Showing papers in "European Journal of Inorganic Chemistry in 2013"

A General Strategy for the Synthesis of Functionalised UiO‐66 Frameworks: Characterisation, Stability and CO2 Adsorption Properties

Abstract: A general synthetic strategy has been developed, which can be used for the preparation of all the known as well as five new functionalised UiO-66-X compounds [X = H, F, F-2, Cl, Cl-2, Br, Br-2, I, CH3, (CH3)(2), CF3, (CF3)(2), NO2, NH2, OH, (OH)(2), OCH3, (CO2H)(2), SO3H, C6H4]. Starting from a reaction mixture of ZrOCl2 center dot 8H(2)O, H2BDC-X (BDC: 1,4-benzenedicarboxylate), formic acid and N,N-dimethylacetamide (DMA) having a molar ratio of 1:1:100:104.44, all the UiO-66-X compounds, except UiO-66-CO2H, were obtained under solvothermal conditions (150 degrees C, 24 h). The phase purity of all the compounds was ascertained by X-ray powder diffraction (XRPD) analysis, DRIFT spectroscopy and elemental analysis. Determination of lattice parameters from the XRPD patterns of the new thermally activated UiO-66-X {X = CF3 (1-CF3), (CO2H)(2) [2-(CO2H)(2)], F-2 (3-F-2), Cl-2 (4-Cl-2), Br-2 (5-Br-2)} compounds revealed their structural similarity with the unfunctionalised UiO-66. Thermogravimetric analyses (TGA) indicate that the five new compounds are stable in the range 290-390 degrees C in air. Except for 3-F-2, the new compounds maintain their structural integrity in water, acetic acid and 1 M HCl, as verified by XRPD analysis of the samples recovered after suspending them in the respective liquids. As confirmed by N-2 and CO2 sorption analyses, all of the new thermally activated compounds exhibit significant microporosity values (S-Langmuir = 217-836 m(2)g(-1)), which are lower than that of the parent UiO-66. Comparative CO2 sorption studies reveal that the UiO-66-X compounds with X = NO2, NH2, OH, CH3 and (CH3)(2) show enhanced CO2 uptake compared to that of the parent compound at 1 bar and 0 degrees C.

Nitrogen-Rich Salts of 1H,1′H-5,5′-Bitetrazole-1,1′-diol: Energetic Materials with High Thermal Stability

Abstract: 1H,1′H-5,5′-Bitetrazole-1,1′-diol was synthesized starting from glyoxal, which is converted to glyoxime after treatment with hydroxylamine. Chlorination of glyoxime with Cl2 gas in ethanol and following chloro/azido exchange yields diazidoglyoxime, which is cyclized under acidic conditions (HCl gas in diethyl ether) to give 1H,1′H-5,5′-bitetrazole-1,1′-diol dihydrate (1). A large variety of nitrogen-rich salts of 1 such as the diammonium (2), the dihydrazinium (3), the bis-guanidinium (4), the bis(aminoguanidinium) (5), the diaminoguanidinium salt monohydrate (6), the triaminoguanidinium salt monohydrate (7), the 1-amino-3-nitroguanidinium salt dihydrate (8), the diaminouronium salt monohydrate (9), the bis(oxalyldihydrazidinium) (10), the oxalyldihydrazidinium salt dihydrate (11), the 3,6-dihydrazino-1,2,4,5-tetrazinium (12), the 5-aminotetrazolium (13), the bis(5-amino-1-methyl-1H-tetrazolium) salt (14), the bis(5-amino-2-methyl-2H-tetrazole) adduct (15), and the 1,5-diaminotetrazolium salt (16) were synthesized by means of Bronsted acid–base or metathesis reactions. All compounds were fully characterized by vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC) measurements. The crystal structures of 1–16 could be determined by using single-crystal X-ray diffraction. The heats of formation of 1–16 were calculated by using the atomization method on the basis of CBS-4M enthalpies. With regard to their potential use as cyclotrimethylene trinitramine (RDX) or hexanitrostilbene (HNS) replacements, several detonation parameters such as the detonation pressure, detonation velocity, explosion energy, and explosion temperature were computed using the EXPLO5 code on the basis of the experimental (X-ray) densities and calculated heats of formation. In addition, the sensitivities towards impact, friction, and electrical discharge were tested using the BAM drop hammer, a friction tester, as well as a small-scale electrical discharge device.

A Comprehensive Survey of Cationic Iridium(III) Complexes Bearing Nontraditional Ligand Chelation Motifs

Abstract: The useful optoelectronic properties of cationic iridium(III) complexes have been exploited in diverse applications, from visual displays to biological probes to analytical sensors. It is thus not surprising to note the increased recent efforts to document, understand, and ultimately control the photophysical and electrochemical properties of the archetypal cationic iridium(III) complex [(ppy)2Ir(bpy)]+, in which ppyH = 2-phenylpyridine and bpy = 2,2′-bipyridine, and decorated versions thereof. Of the ligand architectures explored, the greatest attention has been devoted to ligands that incorporate the common pyridine unit. In this Microreview, we survey the salient emission and electrochemical properties of cationic iridium(III) complexes of the form [(C∧N)2Ir(L∧X)]+, in which C∧N is a cyclometalating ligand and L∧X is a bidentate neutral ancillary ligand, with at least one heterocyclic ligand other than pyridine. We contrast their properties to that of [(ppy)2Ir(bpy)]+ and highlight recent exploits in materials applications.

Spin Crossover at the Nanometre Scale

Abstract: From the development of new methods for the synthesis and patterning of nanometre‐scale thin films and particles, to the first investigations of charge transport and photonic properties, there has been a proliferation of research concerning spin crossover nanomaterials in recent years. Studies have aimed at addressing fundamental questions concerning size‐reduction effects, as well as striving towards practical applications in this important class of bistable molecular materials. This microreview describes the most recent achievements and highlights possible future directions in this field.

Spin Crossover – Quo Vadis?†

Abstract: This retrospective essay is an attempt to span the bridge over eight decades of research on spin crossover (SCO), one of the most fascinating dynamic electron structure phenomena of inorganic coordination chemistry. The occurrence of SCO compounds of 3d transition metal ions and their characterization regarding magnetic, optical, vibrational, structural, and thermodynamic properties are briefly addressed. Selected case studies of chemical influences and physical effects (pressure, magnetic field, light) on SCO behavior are discussed. Particular attention is paid to the importance of Mossbauer spectroscopy in SCO studies. Light-induced excited spin state trapping (LIESST) and related photophysical phenomena involving SCO compounds are briefly highlighted. The remarkable instrumental improvements over the years and the amazing widespread developments in synthesizing new SCO compounds up to multifunctional materials currently in the foreground of SCO research are brought to light in a state-of-the-art summary. New directions, primarily towards applications, are mentioned.

Terminal Oxo and Imido Transition‐Metal Complexes of Groups 9–11

Abstract: This review summarizes the properties of group 9–11 metal–oxo and metal–imido complexes, which have been either isolated or proposed as reactive intermediates in metal-catalyzed organic transformations. We begin with a general description of the bonding of transition-metal–oxo and –imido complexes in various geometries, followed by a discussion of complexes from groups 9–11. The focus of this review is to provide a clear picture of the state of the art as well as insight towards potential future synthetic endeavors.

Polyoxometalates as Versatile Enzyme Inhibitors

Abstract: Polyoxometalates (POMs) are inorganic cluster compounds that have been shown to possess a number of pharmacological properties, including antidiabetic, antibacterial, antiprotozoal, antiviral and anticancer activities Their molecular mechanism of action is largely unknown However, several studies indicate that many of their activities may be due to the inhibition of enzymes, in particular, of those enzymes that are accessible from the extracellular space and do not require the penetration of cell membranes In this review, we describe the recent progress in the preparation and optimization of POMs, and an evaluation of their use as inhibitors of different families of enzymes The next important steps in this area of research will be to gain a better understanding of the interactions of POMs with enzymes on a structural level through an X-ray crystallographic study of enzyme–POM complexes and the analysis of structure–activity relationships Furthermore, POMs with increased stability and in vivo half-lives have to be prepared Surface modification may allow the targeting of POM drugs at their sites of action

Developments in the Coordination Chemistry of Phosphinines

Abstract: Invited for this month's cover is the group of Christian Muller at the Freie Universitat Berlin. The image shows the most recent developments in the coordination chemistry of functionalized, π-accepting phosphinines.

Spin Crossover and Thermochromism of Iron(II) Coordination Compounds with 1,2,4‐Triazoles and Tris(pyrazol‐1‐yl)methanes

Abstract: We review herein the synthesis and investigation of iron(II) coordination compounds with 1,2,4-triazoles or tris(pyrazol-1-yl)methanes as ligands. Both groups of complexes demonstrate thermally induced spin crossover accompanied by thermochromism [pink (magenta) ↔ white color change]. Factors that influence the nature and temperature of the spin crossover are discussed.

Biologically Relevant Silver(I)–N‐Heterocyclic Carbene Complexes: Synthesis, Structure, Intramolecular Interactions, and Applications

Abstract: N-Heterocyclic carbenes (NHCs) complexed with silver represent new, broad-spectrum antimicrobial and anticancer agents, normally with low toxicity profiles, and they provide a range of versatile structures for targeted biological applications. Most of these complexes have shown higher cytotoxicity than cisplatin, a potent anticancer drug. This study reviews the design, synthesis, structural characterization, and biological applications of silver complexes derived from both functionalized and nonfunctionalized NHC ligands. Specifically, silver complexes of functionalized and nonfunctionalized imidazole- and benzimidazole-based NHC systems employed in antimicrobial and anticancer applications are

Copper(I) Oxide Nanocrystals – One Step Synthesis, Characterization, Formation Mechanism, and Photocatalytic Properties

Abstract: We report here two different simple, one-pot, and low cost chemical synthetic routes for the preparation of Cu2O nanocrystals: (a) thermal decomposition of copper–organic precursors copper(II) acetate or copper(II) acetylacetonate in long chain organic solvents oleyl alcohol and trioctylamine, respectively, at 170 °C and (b) a surfactant-free solvothermal approach involving the reaction of copper(II) acetylacetonate in acetone at 140 °C. The structure and morphology of the nanocrystals have been characterized in detail by XRD, FTIR spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The optical properties of the nanocrystals have been explored by diffuse-reflectance spectroscopy (DRS) and a blueshift of the optical band gap of the nanocrystals is observed owing to size effects. Based on the FTIR, GC–MS, and 13C{1H} NMR studies of post-reaction solutions, different formation mechanisms for the Cu2O nanocrystals, which depend on the synthetic approach, have been proposed. Oleyl alcohol and trioctylamine play dual roles as solvents and mild reductants and reduce CuII species to CuI species during the course of the thermal decomposition reactions. The solvothermal reaction of copper(II) acetylacetonate in acetone possibly proceeds by acetylacetone-mediated reduction of Cu2+ to Cu+ in the absence of any reducing agent. The potential of Cu2O nanocrystals as photocatalytic materials for hydrogen generation from water/methanol (2:1) mixtures under UV/Vis irradiation has also been evaluated. The results show that all the nanocystalline Cu2O samples generate H2.

Small‐Molecule Activation at Uranium(III)

Abstract: Over the last 15 years or so, it has been shown that low-valent, electron-rich uranium(III) complexes exhibit a wide variety of reactivity towards small molecules. As a result, the field of uranium-mediated small-molecule activation chemistry has undergone significant development in recent years. The classical organometallic reactivity patterns of oxidative addition and reductive elimination that dominate the chemistry of transition-metal complexes are much less common for uranium. Owing to the invocation of the 5f orbitals for bonding and the highly polarising nature of the actinide centre, the prevalent reactivity observed for non-aqueous uranium compounds is that of migratory insertion, σ-bond metathesis and redox activity, and this can account for the often unexpected chemistry encountered with these species. This microreview focuses on the activation chemistry of trivalent uranium complexes towards the important small molecules dinitrogen (N2), nitric oxide (NO), azide (N3–), carbon monoxide (CO) and carbon dioxide (CO2).

Mesoporous Carbon Incorporated with In2O3 Nanoparticles as High‐Performance Supercapacitors

Abstract: Well-organized mesoporous carbon impregnated with In2O3 nanoparticles can be used as supercapacitor electrodes. The uniformly distributed In2O3 nanoparticles in the mesoporous carbon matrix are effectively utilized for the enhancement of capacitive performance.

Progress in Electronic Structure Calculations on Spin-Crossover Complexes

Abstract: Spin-crossover (SCO) complexes are an ongoing challenge to quantum chemistry due to the delicate balance of their electronic and entropic contributions to the adiabatic enthalpy difference between the high- and low-spin states. This challenge has fuelled an improvement in the existing quantum chemical methods and the development of new ones and will continue to do so. The progress in electronic structure calculations performed on SCO complexes in recent years has made quantum chemical methods valuable tools that may aid the design of new SCO compounds with desirable features. Post-Hartree–Fock ab initio methods can be used to calculate the adiabatic energy difference between high- and low-spin states with satisfactory accuracy but are currently limited to model systems or smaller molecular SCO complexes. The results obtained by these methods serve as references for other electronic structure calculations that may also be applied to larger systems. The methods of choice for the calculation of geometries and molecular vibrations of isolated SCO complexes and of crystalline compounds are based on density functional theory (DFT). Recent hybrid functionals can be used to calculate the adiabatic energy difference to an accuracy that is in some cases close to that of ab initio calculations, although no unique functional has been identified up to now that is superior to other functionals in all cases. DFT methods can now also be applied to crystalline systems and allow intermolecular effects to be investigated that are important for understanding the cooperativity of spin transitions.

The Templating Effect and Photochemistry of Viologens in Halometalate Hybrid Crystals

Abstract: Invited for this month's cover is the group of Nicolas Mercier at Moltech-Anjou CNRS, Universite Angers. The image shows the most recent developments in the chemistry of viologens in halometalate hybrid crystals.

Crystal Structures and Spin Crossover in the Polymeric Material [Fe(Htrz)2(trz)](BF4) Including Coherent-Domain Size Reduction Effects

Abstract: The high-spin and low-spin crystal structures of [Fe(Htrz)2(trz)](BF4) (Htrz = 1H-1,2,4-triazole, trz- = deprotonated triazolato ligand) were determined and refined on the basis of X-ray diffraction data obtained from a high-quality crystalline powder. Noteworthy differences to the previously reported structural hypothesis are obtained, which includes a revision of the space group to orthorhombic Pnma. Notably, the distinction between the positions of the Htrz and the trz- ligand along the chains reveals their respective roles in the formation of direct interchain interactions. The latter are also mediated by the anions. In addition, the pair-distribution-function (PDF) method was applied to investigate the potential modification of the crystal structure by a reduction of the coherent-domain size from 50 nm to 10 nm. First, the PDF investigation confirms the validity of the crystal structures presented here. Furthermore, in a first approach, it reveals that the crystal structure description remains suitable for the whole range of coherent-domain sizes investigated.

Coordination-Driven Self-Assembly of Arene–Ruthenium Compounds

Abstract: The coordination-driven self-assembly of N-donor ligands with dinuclear arene–ruthenium building blocks has allowed the construction of a wide range of cationic supramolecules with different architectures and functionalities. These supramolecules include (1) hexacationic molecular metallaprisms in which the size of the cycle and type of the arene–ruthenium acceptor and organic linker influence the antitumor behavior of the resulting self-assembly, and (2) tetracationic molecular metallarectangles, which have host–guest capabilities and allow sensing of biological properties. This report covers the synthetic and structural aspects of these coordination-driven self-assembled supramolecules as well as their most promising applications, with a particular focus on potential biological, sensing, and host–guest applications.

Activating Azides and Alkynes for the Click Reaction with [Cu(aNHC)2I] or [Cu(aNHC)2]+ (aNHC = Triazole‐Derived Abnormal Carbenes): Structural Characterization and Catalytic Properties

Abstract: Neutral, iodido-containing copper(I) complexes [Cu(aNHC)2I] {aNHC = 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 6) and 3-methyl-1-[2-(methylthio)phenyl]-4-phenyl-1,2,3-triazol-5-ylidene (for 7)} and cationic, halide-free copper(I) complexes [Cu(aNHC)2](BF4) {aNHC = 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 8), 3-methyl-1,4-diphenyl-1,2,3-triazol-5-ylidene (for 9), 3-methyl-1-[2-(methylthio)phenyl]-4-phenyl-1,2,3-triazol-5-ylidene (for 10), and 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 11)}, both containing two monodentate abnormal-carbene ligands (aNHC), were synthesized from [Cu(CH3CN)4](BF4) and the corresponding triazolium salts. It was possible to selectively synthesize both kinds of complexes by simply variing the counter-anion of the triazolium salts and keeping the metal precursor the same. All complexes were characterized by elemental analysis and spectroscopic methods. 6 and 11 were studied with single-crystal X-ray diffraction analyses. In 6, the copper(I) center is tricoordinated, and its geometry is in between trigonal planar and T-shaped. In halide-free 11, the copper(I) center is linearly coordinated by two abnormal-carbene ligands. All complexes were tested as catalysts in the Huisgen [3+2] cycloaddition reaction between azides and alkynes, and they showed excellent efficiencies under neat conditions. A comparison between the efficiencies of the halide-containing complexes 6 and 7 and the halide-free cases 8–11, shows that the halide-free Cu–aNHC complexes are significantly more efficient than their halide-containing counterparts. The best catalyst was used for a substrate screening by utilizing a variety of azides and a couple of alkynes. The efficiency of the catalyst was maintained with loadings as low as 0.005 mol-%. Mechanistic studies were carried out as well.

Dinitrogen Activation at Iron and Cobalt Metallalumatranes

Abstract: Anionic cobalt and iron metallalumatranes that bind dinitrogen in an end-on fashion were prepared and characterized by X-ray crystallography. Along with literature-known neutral cobalt and iron metallalumatranes, they form a quartet of low-valent coordination complexes for comparing dinitrogen activation and functionalization at cobalt versus iron centers. In the anionic metallalumatranes, the metal atoms are proposed to have subvalent oxidation states of –1. The electronic structure of the anionic iron alumatrane, which was probed by electron paramagnetic resonance spectroscopy, Mossbauer spectroscopy, and density functional theory, is most consistent with Fe(–1)Al(+3). Functionalization of dinitrogen was achieved by reaction of the ferrate alumatrane with 1,2-bis(chlorodimethylsilyl)ethane and KC8 (1 equiv.) to generate an iron(II) disilylhydrazido complex. The transformation of dinitrogen to disilylhydrazido(2–) is an overall four-electron process.

Color and Brightness Tuning in Heteronuclear Lanthanide Terephthalate Coordination Polymers

Abstract: Heteronuclear lanthanide terephthalate coordination polymers with the general chemical formula [Ln2-2xLn2x(bdc)3(H2O)4], for which bdc2- symbolizes benzene-1,4-dicarboxylate (or terephthalate) and Ln and Ln represent trivalent rare earth ions, were synthesized and structurally characterized. Analysis of the Y/Lu compounds by 89Y and 13C solid-state NMR spectroscopy was carried out, and the results support the hypothesis of randomly distributed lanthanide ions. The spectroscopic and colorimetric properties of this family of compounds were investigated in detail. The resulting data demonstrate that this series of compounds presents highly tunable luminescence properties and clearly indicate that intermetallic deactivation processes play an important role in the emission mechanism. Playing with intermetallic distances allows one to tune the color and the brightness of the lanthanide emission in these coordination polymers.

N-Methyl-4,4′-bipyridinium and N-Methyl-N′-oxide-4,4′-bipyridinium Bismuth Complexes – Photochromism and Photoluminescence in the Solid State

Abstract: Three bismuth complexes based on N-methyl-4,4′-bipyridinium (hMV+), (hMV)[Bi(hMV)Cl5] (1), and N-methyl-N′-oxide-4,4′-bipyridinium (MVO+), [Bi(MVO)X4(dmso)]·dmso [X = Cl (2), Br (3)], are reported. All three compounds show luminescence in the solid state with maxima at 545 nm (yellow for 1) and 560 nm (orange for 2 and 3) with quantum yields up to 10 %. Upon UV irradiation, 1 undergoes a color change from white to blue accompanied by a reduction of the photoluminescence intensity. The analysis of the crystal structure of the three complexes points to a photoinduced charge-transfer (PICT) process at the origin of the photochromism in 1.

Incorporation of Hydrogen-Bonding Functionalities into the Second Coordination Sphere of Iron-Based Water-Oxidation Catalysts

Abstract: Energy storage and conversion schemes based on environmentally benign chemical fuels will require the discovery of faster, cheaper, and more robust catalysts for the oxygen-evolution reaction (OER). Although the incorporation of pendant bases into molecular catalysts for hydrogen production and utilization has led to enhanced turnover frequencies, the analogous incorporation of pendant bases into molecular catalysts for water oxidation has received little attention. Herein, the syntheses, structures, and catalytic activities of new iron complexes with pendant bases are reported. Of these new complexes, [Fe(L^1)]^(2+) {L^1 = N,N′-dimethyl-N,N′-bis(pyridazin-3-ylmethyl)ethane-1,2-diamine} is the most active catalyst. Initial turnover frequencies of 141 and 24 h^(–1) were measured by using ceric ammonium nitrate at pH 0.7 and sodium periodate at pH 4.7, respectively. These results suggest that the incorporation of pendant bases into molecular catalysts for water oxidation might be an effective strategy that can be considered in the development of new catalysts for the OER, but will require the careful balance of many factors.

Ligand Effects on Bonding and Ion Pairing in Cationic Gold(I) Catalysts Bearing Unsaturated Hydrocarbons

Abstract: We critically review recent experimental and theoretical investigations into some key aspects of the chemistry of gold(I) complexes of the type [L–Au–S]+X– (L = NHC carbenes and phosphanes, S = alkenes and alkynes, and X– = weakly coordinating counterion). These systems are important intermediates formed during gold-catalyzed nucleophilic additions to an unsaturated substrate, and their specific activity is largely governed by two fundamental factors: the nature of the gold–substrate bond and the role of the ion-pair structure in solution. Both are crucially influenced by the nature and properties of the auxiliary ligand L, and on this interplay we focus our discussion. The relative anion–cation orientation, investigated by NOE NMR spectroscopy and DFT calculations, shows that the exact position of the counterion is determined by the natures of the ancillary ligand and substrate: the counterion is located near the substrate in the phosphane complexes, while for the NHC complexes the preferred position of the counterion is near the ligand. This tunable interionic structure opens the way to greater control over the properties and activity of these catalysts. The bond between AuI and the unsaturated substrate is investigated using an original and powerful theoretical method of analysis. Our approach permits a rigorous definition and assessment of the charge-displacement (CD) components at the heart of the Dewar–Chatt–Duncanson model: substrate-to-metal (σ donation) and metal-to-substrate (π back-donation) and how these change with different ligands. The results consistently reveal that π back-donation is a large and crucially important component of the AuI–substrate bond in all systems: π back-donation penetrates the external side of coordinated alkynes, where nucleophile attack is directed, thus partially mitigating the electron depletion caused by σ donation.

Synthesis and Exfoliation of Layered α‐Co(OH)2 Nanosheets and Their Electrochemical Performance for Supercapacitors

Abstract: A novel facile approach has been developed to prepare graphene-like α-Co(OH)2 two-dimensional ultrathin nanosheets. The layered hydrotalcite-like α-Co(OH)2 aggregates were successfully exfoliated in formamide solution in a constant temperature oscillator. The influence of exfoliation on the thickness and surface structure of the Co(OH)2 monolith was analyzed by scanning electron microscopy and transmission electron microscopy. After the exfoliation process, the electrochemical performances of the 2D α-Co(OH)2 nanosheets were tested by cyclic voltammetry, galvanostatic discharge/charge, and electrochemical impedance spectroscopy. Impressively, the charge/discharge study shows that the exfoliated sample is capable of delivering a high specific capacitance of 952 F g–1 at a current density of 5 mA cm–2 and maintains 48 % of the capacitance when the current density is as high as 50 mA cm–2. In addition, the exfoliated Co(OH)2 nanosheets also exhibited excellent cycling stability and is an excellent electrode material for high-performance supercapacitors. Our work not only presents a cost-effective and scalable method for the synthesis of α-Co(OH)2 nanosheets with a high surface area, but also holds promise for the synthesis of a series of other graphene-like laminar structures with high specific surface areas for electrochemical energy storage, catalysis, gas sensing, and other applications.

A Solid‐Solution Approach to Mixed‐Metal Metal–Organic Frameworks – Detailed Characterization of Local Structures, Defects and Breathing Behaviour of Al/V Frameworks

Abstract: Invited for the cover of this issue is the group of Roland Fischer at Ruhr University Bochum. The cover image shows that the structure/properties of materials vary as the complexity of the framework is increased and different metals are combined in single-phased MOFs.

Preparation of 2‐Alkylidene‐Substituted 1,3,4,5‐Tetramethylimidazolines and Their Reactivity Towards RhI Complexes and B(C6F5)3

Abstract: In addition to the known 1,3,4,5-tetramethyl-2-methyleneimidazoline (1a), which exhibits a highly polarized exocyclic C–C bond, a series of novel 2-alkylidene-substituted 1,3,4,5-tetramethylimidazolines 1b–e were synthesized and characterized. The molecular structures of 1b, 1d, and 1e were determined by X-ray diffraction analysis and revealed an increase in the polarization of the exocyclic C–C bond with increasing steric demand of the 2-substituent. On the basis of their ylidic nature, 1a–e show enhanced basicity and reactivity towards Lewis acidic centers. Treatment of 1a and 1b with [{RhCl(cod)}2] or B(C6F5)3 afforded complexes of the type [(L)RhCl(cod)] (4a,b), [(L)RhCl(CO)2] (7a,b) (L = 1a,b) or classical Lewis acid/base adducts [(1a)B(C6F5)3] (8a) and [(1b)B(C6F5)3] (8b). In contrast, complexes [(L)RhCl(cod)] with 1c and 1d as ligands are not stable, and imidazolium dichlororhodate salts 6a and 6b were isolated instead. Rhodium–alkyl complexes 5a and 5b are assumed to be intermediates in this decomposition process, and 5a was characterized by X-ray diffraction analysis. Furthermore, treatment of 1c and 1d with B(C6F5)3 did not afford classical Lewis adducts, and instead imidazolium hydridoborate salts 9a and 9b are formed by hydride abstraction. Surprisingly, we found that 1e does not react with [{RhCl(cod)}2] and forms an abnormal Lewis adduct 10 when treated with B(C6F5)3.

Hydrothermal Synthesis of Binary Ni–Co Hydroxides and Carbonate Hydroxides as Pseudosupercapacitors

Abstract: A series of binary Ni-Co hydroxides and Ni-Co carbonate hydroxides with various shapes and compositions was successfully synthesized by a one-step and reliable method assisted by an amphiphilic block copolymer. After thermal treatment at 200 degrees C, the as-prepared samples could be activated and their surface areas could be increased. With increasing Co content, the shapes of the final products changed from flower-to fiber-and plate-like structures. The synthesized binary Ni-Co sample with an optimized composition of Ni2+/Co2+ = 25:75 exhibited high surface area and a capacitance of 632 Fg(-1) at 5 mVs(-1) with negligible capacitance loss after 1000 cycles. The capacitance value of the binary Ni-Co sample is higher than that of Ni hydroxide itself, and this improved electrochemical performance is attributed to the binary Co2+/Co3+ and Ni2+/Ni3+ couples that afford rich faradic capacitance and enhanced conductivity.

Efficient and Rapid Synthesis of Chlorido‐Bridged Half‐Sandwich Complexes of Ruthenium, Rhodium, and Iridium by Microwave Heating

Abstract: The dinuclear complexes [(p-cymene)RuCl2]2 and [(cyclopentadienyl)MCl2]2 (M = Ru, Rh, Ir) are important starting materials in organometallic chemistry. The standard synthesis of these complexes involves heating of an alcoholic solution of RuIII, RhIII, or IrIII salts with precursors of the π-ligands for several hours under reflux. Microwave heating allows these complexes to be obtained within a few minutes without compromising the yields. Furthermore, the microwave-assisted syntheses require less solvent and, in some cases, lower amounts of ligand precursors.

An Updated View of Cisplatin Transport

Abstract: Invited for the cover of this issue is the group of Giovanni Natile at the University of Bari. The cover image poses the question whether platinum exchange occurs between transporters as it happens for copper – a major question still lacking an answer. In the background is “the near-touching hands”, a detail of the Creation of Adam by Michelangelo.

A Floating Porous Crystalline TiO2 Ceramic with Enhanced Photocatalytic Performance for Wastewater Decontamination

Abstract: A highly porous TiO2 ceramic floating photocatalyst was successfully synthesized by using ethanediamine-modified Degussa P25 as precursor, followed by a camphene-based freeze-casting process and high-temperature calcination. The ceramics were characterized in detail by XRD, SEM, and TEM. The results indicate that an ethanediamine protector can inhibit undesirable titania grain growth and phase transformation during calcination. The porosity and compressive strength of the ceramics varies with sintering temperatures; the optimal sintering temperature, 800 °C, produces high porosity, high compressive strength, and high photocatalytic activity. The ceramics exhibit good photocatalytic activity for the photodegradation of rhodamine B (10 mg L–1), and the total organic carbon removal efficiency is up to 96.7 % after 5 h. The photocatalytic kinetics of rhodamine B removal are pseudo-first order. The ceramics are recyclable, and no clear changes are observed after six cycles. Furthermore, the ceramics are also active in phenol, thiobencarb, atrazine, and octane. Therefore, this novel floating photocatalyst will likely have wide applications, including the removal of soluble organic pollutants from wastewater or the removal of oil pollutants from wastewater surfaces.