Synergistic Effect of Redox Dual PdO x /MnO x Cocatalysts on the Enhanced H2 Production Potential of a SnS/α-Fe2O3 Heterojunction via Ethanol Photoreforming.

In the quest for optimal H2 evolution (HE) through ethanol photoreforming, a dual cocatalyst-modified heterocatalyst strategy is utilized. Tin(II) sulfide (SnS) was hybridized with α-Fe2O3 to form the heterocatalyst FeOSnS with a p-n heterojunction structure as confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffusive reflectance spectroscopy (UV-vis DRS), and Brunauer-Emmett-Teller (BET) techniques. PdO x and PdO x /MnO x cocatalysts were loaded onto the FeOSnS heterocatalyst through the impregnation method, as verified by high-resolution transform electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and elemental mapping. Photocatalytic ethanol photoreforming resulted in the production of H2 as the main product with a selectivity of 99% and some trace amounts of CH4. The FeOSnS2-PdO x 2%/MnO x 1% photocatalyst achieved the highest HE rate of 1654 µmol/g, attributed to the synergistic redox contribution of the PdO x and MnO x species.

Against the Norm: Non Irving-Williams Transmetalation in Transition Metal Dimers.

We report the synthesis and characterization of three dinuclear 3d3d' complexes, CuCu ([Cu2IIL(NO3)2]), MnMn ([Mn2IIL(MeOH)2(NO3)2]), and CuMn ([CuIIMnIIL(NO3)2]), that utilize the ligand, H2L (6,6'-dimethoxy-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol). The relative stabilities of these complexes were investigated using experimental and computational techniques, revealing a non-Irving-Williams transmetalation, whereby a MnII ion can displace a CuII ion from its binding pocket in CuCu to yield the more stable CuMn complex. Magnetic characterization of the reported complexes revealed an unexpected ferromagnetic coupling between the two CuII ions of CuCu with J = +63.0 cm-1.

From Gas Phase Observations to Solid State Reality: The Identification and Isolation of Trinuclear Salicylaldoximato Copper Complexes.

Conditions have been identified in which phenolic aldoximes and ketoximes of the types used in commercial solvent extraction processes can be doubly deprotonated and generate polynuclear Cu complexes with lower extractant:Cu molar ratios than those found in commercial operations. Electrospray mass spectrometry has provided an insight into the solution speciation in extraction experiments and has identified conditions to allow isolation and characterization of polynuclear Cu-complexes. Elevation of pH is effective in enhancing the formation of trinuclear complexes containing planar {Cu3-µ3-O}4+ or {Cu3-µ3-OH}5+ units. DFT calculations suggest that such trinuclear complexes are more stable than other polynuclear species. Solid structures of complexes formed by a salicylaldoxime with a piperidino substituent ortho to the phenolic OH group (L9H2) contain two trinuclear units in a supramolecular assembly, {[Cu3OH(L9H)3(ClO4)](ClO4)} 2, formed by H-bonding between the central {Cu3-µ3-OH}5+ units and oxygen atoms in the ligands of an adjacent complex. Whilst the lower ligand:Cu molar ratios provide more efficient Cu-loading in solvent extraction processes, the requirement to raise the pH of the aqueous phase to achieve this will make it impractical in most commercial operations because extraction will be accompanied by the precipitation (as oxyhydroxides) of Fe(III) which is present in significant quantities in feed solutions generated by acid leaching of most Cu ores.

Lanthanide induced variability in localised CoII geometries of four triangular L3Co3 IILnIII complexes.

Four tetranuclear heterobimetallic triangle complexes [L3Co3Dy(NO3)2(H2O)(MeOH)5](NO3) (C1), [L3Co3Gd(NO3)3(MeOH)4] (C2), [L3Co3La(NO3)2(H2O)6](NO3)(H2O) (C3), and [L3Co3TbCl(NO3)2(H2O)0.5(MeOH)3.5] (C4), where H2L = 1,4-bisformylnaphthalene-2,3-diol, have been synthesised and structurally characterised. Each complex crystallises with a complete molecule in the asymmetric unit (Z' = 1) and displays near perfect octahedrality in two out of three CoII centres. The third CoII ion assumes a different coordination geometry in each complex: six-coordinate octahedral in C1, six-coordinate with a distortion towards trigonal prismatic in C2, five-coordinate trigonal bipyramidal in C3, and five-coordinate square pyramidal in C4; which has been attributed to increasing lanthanide cation size, coupled with a non-macrocyclic coordination environment. Continuous Shape Measurement (CShM) calculations and octahedral distortion parameter calculations were performed, using the SHAPE and OctaDist software packages, respectively, in order to aid in the assessment of each metal centre's local coordination geometry. The preliminary magnetic investigation of C3 found χ m T = 9.4 cm3 K mol-1 at 300 K and M = 7.1 µ B at 1.8 K, which are approximately two thirds the maximum theoretical values for three CoII ions and indicates the presence of a relatively large zero-field splitting parameter (D/k B = 65 K) operative in each CoII ion rather than exchange coupling between the CoII centres.

Metallocyclic CuII-LnIII Single-Molecule Magnets from the Self-Assembly of 1,4-Diformylnaphthalene-2,3-diol.

We report the synthesis and characterization of seven new tetranuclear 3d-4f complexes derived from the 3:3:1 reaction of 1,4-diformylnaphthalene-2,3-diol (H2 L) with copper(II) nitrate and a lanthanide salt, Ln = Tb [L 3Cu3TbCl2(NO3)2(H2O)2] (C1), Ho [L 3Cu3HoCl3(H2O)3(MeOH)](H2O) (C2), Er [L 3Cu3ErCl3(H2O)3.5(MeOH)0.5](H2O) (C3), Gd [L 3Cu3Gd(NO3)2(H2O)2(MeOH)](NO3) (C4), Dy [L 3Cu3Dy(NO3)2(H2O)2(MeOH)](NO3) (C5), Yb [L 3Cu3Yb(NO3)2(H2O)2(MeOH)](NO3) (C6), and La [L 3Cu3La(NO3)2(H2O)2(MeOH)](NO3) (C7). Structural elucidation showed that the self-assembly using the acyclic ligand system was successful for all seven complexes, which exhibit the same near-planar Cu3LnO12 core. Five complexes (C1, C2, and C4-C6) were magnetically characterized at 300 K and 1.8 K. Complexes C1, C4, and C5 were observed to have ferromagnetic ground states and showed appreciable frequency dependence in their AC magnetic measurements, which yielded effective barriers between 7.82(4) and 13.2(3) K, confirming the presence of single-molecule magnet properties.

Computational studies of the magneto-structural correlations in a manganese dimer with Jahn-Teller distortions.

Inspired by the crystal structure of a MnIII dinuclear complex we obtained featuring both Jahn-Teller (JT) elongation and compression distortions, we have modelled a series of complex cations based on the disordered crystal formulation; [Mn2(L1)2(µ2-OH)2)4+ (1), [Mn2(L1)(L2)(µ2-OH)2)4+ (2), [Mn2(L2)(L1)(µ2-OH)2)4+ (3), and [Mn2(L2)2(µ2-OH)2)4+ (4) (where L1 = (1E,1'E)-5-tert-butyl-3-(((4-(((5-tert-butyl-2-hydroxy-3-((E)-(hydroxyimino)methyl)benzyl)(methyl)amino)methyl)benzyl)(methyl)amino)methyl)-2-hydroxybenzaldehyde and L2 = 3,3'-(1,4-phenylenebis(methylene))bis(methylazanediyl)bis(methylene)bis(5-tert-butyl-2-hydroxybenzaldehyde)) with different geometries to investigate the effects of the distortions on the magnetic coupling parameter. All computationally modelled dimers had a ferromagnetic interaction between the MnIII centres, with greater magnetic coupling calculated for complexes with both JT elongation and compression present. The ferromagnetic contribution to the J coupling was ascribed to the orthogonality of the singly occupied magnetic orbitals along with the cross-interaction between the unfilled Mn1(dx2-y2) and singly occupied Mn2(dx2-y2) orbitals. Constrained calculations showed that reducing the extent of the compression at Mn2 results in a concomitant increase in the dihedral angle between the JT axes, thereby reducing the relative magnitude of the magnetic coupling between MnIII centres.

Self-assembly of non-macrocyclic triangular Ni3Ln clusters.

The synthesis and structural characterisation of four new heterometallic tetranuclear complexes is reported. Three L3Ni3Ln type complexes, where Ln = La (C1), Eu (C2), and Gd (C3), have been fully characterised including DC and AC magnetic measurements. A fourth complex featuring a diamagnetic BaII ion at its centre is also reported with structural characterisation. Structural elucidation showed that all four complexes successfully self-assembled from a stoichiometric mixture of the acyclic ligand, 1,4-diformylnaphthalene-2,3-diol, with nickel(II) nitrate and the appropriate heavy metal salt to produce the same near planar Ni3MO12 core. Ferromagnetic interactions were found to dominate the ground state of C3, exhibiting a maximal spin ground state of 13/2. The exchange coupling is quantitatively discussed along with the nickel(II) zero-field splitting effect. AC magnetic susceptibility experiments were carried out, but no frequency dependent signals were observed and thus no observable slow relaxation of magnetisation.

Iron Oxide Nanoparticles: Physicochemical Characteristics and Historical Developments to Commercialization for Potential Technological Applications.

Iron oxide nanoparticles (IONPs) have gained increasing attention in various biomedical and industrial sectors due to their physicochemical and magnetic properties. In the biomedical field, IONPs are being developed for enzyme/protein immobilization, magnetofection, cell labeling, DNA detection, and tissue engineering. However, in some established areas, such as magnetic resonance imaging (MRI), magnetic drug targeting (MDT), magnetic fluid hyperthermia (MFH), immunomagnetic separation (IMS), and magnetic particle imaging (MPI), IONPs have crossed from the research bench, received clinical approval, and have been commercialized. Additionally, in industrial sectors IONP-based fluids (ferrofluids) have been marketed in electronic and mechanical devices for some time. This review explores the historical evolution of IONPs to their current state in biomedical and industrial applications.

Quinolino[7,8-h]quinoline: a 'just right' ligand for beryllium(II) coordination.

We report the synthesis and crystal structure of the first quinolino[7,8-h]quinoline beryllium(II) complex of the general formula [BeL2(MeCN)Br]Br·MeCN, containing the ligand 4,9-dihydroxyquinolino[7,8-h]quinoline (L2). The Be(II) cation is a great size match for the dinitrogen binding pocket of the quinolino[7,8-h]quinoline ligand as indicated by minimal out-of-plane displacement and ligand distortion parameters.

Structural trends in a series of bulky dialkylbiarylphosphane complexes of CuI.

CuI complexes containing the bulky dialkylbiarylphosphane 2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl (tBuXPhos, L) and an ancillary ligand (Cl-, Br-, I-, MeCN, ClO4- or SCN-) have been structurally characterized, namely, chlorido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuCl(C29H45P)], 1, bromido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuBr(C29H45P)], 2, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]iodidocopper(I), [CuI(C29H45P)], 3, (acetonitrile-κN)[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I) hexafluoridophosphate, [Cu(CH3CN)(C29H45P)]PF6, 4, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP](perchlorato-κO)copper(I), [Cu(ClO4)(C29H45P)], 5, and di-µ-thiocyanato-κ2S:N;κ2N:S-bis{[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I)}, [Cu2(NCS)2(C29H45P)2], 6. Iodide complex 3 shows significant CuI-arene interactions, in contrast to its chloride 1 and bromide 2 counterparts, which is attributed to the weaker interaction between the iodide ion and the CuI centre. When replacing iodide with an acetonitrile (in 4) or perchlorate (in 5) ligand, the reduced interaction between the CuI atom and the ancillary ligand results in stronger CuI-arene interactions. No CuI-arene interactions are observed in dimer 6, due to the tricoordinated CuI centre having sufficient electron density from the coordinated ligands.

Synthesis and Characterization of Symmetrically versus Unsymmetrically Proton-Bridged Hexa-Iron Clusters.

Syntheses and magnetic and structural characterization of hexa-iron complexes of derivatized salicylaldoximes are discussed. Complexation of Fe(BF4)2·6H2O with each ligand (H2 L1 and H4 L2) in a methanolic-pyridine solution resulted in hexa-iron compounds (C1 and C2, respectively), which each contain two near-parallel metal triangles of [Fe3-µ3-O], linked by six fluoride bridges and stabilized by a hydrogen-bonded proton between the µ3-O groups. Within each metal triangle of C2, Fe(III) ions are connected via the amine "straps" of (H4 L2-2H). Variable-temperature magnetic susceptibility and Mössbauer data of C1 and C2 indicate the presence of dominant antiferromagnetic interactions between the high-spin (S = 5/2) Fe(III) centers. For C1, two quadrupole doublets are observed at room temperature and 5 K, consistent with structural data from which discrete but disordered [Fe3-µ3-O] and [Fe3-µ3-OH] species were inferred. For C2, a single sharp quadrupole doublet with splitting intermediate between those determined for C1 was observed, consistent with the symmetric [Fe3-µ3-O···H···µ3-O-Fe3] species inferred crystallographically from the very short µ3-O···µ3-O separation. The differences in the physical properties of the complexes, as seen in the Mössbauer, X-ray, and magnetic data, are attributed to the conformational flexibility imparted by the nature of the linkages between the closely related ligands.

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes.

Substituted [2.2]metaparacyclophanes are amongst the least studied of the simple cyclophanes. This is undoubtedly the result of the lengthy syntheses of these compounds. We report the simple synthesis of a rare example of a non-symmetric [2.2]metaparacyclophane. Treatment of [2.2]paracyclophane under standard nitration conditions gives a mixture of 4-nitro[2.2]paracyclophane, 4-hydroxy-5-nitro[2.2]metaparacyclophane and a cyclohexadienone cyclophane.

The structural manipulation of a series of Ni4 defective dicubanes: Synthesis, X-ray Structures, Magnetic and Computational analyses.

We report the synthesis and characterization of four new tetranuclear Ni(ii) complexes, C1-C4, all of which exhibit defective dicubane cores. C1-C4 are derived from the same salicylaldoxime derived ligand, H2L1. Complexes C1 and C4 have isostructural cores, differing in structure only by solvate molecules. Magnetic and computational analyses have revealed that complexes C1, C2, and C4 exhibit competing ferro- and antiferromagnetic interactions, however the different solvated species in C1 and C4 leads to notably different magnitudes in their magnetic coupling constants. Theoretical magneto-structural studies show that the pairwise magnetic exchange interaction is highly dependent on the Ni-X-Ni angle, as revealed by orbital overlap calculations.

Improvements in the Organic-Phase Hydrothermal Synthesis of Monodisperse M x Fe3-x O4 (M = Fe, Mg, Zn) Spinel Nanoferrites for Magnetic Fluid Hyperthermia Application.

In the quest for optimal heat dissipaters for magnetic fluid hyperthermia applications, monodisperse M x Fe3-x O4 (M = Fe, Mg, Zn) spinel nanoferrites were successfully synthesized through a modified organic-phase hydrothermal route. The chemical composition effect on the size, crystallinity, saturation magnetization, magnetic anisotropy, and heating potential of prepared nanoferrites were assessed using transmission electron microscopy (TEM), dynamic light scattering, X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), atomic absorption spectroscopy (AAS), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM) techniques. TEM revealed that a particle diameter between 6 and 14 nm could be controlled by varying the surfactant ratio and doping ions. EDS, AAS, XRD, and XPS confirmed the inclusion of Zn and Mg ions in the Fe3O4 structure. Magnetization studies via VSM revealed both the superparamagnetic nature of the nanoferrites and the dependence on substitution of the doped ions to the final magnetization. The broader zero-field cooling curve of Zn-doped Fe3O4 was related to their large size distribution. Finally, a maximum rising temperature (T max) of 66 °C was achieved for an aqueous ferrofluid of nondoped Fe3O4 nanoparticles after magnetic field activation for 12 min.

Synthesis and Basicity Studies of Quinolino[7,8-h]quinoline Derivatives.

Quinolino[7,8-h]quinoline is a superbasic compound, with a pKaH in acetonitrile greater than that of 1,8-bis(dimethylaminonaphthalene) (DMAN), although its synthesis and the synthesis of its derivatives can be problematic. The use of halogen derivatives 4,9-dichloroquinolino[7,8-h]quinoline (16) and 4,9-dibromoquinolino[7,8-h]quinoline (17) as precursors has granted the formation of a range of substituted quinolinoquinolines. The basicity and other properties of quinolinoquinolines can be modified by the inclusion of suitable functionalities. The experimentally obtained pKaH values of quinolino[7,8-h]quinoline derivatives show that N4,N4,N9,N9-tetraethylquinolino[7,8-h]quinoline-4,9-diamine (26) is more superbasic than quinolino[7,8-h]quinoline. Computationally derived pKaH values of quinolinoquinolines functionalized with dimethylamino (NMe2), 1,1,3,3-tetramethylguanidino (N═C(NMe2)2) or N,N,N',N',N″,N″-hexamethylphosphorimidic triamido (N═P(NMe2)3) groups are significantly greater than those of quinolino[7,8-h]quinoline. Overall, electron-donating functionalities are observed to increase the basicity of the quinolinoquinoline moiety, while the substitution of electron-withdrawing groups lowers the basicity.

Ab Initio Molecular Dynamics Investigation of Beryllium Complexes.

Structures of aqueous [Be(H2O)4]2+, its outer-sphere and inner-sphere complexes with F-, Cl-, and SO42-, and dinuclear complexes with a [Be2(κ-OH)(κ-SO4)]+ core have been studied through Car-Parrinello molecular dynamics (CPMD) simulations with the BLYP functional. According to constrained CPMD/BLYP simulations and pointwise thermodynamic integration, the free energy of deprotonation of [Be(H2O)4]2+ and its binding free energy with F- are 9.6 and -6.2 kcal/mol, respectively, in good accord with available experimental data. The computed activation barriers for replacing a water ligand in [Be(H2O)4]2+ with F- and SO42-, 10.9 and 13.6 kcal/mol, respectively, are also in good qualitative agreement with available experimental data. These ligand-substitution reactions are indicated to follow associative interchange mechanisms with backside (SN2-like) attack of the anion relative to the aquo ligand it is displacing. Outperforming static density functional theory computations of the salient kinetic and thermodynamic quantities involving simple polarizable continuum solvent models, CPMD simulations are validated as a promising tool for studying the structures and speciation of beryllium complexes in aqueous solution.

Towards more effective beryllium chelation: an investigation of second-sphere hydrogen bonding.

A comparative study between three experimentally known beryllium chelators (EDTA, NTP, and 10-HBQS) and two tetradentate tripodal di-pyridine-based receptors (HL and HL-NH2), specifically designed to bind Be2+ cations, has been undertaken in the aqueous phase at the B3LYP/6-311++G(d,p) computational level. The relative binding energies of these five ligand systems to a variety of first row and pre-transition metal cations have been calculated, specifically to investigate their binding strength to Be2+ and the binding enhancement that a second sphere hydrogen bonding interaction could afford to the pyridyl based systems. The complexes of EDTA were calculated to have the highest average binding energy; followed by those of NTP, HL-NH2, HL, and finally 10-HBQS. The calculated binding energy of the HL-NH2Be complex, which includes second sphere interactions, was found to be almost 9% greater than the HL Be complex, with an average binding energy increase of 13.5% observed across all metals upon inclusion of second sphere hydrogen bonding.

Tuning receptors for the encapsulation of beryllium2.

Two series of tetradentate tripodal di-pyridine-based receptors designed to bind Be2+ cations have been studied in the aqueous phase at the B3LYP/6-311++G(d,p) computational level. The first series comprise simple tetrahedral receptors; the second series incorporates additional scaffolding groups capable of second sphere hydrogen-bonding in order to more finely tune the binding strength towards the Be2+ cation. Out of the five ligand candidates, one containing a tri-pyridyl N-donor along with a phenolato O-donor (L1) exhibited a significant improvement in binding energy stabilisation (47.8 kJ mol-1) towards the Be2+ cation in the presence of second-sphere H-bonding interactions.

New salicylaldoximato-borate ligands resulting from anion hydrolysis and their respective copper and iron complexes.

Anion hydrolysis reactions between salicylaldoximato ligands (L'-L''') and copper and iron BF4- metal salts, have resulted in the formation of new salicylaldoximato borate containing transition metal complexes: [Fe2(L' + 2H)2](BF4)2(MeOH)4 (C1), [Fe3(L'' + 4H)(OH)2(Py)2](BF4)2(H2O)2(Py)2 (C2), and [Cu2(L''' + H)2Cl2] (C3). Each of the complexes have been structurally characterised, revealing the indirect role boron plays in the formation of these complexes. For complexes C1 and C2, Mössbauer spectroscopy confirmed the existence of Fe(iii) oxidation states. SQUID magnetometry measurements were performed on complexes C2 and C3, revealing the presence of two competing exchange pathways between the three Fe(iii) centres in C2, with antiferromagnetic exchange dominating. For C3 weak antiferromagnetic exchange dominated between the two Cu(ii) centres.

Electrospray Ionization Mass Spectrometric Study of the Gas-Phase Coordination Chemistry of Be2+ Ions with 1,2- and 1,3-Diketone Ligands.

Electrospray ionization mass spectrometry (ESI MS) is a powerful technique for the study of coordination complexes because of its ability to analyze solution systems involving very low concentrations of metal complexes. In this work, the coordination chemistry of Be ions with a selection of well-known 1,3-diketone and related 1,2-diketone ligands has been investigated using ESI MS. With acetylacetone (Hacac), a range of acac-containing ions is observed, including [Be(acac)2H]+, [Be(acac)(MeOH) n]+ ( n = 1, 2), and polynuclear species such as the dinuclear [Be2(acac)3]+ and trinuclear [Be3O(acac)3]+. Density functional theory calculations indicate that the latter species has a central Be3(µ3-O) core, with each Be chelated (as opposed to being bridged) by an acac ligand. The effect of changing the substituents on 1,3-diketone was explored by an investigation of mixtures of Be2+ with other 1,3-diketones such as dibenzoylmethane (Hdbm), where the [Be(dbm)2H]+ ion showed a lesser tendency to undergo fragmentation and aggregation processes. Comparisons with the corresponding aluminum acetylacetone system were also made. In contrast, mixtures of Be2+ and the 1,2-diketones diacetyl and phenanthrenequinone showed poor metal-ligand interactions. Be2+ interacted with the 1,2-diketone benzil [PhC(O)C(O)Ph], forming the [Be(benzil) n]2+ ( n = 2-4) ions. The synthesis (from BeCl2) and X-ray structures of the dibenzoylmethanato (dbm) complex Be(dbm)2 and the benzil complex [BeCl2(benzil)] are also reported.