + and 230–270 mV more positive for M = Ca 2+, Sr 2+, and Ba 2+ compared to Co(salen–OMe) (salen–OMe = N, N ′-bis(3-methoxysalicylidene)-1,2-diaminoethane), which lacks a proximal cation. The Co(II/I) redox potentials for the dicationic compounds also correlate with the ionic size and Lewis acidity of the alkaline metal. Electronic absorption and infrared spectra indicate that the Lewis acid cations have a minor effect on…

We demonstrated a high-yield and easily reproducible synthesis of a highly active oxygen evolution reaction (OER) catalyst, “the core-oxidized amorphous cobalt phosphide nanostructures”. The rational formation of such core-oxidized amorphous cobalt phosphide nanostructures was accomplished by homogenization, drying, and annealing of a cobalt(II) acetate and sodium hypophosphite mixture taken in the weight ratio of 1:10 in an open atmosphere. Electrocatalytic studies were carried out on the same mixture and in comparison with commercial catalysts, viz., Co 3 O 4 -Sigma, NiO-Sigma, and RuO 2 -Sigma, have shown that our catalyst is superior to all three commercial catalysts in terms of having very low overpotential (287 mV at 10 mA cm –2 ), lower Tafel slope (0.070 V dec –1 ), good stability upon constant potential electrolysis, and accelerated degradation tests along with a significantly higher mass activity of 300 A g –1 at an overpotential of 360 mV. The synergism between the amorphous Co x P y shell with the Co 3 O 4 core is attributed to the observed enhancement in the OER…

Triarylboranes have attracted significantly increasing research interest as a remarkable class of photoelectronic π-electron materials. Because of the presence of vacant p orbital on the B center, the boryl group is a very unique electron acceptor that exhibits not only electron-accepting ability through p-π* conjugation but also high Lewis acidity to coordinate with Lewis bases and steric bulk arising from the aryl substituent on the B center to get enough kinetic stability. Thus, the incorporation of a trivalent B element into π-conjugated systems is an efficient strategy to tune the electronic and stereo structures and thus the photoelectronic properties of π-electron systems. When an electron-donating group, such as amino, is present, triarylboranes would likely display intramolecular charge-transfer transitions. These kinds of molecules are often highly emissive. In addition, the geometry of the molecules has a great impact on the emission properties. In this Forum Article, we herein describe our recent progress on the charge-transfer emitting triarylborane π-electron systems…

The four new Ag(I) complexes Ag(phen)(P 2 -nCB) ( 1 ), Ag(idmp)(P 2 -nCB) ( 2 ), Ag(dmp)(P 2 -nCB) ( 3 ), and Ag(dbp)(P 2 -nCB) ( 4 ) with P 2 -nCB = bis(diphenylphosphine)- nido -carborane, phen = 1,10-phenanthroline, idmp = 4,7-dimethyl-1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, and dbp = 2,9-di- n -butyl-1,10-phenanthroline were designed to demonstrate how to develop Ag(I) complexes that exhibit highly efficient thermally activated delayed fluorescence (TADF). The substituents on the 1,10-phenanthroline ligand affect the photophysical properties strongly (i) electronically via influencing the radiative rate of the S 1 → S 0 transition and (ii) structurally by rigidifying the molecular geometry with respect to geometry changes occurring in the lowest excited S 1 and T 1 states. The oscillator strength of the S 1 ↔ S 0 transition f (S 1 ↔ S 0 )—an important parameter for the TADF efficiency being proportional to the radiative rate—can be increased from f (S 1 ↔ S 0 ) = 0.0258 for Ag(phen)(P 2 -nCB) ( 1 ) to f (S 1 ↔ S 0 ) = 0.0536 for Ag(dbp)(P 2 -nCB) ( 4 ), as…

Abstract We use a layered solution crystal growth method to synthesize high-quality single crystals of two different benzylammonium lead iodide perovskite-like organic/inorganic hybrids. The well-known (C6H5CH2NH3)2PbI4 phase is obtained in the form of bright orange platelets, with a structure comprised of single ⟨100⟩-terminated sheets of corner-sharing PbI6 octahedra separated by bilayers of the organic cations. The presence of water during synthesis leads to formation of a novel minority phase that crystallizes in the form of nearly transparent, light yellow bar-shaped crystals. This phase adopts the monoclinic space group P21/n and incorporates water molecules, with structural formula (C6H5CH2NH3)4Pb5I14·2H2O. The crystal structure consists of ribbons of edge-sharing PbI6 octahedra separated by the organic cations. Density functional theory calculations including spin–orbit coupling show that these edge-sharing PbI6 octahedra cause the band gap to increase with respect to corner-sharing PbI6 octahedra in (C6H5CH2NH3)2PbI4. To gain systematic insight, we model the effect of the…

A fundamental question concerning the chemical state of uranium in the binary oxides UO 2, U 4 O 9, U 3 O 7, U 3 O 8, and UO 3 is addressed. By utilizing high energy resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES) at the uranium M 4 edge, a novel technique in the tender X-ray region, we obtain the distribution of formal oxidation states in the mixed-valence oxides U 4 O 9, U 3 O 7, and U 3 O 8 . Moreover, we clearly identify a pivot from U(IV)–U(V) to U(V)–U(VI) charge compensation, corresponding with transition from a fluorite-type structure (U 3 O 7 ) to a layered structure (U 3 O 8 ). Such physicochemical properties are of interest to a broad audience of researchers and engineers active in domains ranging from fundamental physics to nuclear industry and environmental science.

Two multifunctional metal–organic frameworks based on cubane-like tetrahedron Tb 4 clusters as nodes have been synthesized and characterized. Compound 1 exhibits a 2D lanthanide–organic framework with Tb 4 clusters as nodes, and compound 2 possesses a 3D framework with Tb 4 clusters and Mn 2+ as nodes. Interestingly, luminescent investigations on them reveal that the two compounds can act as recyclable luminescent probes for chromium(VI) anion species and the corresponding detection limit can reach 10 –7 mol/L. Furthermore, 1 and 2 own efficient catalytic activity for the chemical fixation of CO 2 with epoxides under mild conditions. Importantly, they both can be recycled at least three times without compromising the activity.

We herein report the porous 4-fold interpenetrated mog (moganite) metal–organic framework (MOF) [Cd 3 (tipp)(bpdc) 2 ]·DMA·9H 2 O ( 1·Cd; H 2 tipp = 5,10,15,20-tetrakis(4-(imidazol-1-yl)phenyl)porphyrin, H 2 bpdc = biphenyl-4,4′-dicarboxylic acid, DMA = N, N ′-dimethylacetamide). The incorporation of Cd and carboxylate oxygen affords 1·Cd rich Lewis acid and basic sites. This MOF 1·Cd was then applied as an efficient heterogeneous catalyst for the important cyanosilylation of aldehydes and Knoevenagel condensation reactions. 1·Cd features excellent catalytic performance and recyclability for the cyanosilylation of various aldehydes with trimethylsilyl cyanide (TMSCN). Moreover, 1·Cd shows highly efficient catalysis and substrate selectivity for Knoevenagel condensation reactions of various aldehydes with malononitrile. The high catalytic activity and stability toward C–C bond formation make 1·Cd a promising heterogeneous catalyst.

Control of spin–lattice magnetic relaxation is crucial to observe long quantum coherence in spin systems at reasonable temperatures. Such a control is most often extremely difficult to achieve, because of the coexistence of several relaxation mechanisms, that is direct, Raman, and Orbach . These are not always easy to relate to the energy states of the investigated system, because of the contribution to the relaxation of additional spin-phonon coupling phenomena mediated by intramolecular vibrations. In this work, we have investigated the effect of slight changes on the molecular structure of four vanadium(IV)-based potential spin qubits on their spin dynamics, studied by alternate current (AC) susceptometry. The analysis of the magnetic field dependence of the relaxation time correlates well with the low-energy vibrational modes experimentally detected by time-domain THz spectroscopy. This confirms and extends our preliminary observations on the role played by spin-vibration coupling in determining the fine structure of the spin–lattice relaxation time as a function of the magnetic…

A novel blue-emitting Zn(II) MOF featuring parallel 2D+2D interpenetrated layers and tubelike channels was generated and shown to efficiently accommodate lanthanide(III) cations (Ln 3+ = Eu 3+, Tb 3+, or a mixture of Eu 3+ /Tb 3+ ), resulting in the Ln 3+ -encapsulated functional materials with a tunable emission color, including red, green, and nearly pure white light. Furthermore, the thermal-responsive luminescence was investigated for the lanthanide-codoped MOF to exhibit the chromic transition from white at room temperature to blue around liquid nitrogen temperature.

Four coordination polymers, namely, [Zn(HL1)(L2) 0.5 ]·H 2 O ( 1 ), [Cd(HL1)(L2) 0.5 ]·H 2 O ( 2 ), [Zn(L1)(L3) 0.5 ]·H 2 O ( 3 ), and [Cd(L1)(L3) 0.5 ] ( 4 ) (H 3 L1 = (3,5-dicarboxyl-phenyl)-(4-(2′-carboxyl-phenyl)-benzyl)ether, H 2 L2Cl 2 = 1,1′-bis(4-carboxy-benzyl)-4,4′-bipyridinium dichloride, and L3Cl 2 = 1,1′-dimethyl-4,4′-bipyridylium dichloride), have been synthesized hydrothermally. The structures of compounds 1 – 4 have been determined by single-crystal X-ray diffraction analyses, and further characterized by elemental analyses, infrared (IR) spectra, powder X-ray diffraction (PXRD) analyses, and thermogravimetric analyses. Compounds 1 and 2 display three-dimensional 2-fold interpenetrating frameworks, whereas compounds 3 and 4 exhibit two-dimensional layer structures. These compounds display photochromic behaviors from pale yellow to green under UV light, visible light, or sunlight. The photochromic mechanisms of these compounds have been studied by IR spectra, PXRD analyses, UV–vis absorption spectra, electron paramagnetic resonance spectra, density functional theory…

The synthesis and magnetic and theoretical studies of three isostructural heterometallic [Co III 2 Ln III 2 (μ 3 -OH) 2 ( o -tol) 4 (mdea) 2 (NO 3 ) 2 ] (Ln = Dy ( 1 ), Tb ( 2 ), Ho ( 3 )) “butterfly” complexes are reported ( o -tol = o -toluate, (mdea) 2– = doubly deprotonated N -methyldiethanolamine). The Co III ions are diamagnetic in these complexes. Analysis of the dc magnetic susceptibility measurements reveal antiferromagnetic exchange coupling between the two Ln III ions for all three complexes. ac magnetic susceptibility measurements reveal single-molecule magnet (SMM) behavior for complex 1, in the absence of an external magnetic field, with an anisotropy barrier U eff of 81.2 cm –1, while complexes 2 and 3 exhibit field induced SMM behavior, with a U eff value of 34.2 cm –1 for 2 . The barrier height for 3 could not be quantified. To understand the experimental observations, we performed DFT and ab initio CASSCF+RASSI-SO calculations to probe the single-ion properties and the nature and magnitude of the Ln III –Ln III magnetic coupling and to develop an understanding of…

The polyol route is a versatile and up-scalable method to produce large batches of iron oxide nanoparticles with well-defined structures and magnetic properties. Importance of parameters such as temperature and reaction time, heating profile, nature of the polyol solvent or organometallic precursors on nanostructure and properties has already been described in the literature. Yet, the crucial role of water in the forced hydrolysis pathway has never been reported, despite its mandatory presence for nanoparticle production. This communication investigates the influence of the water amount and temperature at which it is injected in the reflux system for either a pure polyol solvent system or a mixture with poly(hydroxy)amine. Distinct morphologies of nanoparticles were thereby obtained, from ultra-ultra-small smooth spheres down to 4 nm in diameter to larger ones up to 37 nm. Well-defined multicore assemblies with narrow grain size dispersity termed nanoflowers were also synthesized. A diverse and large library of samples was obtained by manipulating the nature of solvents and the…