Open AccessReview
The Supramolecular Attitude of Metal–Salophen and Metal–Salen Complexes
Inorganics 2018, 6(2), 42; doi:10.3390/inorganics6020042 -
Abstract
In this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this
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In this review we cover some aspects of metal–salophen and metal–salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this last point has been only briefly mentioned. Full article
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Open AccessArticle
Single Crystal Growth of Sillén–Aurivillius Perovskite Oxyhalides Bi4NbO8X (X = Cl, Br)
Inorganics 2018, 6(2), 41; doi:10.3390/inorganics6020041 -
Abstract
Sillén–Aurivillius perovskite Bi4NbO8X (X = Cl, Br) is a promising photocatalyst for water splitting under visible light, as well as a potential ferroelectric material. In this work, we investigate the crystal growth conditions by mainly varying soak temperature, soak
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Sillén–Aurivillius perovskite Bi4NbO8X (X = Cl, Br) is a promising photocatalyst for water splitting under visible light, as well as a potential ferroelectric material. In this work, we investigate the crystal growth conditions by mainly varying soak temperature, soak time and cooling rate. Under the optimal conditions, we successfully obtained yellow platelet single crystals with an in-plane distance of several hundred microns. As opposed to conventional crystal growth, a moderate cooling is essential to suppress an evaporation of the Bi–O–Cl species from a melt zone. The single crystals of Bi4NbO8Br were also grown using a similar condition. We suggest that the knowledge obtained in this study can be generally applied to other Sillén–Aurivillius phases and related oxyhalides. Full article
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Open AccessArticle
Effects of Introducing Methoxy Groups into the Ancillary Ligands in Bis(diimine) Copper(I) Dyes for Dye-Sensitized Solar Cells
Inorganics 2018, 6(2), 40; doi:10.3390/inorganics6020040 -
Abstract
A systematic investigation of four heteroleptic bis(diimine) copper(I) dyes in n-type Dye-Sensitized Solar Cells (DSSCs) is presented. The dyes are assembled using a stepwise, on-surface assembly. The dyes contain a phosphonic acid-functionalized 2,2′-bipyridine (bpy) anchoring domain (5) and ancillary bpy ligands
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A systematic investigation of four heteroleptic bis(diimine) copper(I) dyes in n-type Dye-Sensitized Solar Cells (DSSCs) is presented. The dyes are assembled using a stepwise, on-surface assembly. The dyes contain a phosphonic acid-functionalized 2,2′-bipyridine (bpy) anchoring domain (5) and ancillary bpy ligands that bear peripheral phenyl (1), 4-methoxyphenyl (2), 3,5-dimethoxyphenyl (3), or 3,4,5-trimethoxyphenyl (4) substituents. In masked DSSCs, the best overall photoconversion efficiency was obtained with the dye [Cu(5)(4)]+ (1.96% versus 5.79% for N719). Values of JSC for both [Cu(5)(2)]+ (in which the 4-MeO group is electron releasing) and [Cu(5)(4)]+ (which combines electron-releasing and electron-withdrawing effects of the 4- and 3,5-substituents) and are enhanced with respect to [Cu(5)(1)]+. DSSCs with [Cu(5)(3)]+ show the lowest JSC. Solid-state absorption spectra and external quantum efficiency spectra reveal that [Cu(5)(4)]+ benefits from an extended spectral range at higher energies. Values of VOC are in the order [Cu(5)(4)]+ > [Cu(5)(1)]+ > [Cu(5)(2)]+ > [Cu(5)(3)]+. Density functional theory calculations suggest that methoxyphenyl character in MOs within the HOMO manifold in [Cu(5)(2)]+ and [Cu(5)(4)]+ may contribute to the enhanced performances of these dyes with respect to [Cu(5)(1)]+. Full article
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Open AccessArticle
The Role of Neodymium in the Optimization of a Ni/CeO2 and Ni/CeZrO2 Methane Dry Reforming Catalyst
Inorganics 2018, 6(2), 39; doi:10.3390/inorganics6020039 -
Abstract
The development of a sustainable economy based on the use of renewable resources and the reduction of greenhouse gases emissions is an important mandate in modern societies to minimize the global warming. The CO2-reforming of methane through a conversion of CO
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The development of a sustainable economy based on the use of renewable resources and the reduction of greenhouse gases emissions is an important mandate in modern societies to minimize the global warming. The CO2-reforming of methane through a conversion of CO2 and CH4 to syngas is a suitable process for this purpose and there is growing interest in the development of new catalysts for this process’ application at an industrial scale. This study is the first to investigate methane dry reforming activity of nickel supported on CeO2 and CeO2–ZrO2 solid solutions doped with neodymium. The supports were synthesized using a surfactant-assisted co-precipitation method and characterized through several analytical techniques to understand the role of synthesis parameters in the distribution of the dopant as well as in the properties of the supports. Co-doping with Zr and Nd resulted in an enhancement of dry reforming activity of ceria due to a higher dispersion of Ni and changes in the strength of basic sites. It was also shown that the addition of Nd helped to mitigate coking issues by increasing the mobility of surface oxygen in ceria and ceria–zirconia oxides and, accordingly, the rate of oxidation of carbonaceous deposits. Full article
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Open AccessArticle
The Melt of Sodium Nitrate as a Medium for the Synthesis of Fluorides
Inorganics 2018, 6(2), 38; doi:10.3390/inorganics6020038 -
Abstract
The preparation of NaLnF4 complexes, LnF3 (Ln = La, Ce, Y) rare earth binary fluorides, CaF2 and SrF2 alkali earth fluorides, as well as mixtures of these compounds from their nitrates dissolved in molten NaNO3 has been studied
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The preparation of NaLnF4 complexes, LnF3 (Ln = La, Ce, Y) rare earth binary fluorides, CaF2 and SrF2 alkali earth fluorides, as well as mixtures of these compounds from their nitrates dissolved in molten NaNO3 has been studied in order to select the ideal solvent for fluoride synthesis by spontaneous crystallization from flux. Sodium fluoride (NaF) was used as a fluorinating agent. The results of our experiments have confirmed that NaNO3 melt is one of the most promising media for precipitating said inorganic fluoride materials within a broad temperature range (300–500 °С). Also, in contrast with precipitation/co-precipitation from aqueous solutions, our syntheses have resulted in obtaining equilibrium phases only. Full article
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Open AccessArticle
Computational Treatments of Hybrid Dye Materials of Azobenzene and Chiral Schiff Base Metal Complexes
Inorganics 2018, 6(2), 37; doi:10.3390/inorganics6020037 -
Abstract
Molecular orientation of dyes must be one of the important factors for designing dye-sensitized solar cells (DSSC). As model systems, we have prepared new hybrid materials composed of azobenzene (AZ) and chiral Schiff base Cu(II) complexes (pn(S)Cu and
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Molecular orientation of dyes must be one of the important factors for designing dye-sensitized solar cells (DSSC). As model systems, we have prepared new hybrid materials composed of azobenzene (AZ) and chiral Schiff base Cu(II) complexes (pn(S)Cu and pn(R)Cu) in polymethyl methacrylate (PMMA) cast films. In addition to experimental results, in order to understand their behavior due to anisotropic alignment of them by linearly polarized UV light irradiation, the so-called Weigert effect, we treated theoretically and discussed based on computational chemistry and mathematical treatments (MD simulation and Bayesian statistics). Full article
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Open AccessArticle
The Exploration and Analysis of the Magnetic Relaxation Behavior in Three Isostructural Cyano-Bridged 3d–4f Linear Heterotrinuclear Compounds
Inorganics 2018, 6(2), 36; doi:10.3390/inorganics6020036 -
Abstract
Three isostructural cyano-bridged 3d–4f linear heterotrinuclear compounds, (H2.5O)4{Ln[TM(CN)5(CNH0.5)]2(HMPA)4} (Ln = YIII, TM = [FeIII]LS (1); Ln = DyIII, TM = [FeIII
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Three isostructural cyano-bridged 3d–4f linear heterotrinuclear compounds, (H2.5O)4{Ln[TM(CN)5(CNH0.5)]2(HMPA)4} (Ln = YIII, TM = [FeIII]LS (1); Ln = DyIII, TM = [FeIII]LS (2); Ln = DyIII, TM = CoIII (3)), have been synthesized and characterized by single-crystal X-ray diffraction. Due to the steric effect of the HMPA ligands, the central lanthanide ions in these compounds possess a low coordination number, six-coordinate, exhibiting a coordination geometry of an axially elongated octahedron with a perfect D4h symmetry. Four HMPA ligands situate in the equatorial plane around the central lanthanide ions, and two [TM(CN)5(CNH0.5)]2.5− entities occupy the apical positions to form a cyano-bridged 3d–4f linear heterotrinuclear structure. The static magnetic analysis of the three compounds indicated a paramagnetic behavior of compounds 1 and 3, and possible small magnetic interactions between the intramolecular DyIII and [FeIII]LS ions in compound 2. Under zero dc field, the ac magnetic measurements on 2 and 3 revealed the in-phase component (χ′) of the ac susceptibility without frequency dependence and silent out-of-phase component (χ″), which was attributed to the QTM effect induced by the coordination geometry of an axially elongated octahedron for the DyIII ion. Even under a 1 kOe applied dc field, the χ″ components of 2 were revealed frequency dependence without peaks above 2 K. And under a 2 kOe and 3 kOe dc field, the χ″ components of 3 exhibited weak frequency dependence below 4 K with the absence of well-shaped peaks, which confirmed the poor single-ion magnetic relaxation behavior of the six-coordinate DyIII ion excluding any influence from the neighboring [FeIII]LS ions as that in the analogue 2. Full article
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Open AccessArticle
Field-Induced Slow Relaxation in a Dinuclear Dysprosium(III) Complex Based on 3-Methoxycinnamic Acid
Inorganics 2018, 6(1), 35; doi:10.3390/inorganics6010035 -
Abstract
We report the synthesis, structure, and magnetic properties of a new dinuclear dysprosium(III) complex based on a 3-methoxycinnamate ligand. The centrosymmetric complex exhibits a field-induced SMM behavior. In contrast to the previously reported lanthanide-based systems with cinnamate derivatives that relax through a combination
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We report the synthesis, structure, and magnetic properties of a new dinuclear dysprosium(III) complex based on a 3-methoxycinnamate ligand. The centrosymmetric complex exhibits a field-induced SMM behavior. In contrast to the previously reported lanthanide-based systems with cinnamate derivatives that relax through a combination of Raman and direct processes, an Orbach process is also involved in highlighting the role of the structural organization over the spin-lattice relaxations. Full article
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Open AccessReview
Atomic Layer Deposition on Porous Materials: Problems with Conventional Approaches to Catalyst and Fuel Cell Electrode Preparation
Inorganics 2018, 6(1), 34; doi:10.3390/inorganics6010034 -
Abstract
Atomic layer deposition (ALD) offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC) electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces,
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Atomic layer deposition (ALD) offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC) electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces, the conditions required for ALD in porous materials with a large surface area need to be very different. The materials (e.g., rare earths and other functional oxides) that are of interest for catalytic applications will also be different. For flat surfaces, rapid cycling, enabled by high carrier-gas flow rates, is necessary in order to rapidly grow thicker films. By contrast, ALD films in porous materials rarely need to be more than 1 nm thick. The elimination of diffusion gradients, efficient use of precursors, and ligand removal with less reactive precursors are the major factors that need to be controlled. In this review, criteria will be outlined for the successful use of ALD in porous materials. Examples of opportunities for using ALD to modify heterogeneous catalysts and SOFC electrodes will be given. Full article
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Open AccessArticle
Reaction of Non-Symmetric Schiff Base Metallo-Ligand Complexes Possessing an Oxime Function with Ln Ions
Inorganics 2018, 6(1), 33; doi:10.3390/inorganics6010033 -
Abstract
The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral
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The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral non-symmetric CuII or NiII metallo-ligand complexes under their mono- or di-deprotonated forms. In presence of Lanthanide ions the neutral complexes do not coordinate to the LnIII ions, the oxygen atom of the oxime function being only hydrogen-bonded to a water molecule that is linked to the LnIII ion. This surprising behavior allows for the isolation of LnIII ions by non-interacting metal complexes. Reaction of cationic NiII complexes possessing a protonated oxime function with LnIII ions leads to the formation of original and dianionic (Gd(NO3)5)2− entities that are well separated from each other. This work highlights the preparation of well isolated mononuclear LnIII entities into a matrix of diamagnetic metal complexes. These new complexes complete our previous work dealing with the complexing ability of the oxime function toward Lanthanide ions. It could open the way to the synthesis of new entities with interesting properties, such as single-ion magnets for example. Full article
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Open AccessEditorial
Spin-Crossover Complexes
Inorganics 2018, 6(1), 32; doi:10.3390/inorganics6010032 -
Abstract
Spin-crossover (SCO) is a spin-state switching phenomenon between a high-spin (HS) and low-spin (LS) electronic configurations in a transition metal center. Full article
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Open AccessArticle
Predicted Siliconoids by Bridging Si9 Clusters through sp3-Si Linkers
Inorganics 2018, 6(1), 31; doi:10.3390/inorganics6010031 -
Abstract
Charged and neutral silicon clusters comprising Si atoms that are exclusively connected to atoms of the same type serve as models for bulk silicon surfaces. The experimentally known nido-[Si9]4− Zintl cluster is investigated as a building block and allows
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Charged and neutral silicon clusters comprising Si atoms that are exclusively connected to atoms of the same type serve as models for bulk silicon surfaces. The experimentally known nido-[Si9]4− Zintl cluster is investigated as a building block and allows for a theoretical prediction of novel silicon-rich oligomers and polymers by interconnection of such building units to larger aggregates. The stability and electronic properties of the polymers {([Si9](SiCl2)2)1n} and {([Si9](SiH2)2)1n}, as well as of related oligomers are presented. Full article
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Open AccessArticle
Synthesis and Characterization of N-Heterocyclic Carbene-Coordinated Silicon Compounds Bearing a Fused-Ring Bulky Eind Group
Inorganics 2018, 6(1), 30; doi:10.3390/inorganics6010030 -
Abstract
The reactions of the fused-ring bulky Eind-substituted 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (a)), with N-heterocyclic carbenes (NHCs) (Im-Me4 = 1,3,4,5-tetramethylimidazol-2-ylidene and Im-iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) are reported. While the reaction
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The reactions of the fused-ring bulky Eind-substituted 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (a)), with N-heterocyclic carbenes (NHCs) (Im-Me4 = 1,3,4,5-tetramethylimidazol-2-ylidene and Im-iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) are reported. While the reaction of 1a with the sterically more demanding Im-iPr2Me2 led to the formation of the mono-NHC adduct of arylbromosilylene, (Im-iPr2Me2)→SiBr(Eind) (2a′), a similar reaction using the less bulky Im-Me4 affords the bis-NHC adduct of formal arylsilyliumylidene cation, [(Im-Me4)2→Si(Eind)]+[Br] (3a). The NHC adducts 2a′ and 3a can also be prepared by the dehydrobromination of Eind-substituted dibromohydrosilane, (Eind)SiHBr2 (4a), with NHCs. The NHC-coordinated silicon compounds have been characterized by spectroscopic methods. The molecular structures of bis-NHC adduct, [(Im-iPr2Me2)2→Si(Eind)]+[Br] (3a′), and 4a have been determined by X-ray crystallography. Full article
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Open AccessArticle
Synthesis Target Structures for Alkaline Earth Oxide Clusters
Inorganics 2018, 6(1), 29; doi:10.3390/inorganics6010029 -
Abstract
Knowing the possible structures of individual clusters in nanostructured materials is an important first step in their design. With previous structure prediction data for BaO nanoclusters as a basis, data mining techniques were used to investigate candidate structures for magnesium oxide, calcium oxide
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Knowing the possible structures of individual clusters in nanostructured materials is an important first step in their design. With previous structure prediction data for BaO nanoclusters as a basis, data mining techniques were used to investigate candidate structures for magnesium oxide, calcium oxide and strontium oxide clusters. The lowest-energy structures and analysis of some of their structural properties are presented here. Clusters that are predicted to be ideal targets for synthesis, based on being both the only thermally accessible minimum for their size, and a size that is thermally accessible with respect to neighbouring sizes, include global minima for: sizes n=9,15,16,18 and 24 for (MgO)n; sizes n=8,9,12,16,18 and 24 for (CaO)n; the greatest number of sizes of (SrO)n clusters (n=8,9,10,12,13,15,16,18 and 24); and for (BaO)n sizes of n=8,10 and 16. Full article
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Open AccessArticle
Probing the Effect of Six-Membered N-Heterocyclic Carbene—6-Mes—on the Synthesis, Structure and Reactivity of Me2MOR(NHC) (M = Ga, In) Complexes
Inorganics 2018, 6(1), 28; doi:10.3390/inorganics6010028 -
Abstract
The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure
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The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes) (M = Ga, In) complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe)(6-Mes) (1) and Me2GaOMe(6-Mes) complexes, the analogous Me2InOR(6-Mes) are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes) (2). The use of bulky alkoxide ligand—OCPh2Me or aryloxide ligand—OC6H4OMe allowed for the synthesis of stable Me2M(OCPh2Me)(6-Mes) (M = Ga (3) and In (4)) as well as Me2M(OC6H4OMe)(6-Mes) (M = Ga (5) and In (6)). The structures of 16 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP) of rac-lactide. Full article
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Open AccessArticle
Cationic Protic Imidazolylidene NHC Complexes of Cp*IrCl+ and Cp*RhCl+ with a Pyridyl Tether Formed at Ambient Temperature
Inorganics 2018, 6(1), 27; doi:10.3390/inorganics6010027 -
Abstract
Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of
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Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of a tethering ligand (phosphine or in one case, pyridine), CpM and Cp*M (M = Ir, Ru) PNHC complexes could be made by heating. Here, we find that the use of ionizing agents to activate [Cp*MIIICl(μ-Cl)]2 (M = Ir, Rh) allows for what we believe is unprecedented ambient temperature formation of PNHC complexes from neutral imidazoles; the product complexes are able to perform transfer hydrogenation. Full article
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Open AccessReview
Future Directions for Transuranic Single Molecule Magnets
Inorganics 2018, 6(1), 26; doi:10.3390/inorganics6010026 -
Abstract
Single Molecule Magnets (SMMs) based on transition metals and rare earths have been the object of considerable attention for the past 25 years. These systems exhibit slow relaxation of the magnetization, arising from a sizeable anisotropy barrier, and magnetic hysteresis of purely molecular
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Single Molecule Magnets (SMMs) based on transition metals and rare earths have been the object of considerable attention for the past 25 years. These systems exhibit slow relaxation of the magnetization, arising from a sizeable anisotropy barrier, and magnetic hysteresis of purely molecular origin below a given blocking temperature. Despite initial predictions that SMMs based on 5f-block elements could outperform most others, the results obtained so far have not met expectations. Exploiting the versatile chemistry of actinides and their favorable intrinsic magnetic properties proved, indeed, to be more difficult than assumed. However, the large majority of studies reported so far have been dedicated to uranium molecules, thus leaving the largest part of the 5f-block practically unexplored. Here, we present a short review of the progress achieved up to now and discuss some options for a possible way forward. Full article
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Open AccessReview
The Fe Protein: An Unsung Hero of Nitrogenase
Inorganics 2018, 6(1), 25; doi:10.3390/inorganics6010025 -
Abstract
Although the nitrogen-fixing enzyme nitrogenase critically requires both a reductase component (Fe protein) and a catalytic component, considerably more work has focused on the latter species. Properties of the catalytic component, which contains two highly complex metallocofactors and catalyzes the reduction of N
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Although the nitrogen-fixing enzyme nitrogenase critically requires both a reductase component (Fe protein) and a catalytic component, considerably more work has focused on the latter species. Properties of the catalytic component, which contains two highly complex metallocofactors and catalyzes the reduction of N2 into ammonia, understandably making it the “star” of nitrogenase. However, as its obligate redox partner, the Fe protein is a workhorse with multiple supporting roles in both cofactor maturation and catalysis. In particular, the nitrogenase Fe protein utilizes nucleotide binding and hydrolysis in concert with electron transfer to accomplish several tasks of critical importance. Aside from the ATP-coupled transfer of electrons to the catalytic component during substrate reduction, the Fe protein also functions in a maturase and insertase capacity to facilitate the biosynthesis of the two-catalytic component metallocofactors: fusion of the [Fe8S7] P-cluster and insertion of Mo and homocitrate to form the matured [(homocitrate)MoFe7S9C] M-cluster. These and key structural-functional relationships of the indispensable Fe protein and its complex with the catalytic component will be covered in this review. Full article
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Open AccessArticle
Effect of Low Spin Excited States for Magnetic Anisotropy of Transition Metal Mononuclear Single Molecule Magnets
Inorganics 2018, 6(1), 24; doi:10.3390/inorganics6010024 -
Abstract
Rational, fine tuning of magnetic anisotropy is critical to obtain new coordination compounds with enhanced single molecule magnet properties. For mononuclear transition metal complexes, the largest contribution to zero-field splitting is usually related to the excited states of the same spin as the
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Rational, fine tuning of magnetic anisotropy is critical to obtain new coordination compounds with enhanced single molecule magnet properties. For mononuclear transition metal complexes, the largest contribution to zero-field splitting is usually related to the excited states of the same spin as the ground level. Thus, the contribution of lower multiplicity roots tends to be overlooked due to its lower magnitude. In this article, we explore the role of lower multiplicity excited states in zero-field splitting parameters in model structures of Fe(II) and Co(II). Model aquo complexes with coordination numbers ranging from 2 to 6 were constructed. The magnetic anisotropy was calculated by state of the art ab initio methodologies, including spin-orbit coupling effects. For non-degenerate ground states, contributions to the zero-field splitting parameter (D) from highest and lower multiplicity roots were of the same sign. In addition, their relative magnitude was in a relatively narrow range, irrespective of the coordination geometry. For degenerate ground states, the contribution from lower multiplicity roots was significantly smaller. Results are rationalized in terms of general expressions for D and are expected to be reasonably transferable to real molecular systems. Full article
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Open AccessArticle
Sterically Bulky NHC Adducts of GaMe3 and InMe3 for H2 Activation and Lactide Polymerization
Inorganics 2018, 6(1), 23; doi:10.3390/inorganics6010023 -
Abstract
The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized,
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The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized, allowing an estimation of the steric hindrance of such Lewis pairs (yields in 14: 92%, 90%, 73%, and 42%, respectively). While the IPr* adducts 1 and 2 are robust species, the more severely congested SItBu adducts 3 and 4 are more reactive and exhibit a limited stability in solution. Adduct (SItBu)GaMe3 (3) reacts quickly with H2 at room temperature to afford the corresponding aminal product, 1,3-di-tert-butylimidazolidine (5), along with free GaMe3. Such Frustrated Lewis Pair (FLP) reactivity constitutes the first instance of a H2 activation involving a simple trialkyl GaR3 species. Adduct 3 also mediates the ring-opening polymerization (ROP) of rac-lactide at room temperature to afford cyclic polylactide (PLA). Full article
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