Understanding the microcrystal tests of three related phenethylamines: the ortho‐metallated (±)‐amphetamine formed with gold(III) chloride,and the tetrachloridoaurate(III) salts of (+)‐methamphetamine and (±)‐ephedrine

The ortho‐metallation product of the reaction of (±)‐amphetamine with gold(III) chloride, [D,L‐2‐(2‐aminopropyl)phenyl‐κ²N,C¹]dichloridogold(III), [Au(C₉H₁₂N)Cl₂], and the two salts resulting from crystallization of (+)‐methamphetamine with gold(III) chloride, D‐methyl(1‐phenylpropan‐2‐yl)azanium tetrachloridoaurate(III), (C₁₀H₁₆N)[AuCl₄], and of (±)‐ephedrine with gold(III) chloride, D,L‐(1‐hydroxy‐1‐phenylpropan‐2‐yl)(methyl)azanium tetrachloridoaurate(III), (C₁₀H₁₆NO)[AuCl₄], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six‐membered ring structure; the second and third each form a salt with [AuCl₄]⁻ (each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.     

Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex

Improving our comprehension of diverse CO₂ activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO₂ activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO₂ is readily reduced to CO, but isolated thorium(III) CO₂ activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)₃] ( 1 , Cp′′={C₅H₃(SiMe₃)₂‐1,3}), reacts with CO₂ to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′)₂[κ²‐O₂C{C₅H₃‐3,3′‐(SiMe₃)₂}]}₂(μ‐κ²:κ²‐C₂O₄)] ( 3 ). The concomitant formation of oxalate and carboxylate is unique for CO₂ activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO₂ activation can differ from better understood uranium(III) chemistry.     

Synthesis of Boron(III)‐Coordinated Subchlorophins and Their Peripheral Modifications

A pyrrole‐cleaving modification to transform boron(III) meso ‐triphenylsubporphyrin into boron(III) meso ‐triphenylsubchlorophin has been developed. Boron(III) subchlorophins thus synthesized show absorption and fluorescence spectra that are roughly similar to those of boron(III) subchlorins, but B ‐methoxy boron(III) subchlorophin showed considerably intensified fluorescence and a small Stokes shift. Peripheral modification reactions of B ‐phenyl boron(III) subchlorophin such as regioselective nitration with Cu(NO₃)₂⋅3 H₂O, ipso ‐substitution reactions of boron(III) α‐nitrosubchlorophin with CsF and CsCl, and Pd‐catalyzed cross‐coupling reactions of boron(III) α‐chlorosubchlorophin with arylacetylenes, have been also explored to tune the optical properties of subchlorophins.     

Enhancement of Anodic Response for DMSO at Ruthenium Oxide Film Electrodes as a Result of Doping with Iron(III)

The oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO₂) is representative of numerous anodic oxygen‐transfer reactions of organosulfur compounds that suffer from slow kinetics at noble metal electrodes. Anodic voltammetric data for DMSO are examined at various RuO₂‐film electrodes prepared by thermal deposition on titanium substrates. The response for DMSO is slightly larger at RuO₂ films prepared in a flame as compared with films prepared in a furnace; however, temperature is more easily controlled in the furnace. Doping of the RuO₂ films with Fe(III) further improves the sensitivity of anodic response for DMSO. Optimal response is obtained at an Fe(III)‐doped RuO₂‐film electrode prepared using a deposition solution of 50 mM RuCl₃ and 10 mM FeCl₃ in a 1 : 1 mixture of isopropanol and 12 M HCl at an annealing temperature of 450 °C. The Levich plot (i vs. ω^1/2) and Koutecky‐Levich plot (1/i vs. 1/ω^1/2) of amperometric data for the oxidation of DMSO at an Fe(III)‐doped RuO₂‐film electrode configured as a rotated disk are consistent with an anodic response controlled by mass‐transport processes at low rotational velocities. Flow injection data demonstrate that Fe(III)‐doped RuO₂‐film electrodes exhibit detection capability for methionine and cysteine in addition to DMSO. Detection limits for 100‐μL injections of the three compounds are ca. 3.2×10^?4 mM, i.e., ca. 32 pmol.     

A five‐coordinate iron(III) porphyrin complex including a neutral axial pyridine N‐oxide ligand

While six‐coordinate iron(III) porphyrin complexes with pyridine N‐oxides as axial ligands have been studied as they exhibit rare spin‐crossover behavior, studies of five‐coordinate iron(III) porphyrin complexes including neutral axial ligands are rare. A five‐coordinate pyridine N‐oxide–5,10,15,20‐tetraphenylporphyrinate–iron(III) complex, namely (pyridine N‐oxide‐κO)(5,10,15,20‐tetraphenylporphinato‐κ⁴N,N′,N′′,N′′′)iron(III) hexafluoroantimonate(V) dichloromethane disolvate, [Fe(C₄₄H₂₈N₄)(C₅H₅NO)][SbF₆]·2CH₂Cl₂, was isolated and its crystal structure determined in the space group P. The porphyrin core is moderately saddled and the Fe—O—N bond angle is 122.08 (13)°. The average Fe—N bond length is 2.03 Å and the Fe—ONC₅H₅ bond length is 1.9500 (14) Å. This complex provides a rare example of a five‐coordinate iron(III) porphyrin complex that is coordinated to a neutral organic ligand through an O‐monodentate binding mode.     

Crystallographic identification of a series of manganese porphyrin complexes with nitrogenous bases

Studying the axial ligation behavior of metalloporphyrins with nitrogenous bases helps to better understand not only the biological function of heme‐based protein systems, but also the catalytic properties of porphyrin‐based reaction sites in other biomimetic synthetic support environments. Unlike iron porphyrin complexes, little is known about the axial ligation behavior of Mn porphyrins, particularly in the solid state with Mn in the +3 oxidation state. Here, we present the syntheses and crystal and molecular structures of three new high‐spin manganese(III) porphyrin complexes with the different amine‐based axial ligands imidazole (im), piperidine (pip), and 1,4‐diazabicyclo[2.2.2]octane (DABCO), namely bis(imidazole)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride chloroform disolvate, [Mn(C₄₄H₂₈N₄)(C₃H₄N₂)₂]Cl·2CHCl₃ or [Mn(TPP)(im)₂]Cl·2CHCl₃ (TPP = 5,10,15,20‐tetraphenylporphyrin), (I), bis(piperidine)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride, [Mn(C₄₄H₂₈N₄)(C₅H₁₁N)₂]Cl or [Mn(TPP)(pip)₂]Cl, (II), and chlorido(1,4‐diazabicyclo[2.2.2]octane)(5,10,15,20‐tetraphenylporphyrin)manganese(III)–1,4‐diazabicyclo[2.2.2]octane–toluene–water (4/4/4/1), [Mn(C₄₄H₂₈N₄)Cl(C₆H₁₂N₂)]·C₆H₁₂N₂·C₇H₈·0.25H₂O or [Mn(TPP)Cl(DABCO)]·(DABCO)·(toluene)·0.25H₂O, (IV). A fourth complex, chlorido(pyridine)(5,10,15,20‐tetraphenylporphryinato)manganese(III) pyridine disolvate, [Mn(C₄₄H₂₈N₄)Cl(C₅H₅N)]·2C₅H₅N or [Mn(TPP)Cl(py)]·2(py), (III), acquired using different crystallization methods from published data, is also reported and compared to the previous structures.     

Synthesis,Characterization, and Reactivity of Cobalt(III)–Oxygen Complexes Bearing a Macrocyclic N‐Tetramethylated Cyclam Ligand

Mononuclear metal–dioxygen species are key intermediates that are frequently observed in the catalytic cycles of dioxygen activation by metalloenzymes and their biomimetic compounds. In this work, a side‐on cobalt(III)–peroxo complex bearing a macrocyclic N‐tetramethylated cyclam (TMC) ligand, [Co^III(15‐TMC)(O₂)]⁺, was synthesized and characterized with various spectroscopic methods. Upon protonation, this cobalt(III)–peroxo complex was cleanly converted into an end‐on cobalt(III)–hydroperoxo complex, [Co^III(15‐TMC)(OOH)]²⁺. The cobalt(III)–hydroperoxo complex was further converted to [Co^III(15‐TMC‐CH₂‐O)]²⁺ by hydroxylation of a methyl group of the 15‐TMC ligand. Kinetic studies and ¹⁸O‐labeling experiments proposed that the aliphatic hydroxylation occurred via a Co^IV–oxo (or Co^III–oxyl) species, which was formed by O? O bond homolysis of the cobalt(III)–hydroperoxo complex. In conclusion, we have shown the synthesis, structural and spectroscopic characterization, and reactivities of mononuclear cobalt complexes with peroxo, hydroperoxo, and oxo ligands.     

Synthesis,Structure, and Magnetic Studies of a New Wheel‐Shaped [LiMnIII6] Cluster

The synthesis, crystal structure, and magnetic properties of a new hexanuclear manganese(III) complex are reported. The complex [LiMn₆(L)₆]OH · 2MeCN · 4MeOH · 1.5H₂O (LiH₂L = lithium 2‐{[bis(2‐hydroxyethyl)amino]methyl}‐4‐methylphenate) ( 1 ), was obtained from the reaction of one equivalent of LiH₂L with Mn(OAc)₂ in MeCN/MeOH (v:v/1:1). Single‐crystal X‐ray diffraction shows that six octahedrally coordinated manganese(III) ions define a ring and are linked by twelve bridging oxygen atoms from alkoxo groups. The resulting [Mn₆(OCH₂)₁₂] skeleton has the remarkable property of acting as a host for a octahedrally coordinated lithium ion in the center of the ring. Variable‐temperature solid‐state magnetic susceptibility studies of 1 in the temperature range 2.0–300 K reveal that the complex has a S = 12 ground state spin, showing ferromagnetic exchange interactions between the constituent manganese(III) ions.     

Preparation of a Yb(III)‐Incorporated porous polymer by post‐Coordination: Enhancement of gas adsorption and catalytic activity

We synthesized a Yb(III)‐incorporated microporous polymer (Yb‐ADA) and studied its gas adsorption property and catalytic activity. The adamantane‐based porous polymer (ADA) was obtained from an ethynyl‐functionalized adamantane derivative and 2,5‐dibromoterephthalic acid through Sonogashira–Hagihara cross‐coupling. ADA had two carboxyl groups which were used for Yb(III) coordination under basic conditions. The Brunauer‐Emmett‐Teller (BET) surface area of ADA was 970 m² g^?1. As Yb(III) ions were incorporated into ADA, the surface area of the polymer (Yb‐ADA) was reduced to 885 m² g^?1. However, Yb‐ADA exhibited a significantly enhanced CO₂ adsorption capacity despite the reduction of surface area. The CO₂ uptakes of ADA and Yb‐ADA were 1.56 and 2.36 mmol g^?1 at 298 K, respectively. The H₂ uptake of ADA also increased after coordination with Yb(III) from 1.15 to 1.40 wt % at 77 K. Yb‐ADA showed high catalytic activity in the acetalization of 4‐bromobenzaldehyde and furfural with trimethyl orthoformate and could be reused after recovery without severe loss of activity. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5291–5297     

Tricoordinate Organochromium(III) Complexes Supported by a Bulky Silylamido Ligand Produce Ultra‐High‐Molecular Weight Polyethylene in the Absence of Activators

Low‐coordinate organoCr(III) complexes supported by the silylamido ligand –N(SiMe₃)DIPP (DIPP = 2,6‐diisopropylphenyl) are ethylene polymerization catalyst precursors without the need of additional cocatalyst. The reaction of CrCl₃(THF)₃ with 3 or 2 equiv. of LiN(SiMe₃)DIPP yields either a four‐membered cyclometalated Cr complex or Cr[N(SiMe₃)DIPP]₂Cl, respectively, with no trace of Cr[N(SiMe₃)DIPP]₃. Addition of 1 equiv. of LiN(SiMe₃)DIPP to Cr[N(SiMe₃)DIPP]₂Cl also leads to the four‐membered metallacycle, which upon heating transforms to a new six‐membered Cr metallacycle, likely via a σ‐bond metathesis step. Cr[N(SiMe₃)DIPP]₂Cl can be readily converted to bis(amido)Cr(III) vinyl and alkyl complexes Cr[N(SiMe₃)DIPP]₂R (R = vinyl, Bn, and Me). All of these structurally characterized low‐coordinate Cr(III) complexes with a Cr–C bond initiate the polymerization of ethylene in the absence of activators or cocatalysts, producing ultra‐high‐molecular weight polyethylene.     

meso‐Nitro‐ and meso‐Aminosubporphyrinatoboron(III)s and meso‐to‐meso Azosubporphyrinatoboron(III)s

meso‐Nitrosubporphyrinatoboron(III) was synthesized by nitration of meso‐free subporphyrin with AgNO₂/I₂. The subsequent reduction with a combination of NaBH₄ and Pd/C gave meso‐aminosubporphyrinatoboron(III). meso‐Nitro‐ and meso‐amino‐groups significantly influenced the electronic properties of subporphyrin, which has been confirmed by NMR and UV/Vis spectra, electrochemical analysis, and DFT calculations. Oxidation of meso‐aminosubporphyrinatoboron(III)s with PbO₂ cleanly gave meso‐to‐meso azosubporphyrinatoboron(III)s that exhibited almost coplanar conformations and large electronic interaction through the azo‐bridge.     

Aqueous solution and solid state interactions of lanthanide ions with a methacrylic ester polymer bearing pendant 15‐crown‐5 moieties

The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H₂O and D₂O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M^?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H₂O and D₂O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M^?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007     

Lanthanide(III) Complexes of 4,10‐Bis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid (trans‐H6do2a2p) in Solution and in the Solid State: Structural Studies Along the Series

Complexes of 4,10‐bis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid (trans‐H₆do2a2p, H₆ L ) with transition metal and lanthanide(III) ions were investigated. The stability constant values of the divalent and trivalent metal‐ion complexes are between the corresponding values of H₄dota and H₈dotp complexes, as a consequence of the ligand basicity. The solid‐state structures of the ligand and of nine lanthanide(III) complexes were determined by X‐ray diffraction. All the complexes are present as twisted‐square‐antiprismatic isomers and their structures can be divided into two series. The first one involves nona‐coordinated complexes of the large lanthanide(III) ions (Ce, Nd, Sm) with a coordinated water molecule. In the series of Sm, Eu, Tb, Dy, Er, Yb, the complexes are octa‐coordinated only by the ligand donor atoms and their coordination cages are more irregular. The formation kinetics and the acid‐assisted dissociation of several Ln^III–H₆ L complexes were investigated at different temperatures and compared with analogous data for complexes of other dota‐like ligands. The [Ce( L )(H₂O)]^3? complex is the most kinetically inert among complexes of the investigated lanthanide(III) ions (Ce, Eu, Gd, Yb). Among mixed phosphonate–acetate dota analogues, kinetic inertness of the cerium(III) complexes is increased with a higher number of phosphonate arms in the ligand, whereas the opposite is true for europium(III) complexes. According to the ¹H NMR spectroscopic pseudo‐contact shifts for the Ce–Eu and Tb–Yb series, the solution structures of the complexes reflect the structures of the [Ce(H L )(H₂O)]^2? and [Yb(H L )]^2? anions, respectively, found in the solid state. However, these solution NMR spectroscopic studies showed that there is no unambiguous relation between ³¹P/¹H lanthanide‐induced shift (LIS) values and coordination of water in the complexes; the values rather express a relative position of the central ions between the N₄ and O₄ planes.     

Separation of Iron(III) with Ammonium Thiocyanate‐H2O‐n‐Propyl Alcohol Extraction System in the Presence of Sodium Chloride

The behavior and conditions of liquid‐liquid extraction‐separation of Fe(III) by ammonium thiocyanate‐H₂O‐n‐propyl alcohol system in the presence of NaCl were studied, and the possible reactive mechanism of extraction of Fe(III) was deduced. The study showed that, in the presence of a given amount of NaCl, phases were separated thoroughly between n‐propyl alcohol and water. In the process of phase separation, the complex [Fe(SCN)_n]^(3‐n) formed by NH₄SCN and Fe(III) was quantitatively extracted into the n‐propyl alcohol phase. The extracted Fe(III) exists in the n‐propyl alcohol phase mainly as the forms of Fe(SCN)₂⁺ and Fe(SCN)₃. Also, the relationship between extraction yield of Fe(III) and the amount of NH₄SCN agreed well with the quadratic equation E = 0.54 + 58.14x ? 8.39x² (E and x represent the recovery rate of Fe(III) and the volume (mL) of 0.1 M NH₄SCN respectively). The quadratic R‐Square is 0.9990. With this method, Fe(III) can be completely separated from Co(II), Ni(II), Mn(II), Al(III), Bi(III) and Cd(II) at pH 1.0?2.0. The present method was applied in determining Fe(III) in samples with satisfactory results such as relative standard deviation from 2.06% to 2.89% and recovery rate in the range of 98.4?101.4%.     

Synthesis,Crystal Structure,and Magnetic Property of New Trispin Ln(III)‐Nitronyl Nitroxide Complexes

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)₃[NITPh(MeO)₂]₂} (Ln = Eu( 1 ), Gd( 2 ), Tb( 3 ), Dy( 4 ); NITPh(MeO)₂ = 2‐(3′,4′‐dimethoxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide; hfac = hexafluoroacetylacetonate). The single‐crystal X‐ray diffraction analysis shows that these complexes have similar mononuclear trispin structures, in which central Ln(III) ion is eight‐coordinated by two O‐atoms from two nitroxide groups and six O‐atoms from three hfac anions. The variable temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (J_Gd‐Rad = 3.40 cm^?1, J_Rad‐Rad = ?9.99 cm^?1) in complex 2 . Meanwhile, antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4 , and ferromagnetic interaction between Tb(III) and radicals in complex 3 , respectively.     

Three new phosphoric triamides with a [C(O)NH]P(O)[N(C)(C)]2 skeleton: a database analysis of C—N—C and P—N—C bond angles

In N,N,N′,N′‐tetraethyl‐N′′‐(4‐fluorobenzoyl)phosphoric triamide, C₁₅H₂₅FN₃O₂P, (I), and N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis(4‐methylpiperidin‐1‐yl)phosphoric triamide, C₁₉H₂₈F₂N₃O₂P, (II), the C—N—C angle at each tertiary N atom is significantly smaller than the two P—N—C angles. For the other new structure, N,N′‐dicyclohexyl‐N′′‐(2‐fluorobenzoyl)‐N,N′‐dimethylphosphoric triamide, C₂₁H₃₃FN₃O₂P, (III), one C—N—C angle [117.08 (12)°] has a greater value than the related P—N—C angle [115.59 (9)°] at the same N atom. Furthermore, for most of the analogous structures with a [C(=O)NH]P(=O)[N(C)(C)]₂ skeleton deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388], the C—N—C angle is significantly smaller than the two P—N—C angles; exceptions were found for four structures with the N‐methylcyclohexylamide substituent, similar to (III), one structure with the seven‐membered cyclic amide azepan‐1‐yl substituent and one structure with an N‐methylbenzylamide substituent. The asymmetric units of (I), (II) and (III) contain one molecule, and in the crystal structures, adjacent molecules are linked via pairs of N—H...O=P hydrogen bonds to form dimers.     

Fe (III)‐grafted Bi2MoO6 nanoplates for enhanced photocatalytic activities on tetracycline degradation and HMF oxidation

Fe (III)‐grafted Bi₂MoO₆ nanoplates (Fe (III)/BMO) with varying small quantity of Fe (III) clusters modification were fabricated through a simple hydrothermal and impregnation process. The characterization results indicate that the modification of Fe (III) clusters on the surface of Bi₂MoO₆ nanoplates with intimate interfacial contact is beneficial to the expansion of visible light absorption range and the separation of photoinduced carriers during the interface charge transfer process. The photocatalytic properties of the samples were studied by degradation of tetracycline (TC) and selective aerobic oxidation of biomass‐derived chemical 5‐hydroxymethylfuraldehyde (HMF) under visible light. The 1.5 wt% Fe (III) clusters‐grafted Bi₂MoO₆ nanoplates exhibited optimum photocatalytic activity, which is the TC degradation kinetic rate constant is 5.3 times higher than that of bare BMO, and the highest HMF conversion of 32.62% can be obtained with a selectivity of 95.30%. Furthermore, a possible visible light photocatalysis mechanism over Fe (III)/BMO sample has been proposed. This study may supply some insight for the development of visible‐light‐driven Bi₂MoO₆‐based photocatalysts applicable to both environmental remediation and biomass‐derived chemical transformation.     

Production of 5‐Hydroxymethylfurfural from Fructose in Ionic Liquid Efficiently Catalyzed by Cr(III)‐Al2O3 Catalyst

A series of metal‐Al₂O₃ catalysts were prepared simply by the conventional impregnation with Al₂O₃ and metal chlorides, which were applied to the dehydration of fructose to 5‐hydroxymethylfurfural (HMF). An agreeable HMF yield of 93.1% was achieved from fructose at mild conditions (100°C and 40 min) when employing Cr(III)‐Al₂O₃ as catalyst in 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl). The Cr(III)‐Al₂O₃ catalyst was characterized via XRD, DRS and Raman spectra and the results clarified the interaction between the Cr(III) and the alumina support. Meanwhile, the reaction solvents ([Bmim]Cl) collected after 1^st reaction run and 5^th reaction run were analyzed by ICP‐OES and LC‐ITMS and the results confirmed that no Cr(III) ion was dropped off from the alumina support during the fructose dehydration. Notably, Cr(III)‐Al₂O₃ catalyst had an excellent catalytic performance for glucose and sucrose and the HMF yields were reached to 73.7% and 84.1% at 120°C for 60 min, respectively. Furthermore, the system of Cr(III)‐Al₂O₃ and [Bmim]Cl exhibited a constant stability and activity at 100°C for 40 min and a favorable HMF yield was maintained after ten recycles.     

Hydrated hexacyanometallate(III) salts of triaqua(18‐crown‐6)lanthanoid(III) and tetraaqua(18‐crown‐6)lanthanoid(III) cations containing nine‐ and ten‐coordinate lanthanoids

Tetraaqua(18‐crown‐6)cerium(III) hexacyanoferrate(III) dihydrate, [Ce(C₁₂H₂₄O₆)(H₂O)₄][Fe(CN)₆]·2H₂O, and tetraaqua(18‐crown‐6)neodymium(III) hexacyanoferrate(III) dihydrate, [Nd(C₁₂H₂₄O₆)(H₂O)₄][Fe(CN)₆]·2H₂O, are isomorphous and isostructural in the C2/c space group, where the cations, which contain ten‐coordinate lanthanoid centres, lie across twofold rotation axes and the anions lie across inversion centres. In these compounds, an extensive series of O—H...O and O—H...N hydrogen bonds links the components into a continuous three‐dimensional framework. Triaqua(18‐crown‐6)lanthanoid(III) hexacyanoferrate(III) dihydrate, [Ln(C₁₂H₂₄O₆)(H₂O)₃][Fe(CN)₆]·2H₂O, where Ln = Sm, Eu, Gd or Tb, are all isomorphous and isostructural in the P space group, as are triaqua(18‐crown‐6)gadolinium(III) hexacyanochromate(III) dihydrate, [Gd(C₁₂H₂₄O₆)(H₂O)₃][Cr(CN)₆]·2H₂O, and triaqua(18‐crown‐6)gadolinium(III) hexacyanocobaltate(III) dihydrate, [Gd(C₁₂H₂₄O₆)(H₂O)₃][Co(CN)₆]·2H₂O. In these compounds, there are two independent anions, both lying across inversion centres, and the lanthanoid centres exhibit nine‐coordination; in the crystal structures, an extensive series of hydrogen bonds links the components into a three‐dimensional framework.     

Slow Magnetic Relaxation from Hard‐Axis Metal Ions in Tetranuclear Single‐Molecule Magnets

We report the synthesis of the novel heterometallic complex [Fe₃Cr(L)₂(dpm)₆]?Et₂O ( Fe₃CrPh ) (Hdpm=dipivaloylmethane, H₃L=2‐hydroxymethyl‐2‐phenylpropane‐1,3‐diol), obtained by replacing the central iron(III) atom by a chromium(III) ion in an Fe₄ propeller‐like single‐molecule magnet (SMM). Structural and analytical data, high‐frequency EPR (HF‐EPR) and magnetic studies indicate that the compound is a solid solution of chromium‐centred Fe₃Cr (S=6) and Fe₄ (S=5) species in an 84:16 ratio. Although SMM behaviour is retained, the |D| parameter is considerably reduced as compared with the corresponding tetra‐iron(III) propeller (D=?0.179 vs. ?0.418 cm^?1), and results in a lower energy barrier for magnetisation reversal (U_eff/k_B=7.0 vs. 15.6 K). The origin of magnetic anisotropy in Fe₃CrPh has been fully elucidated by preparing its Cr‐ and Fe‐doped Ga₄ analogues, which contain chromium(III) in the central position (c) and iron(III) in two magnetically distinct peripheral sites (p1 and p2). According to HF‐EPR spectra, the Cr and Fe dopants have hard‐axis anisotropies with D_c=0.470(5) cm^?1, E_c=0.029(1) cm^?1, D_p1=0.710(5) cm^?1, E_p1=0.077(3) cm^?1, D_p2=0.602(5) cm^?1, and E_p2=0.101(3) cm^?1. Inspection of projection coefficients shows that contributions from dipolar interactions and from the central chromium(III) ion cancel out almost exactly. As a consequence, the easy‐axis anisotropy of Fe₃CrPh is entirely due to the peripheral, hard‐axis‐type iron(III) ions, the anisotropy tensors of which are necessarily orthogonal to the threefold molecular axis. A similar contribution from peripheral ions is expected to rule the magnetic anisotropy in the tetra‐iron(III) complexes currently under investigation in the field of molecular spintronics.