Open AccessArticle
[Bis(Trimethylsilyl)Methyl]Lithium and -Sodium: Solubility in Alkanes and Complexes with O- and N- Donor Ligands
Inorganics 2017, 5(2), 39; doi:10.3390/inorganics5020039 -
Abstract
In contrast to alkyl compounds of lithium, which play an important role in organometallic chemistry, the corresponding heavier alkali metal compounds are less investigated. These compounds are mostly insoluble in inert solvents or undergo solvolysis in coordinating solvents due to their high reactivity.
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In contrast to alkyl compounds of lithium, which play an important role in organometallic chemistry, the corresponding heavier alkali metal compounds are less investigated. These compounds are mostly insoluble in inert solvents or undergo solvolysis in coordinating solvents due to their high reactivity. An exception from this typical behavior is demonstrated by bis(trimethylsilyl)methylsodium. This study examines alkane solutions of bis(trimethylsilyl)methyllithium and -sodium by NMR spectroscopic and cryoscopic methods. In addition, structural studies by X-ray crystallography of the corresponding compounds coordinated by O- and N- ligands (tetrahydrofuran and tetramethylethylenediamine) present possible structural motifs of the uncoordinated compounds in solution. Full article
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Open AccessArticle
Synthesis of LiAlH4 Nanoparticles Leading to a Single Hydrogen Release Step upon Ti Coating
Inorganics 2017, 5(2), 38; doi:10.3390/inorganics5020038 -
Abstract
Lithium aluminum hydride (LiAlH4) is an interesting high capacity hydrogen storage material with fast hydrogen release kinetics when mechanically activated with additives. Herein, we report on a novel approach to produce nanoscale LiAlH4 via a bottom-up synthesis. Upon further coating
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Lithium aluminum hydride (LiAlH4) is an interesting high capacity hydrogen storage material with fast hydrogen release kinetics when mechanically activated with additives. Herein, we report on a novel approach to produce nanoscale LiAlH4 via a bottom-up synthesis. Upon further coating of these nanoparticles with Ti, the composite nanomaterial was found to decompose at 120 °C in one single and extremely sharp exothermic event with instant hydrogen release. This finding implies a significant thermodynamic alteration of the hydrogen properties of LiAlH4 induced by the synergetic effects of the Ti catalytic coating and nanosizing effects. Ultimately, the decomposition path of LiAlH4 was changed to LiAlH4 → Al + LiH + 3/2H2. Full article
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Open AccessReview
First-Principles View on Photoelectrochemistry: Water-Splitting as Case Study
Inorganics 2017, 5(2), 37; doi:10.3390/inorganics5020037 -
Abstract
Photoelectrochemistry is truly an interdisciplinary field; a natural nexus between chemistry and physics. In short, photoelectrochemistry can be divided into three sub-processes, namely (i) the creation of electron-hole pairs by light absorption; (ii) separation/transport on the charge carriers and finally (iii) the water
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Photoelectrochemistry is truly an interdisciplinary field; a natural nexus between chemistry and physics. In short, photoelectrochemistry can be divided into three sub-processes, namely (i) the creation of electron-hole pairs by light absorption; (ii) separation/transport on the charge carriers and finally (iii) the water splitting reaction. The challenge is to understand all three processes on a microscopic scale and, perhaps even more importantly, how to combine the processes in an optimal way. This review will highlight some first-principles insights to the above sub-processes, in~particular as they occur using metal oxides. Based on these insights, challenges and future directions of first-principles methods in the field of photoelectrochemistry will be discussed. Full article
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Open AccessArticle
Symmetric Assembly of a Sterically Encumbered Allyl Complex: Mechanochemical and Solution Synthesis of the Tris(allyl)beryllate, K[BeA′3] (A′ = 1,3-(SiMe3)2C3H3)
Inorganics 2017, 5(2), 36; doi:10.3390/inorganics5020036 -
Abstract
The ball milling of beryllium chloride with two equivalents of the potassium salt of bis(1,3-trimethylsilyl)allyl anion, K[A′] (A′ = [1,3-(SiMe3)2C3H3]), produces the tris(allyl)beryllate K[BeA’3] (1) rather than the expected neutral BeA’
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The ball milling of beryllium chloride with two equivalents of the potassium salt of bis(1,3-trimethylsilyl)allyl anion, K[A′] (A′ = [1,3-(SiMe3)2C3H3]), produces the tris(allyl)beryllate K[BeA’3] (1) rather than the expected neutral BeA’2. The same product is obtained from reaction in hexanes; in contrast, although a similar reaction conducted in Et2O was previously shown to produce the solvated species BeA’2(OEt2), it can produce 1 if the reaction time is extended (16 h). The tris(allyl)beryllate is fluxional in solution, and displays the strongly downfield 9Be NMR shift expected for a three-coordinate Be center (δ22.8 ppm). A single crystal X-ray structure reveals that the three allyl ligands are bound to beryllium in an arrangement with approximate C3 symmetry (Be–C (avg) = 1.805(10) Å), with the potassium cation engaging in cation–π interactions with the double bonds of the allyl ligands. Similar structures have previously been found in complexes of zinc and tin, i.e., M[M′A′3L] (M′ = Zn, M = Li, Na, K; M′ = Sn, M = K; L = thf). Density functional theory (DFT) calculations indicate that the observed C3-symmetric framework of the isolated anion ([BeA′3]) is 20 kJ·mol−1 higher in energy than a C1 arrangement; the K+ counterion evidently plays a critical role in templating the final conformation. Full article
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Open AccessReview
Product Selectivity in Homogeneous Artificial Photosynthesis Using [(bpy)Rh(Cp*)X]n+-Based Catalysts
Inorganics 2017, 5(2), 35; doi:10.3390/inorganics5020035 -
Abstract
Due to the limited amount of fossil energy carriers, the storage of solar energy in chemical bonds using artificial photosynthesis has been under intensive investigation within the last decades. As the understanding of the underlying working principle of these complex systems continuously grows,
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Due to the limited amount of fossil energy carriers, the storage of solar energy in chemical bonds using artificial photosynthesis has been under intensive investigation within the last decades. As the understanding of the underlying working principle of these complex systems continuously grows, more focus will be placed on a catalyst design for highly selective product formation. Recent reports have shown that multifunctional photocatalysts can operate with high chemoselectivity, forming different catalysis products under appropriate reaction conditions. Within this context [(bpy)Rh(Cp*)X]n+-based catalysts are highly relevant examples for a detailed understanding of product selectivity in artificial photosynthesis since the identification of a number of possible reaction intermediates has already been achieved. Full article
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Open AccessReview
Dye-Sensitized Photocatalytic Water Splitting and Sacrificial Hydrogen Generation: Current Status and Future Prospects
Inorganics 2017, 5(2), 34; doi:10.3390/inorganics5020034 -
Abstract
Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting
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Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting and sacrificial hydrogen generation show a promise for future energy generation from renewable water and sunlight. This article mainly reviews the current research progress on photocatalytic and photo-electrochemical systems focusing on dye-sensitized overall water splitting and sacrificial hydrogen generation. An overview of significant parameters including dyes, sacrificial agents, modified photocatalysts and co-catalysts are provided. Also, the significance of statistical analysis as an effective tool for a systematic investigation of the effects of different factors and their interactions are explained. Finally, different photocatalytic reactor configurations that are currently in use for water splitting application in laboratory and large scale are discussed. Full article
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Open AccessArticle
Hetero- and Homoleptic Magnesium Triazenides
Inorganics 2017, 5(2), 33; doi:10.3390/inorganics5020033 -
Abstract
Using monoanionic triazenide ligands derived from biphenyl and m-terphenyl substituted triazenes Dmp(Tph)N3H (1a), (Me4Ter)2N3H (1b) or Dmp(Mph)N3H (1c) (Dmp = 2,6-Mes2C6H3 with Mes = 2,4,6-Me3C6H2; Me4Ter = 2,6-(3,5-Me2C6H3)2C6H3; Mph = 2-MesC6H4; Tph = 2-TripC6H4 with Trip = 2,4,6-i-Pr3C6H2), several magnesium triazenides were synthesized.
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Using monoanionic triazenide ligands derived from biphenyl and m-terphenyl substituted triazenes Dmp(Tph)N3H (1a), (Me4Ter)2N3H (1b) or Dmp(Mph)N3H (1c) (Dmp = 2,6-Mes2C6H3 with Mes = 2,4,6-Me3C6H2; Me4Ter = 2,6-(3,5-Me2C6H3)2C6H3; Mph = 2-MesC6H4; Tph = 2-TripC6H4 with Trip = 2,4,6-i-Pr3C6H2), several magnesium triazenides were synthesized. Heteroleptic complexes [Mg(N3Ar2)I(OEt2)] (Ar2 = Dmp/Tph (2a), (Me4Ter)2 (2b) were obtained from metalation of the corresponding triazenes with di-n-butylmagnesium followed by reaction with iodine in diethyl ether as the solvent in high yields. Replacing diethyl ether by n-heptane afforded trinuclear compounds [Mg3(N3Ar2)2I4] (3a, 3b) in low yields in which a central MgI2 fragment is coordinated by two iodomagnesium triazenide moieties. Two unsolvated homoleptic magnesium compounds [Mg(N3Ar2)2] (4b, 4c) were obtained from di-n-butylmagnesium and triazenes 1b or 1c in a 1:2 ratio. Depending on the nature of the substituents, the magnesium center either shows the expected tetrahedral or a rather unusual square planar coordination. Full article
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Open AccessReview
Study of Cathode Materials for Lithium-Ion Batteries: Recent Progress and New Challenges
Inorganics 2017, 5(2), 32; doi:10.3390/inorganics5020032 -
Abstract
Amongst a number of different cathode materials, the layered nickel-rich LiNiyCoxMn1−yxO2 and the integrated lithium-rich xLi2MnO3·(1 − x)Li[NiaCobMnc]O2 (a
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Amongst a number of different cathode materials, the layered nickel-rich LiNiyCoxMn1−yxO2 and the integrated lithium-rich xLi2MnO3·(1 − x)Li[NiaCobMnc]O2 (a + b + c = 1) have received considerable attention over the last decade due to their high capacities of ~195 and ~250 mAh·g−1, respectively. Both materials are believed to play a vital role in the development of future electric vehicles, which makes them highly attractive for researchers from academia and industry alike. The review at hand deals with both cathode materials and highlights recent achievements to enhance capacity stability, voltage stability, and rate capability, etc. The focus of this paper is on novel strategies and established methods such as coatings and dopings. Full article
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Open AccessArticle
Backbone-Substituted β-Ketoimines and Ketoiminate Clusters: Transoid Li2O2 Squares and D2-Symmetric Li4O4 Cubanes. Synthesis, Crystallography and DFT Calculations
Inorganics 2017, 5(2), 30; doi:10.3390/inorganics5020030 -
Abstract
The preparation and crystal structures of four β-ketoimines with bulky aryl nitrogen substituents (2,6-diisopropylphenyl and 2,4,6-trimethylphenyl) and varying degrees of backbone methyl substitution are reported. Backbone substitution “pinches” the chelate ring. Deprotonation with n-butyllithium leads to dimeric Li2O2 clusters,
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The preparation and crystal structures of four β-ketoimines with bulky aryl nitrogen substituents (2,6-diisopropylphenyl and 2,4,6-trimethylphenyl) and varying degrees of backbone methyl substitution are reported. Backbone substitution “pinches” the chelate ring. Deprotonation with n-butyllithium leads to dimeric Li2O2 clusters, as primary laddered units, with an open transoid geometry as shown by crystal structures of three examples. The coordination sphere of each lithium is completed by one tetrahydrofuran ligand. NMR spectra undertaken in either C6D6 or 1:1 C6D6/d8-THF show free THF in solution and the chemical shifts of ligand methyl groups experience significant ring-shielding which can only occur from aryl rings on adjacent ligands. Both features point to conversion to higher-order aggregates when the THF concentration is reduced. Recrystallization of the materials from hydrocarbon solutions results in secondary laddering as tetrameric Li4O4 clusters with a cuboidal core, three examples of which have been crystallographically characterised. These clusters are relatively insoluble and melt up to 250 °C; a consideration of the solid-state structures indicates that the clusters with 2,6-diisopropylphenyl substituents form very uniform ball-like molecular structures that will only be weakly solvated. Full article
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Open AccessArticle
Hydrogen Sorption in Erbium Borohydride Composite Mixtures with LiBH4 and/or LiH
Inorganics 2017, 5(2), 31; doi:10.3390/inorganics5020031 -
Abstract
Rare earth (RE) metal borohydrides have recently been receiving attention as possible hydrogen storage materials and solid-state Li-ion conductors. In this paper, the decomposition and reabsorption of Er(BH4)3 in composite mixtures with LiBH4 and/or LiH were investigated. The composite
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Rare earth (RE) metal borohydrides have recently been receiving attention as possible hydrogen storage materials and solid-state Li-ion conductors. In this paper, the decomposition and reabsorption of Er(BH4)3 in composite mixtures with LiBH4 and/or LiH were investigated. The composite of 3LiBH4 + Er(BH4)3 + 3LiH has a theoretical hydrogen storage capacity of 9 wt %, nevertheless, only 6 wt % hydrogen are accessible due to the formation of thermally stable LiH. Hydrogen sorption measurements in a Sieverts-type apparatus revealed that during three desorption-absorption cycles of 3LiBH4 + Er(BH4)3 + 3LiH, the composite desorbed 4.2, 3.7 and 3.5 wt % H for the first, second and third cycle, respectively, and thus showed good rehydrogenation behavior. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) after ball milling of Er(BH4)3 + 6LiH resulted in the formation of LiBH4, revealing that metathesis reactions occurred during milling in these systems. Impedance spectroscopy of absorbed Er(BH4)3 + 6LiH showed an exceptional high hysteresis of 40–60 K for the transition between the high and low temperature phases of LiBH4, indicating that the high temperature phase of LiBH4 is stabilized in the composite. Full article
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Open AccessArticle
Methanediide Formation via Hydrogen Elimination in Magnesium versus Aluminium Hydride Complexes of a Sterically Demanding Bis(iminophosphoranyl)methanediide
Inorganics 2017, 5(2), 29; doi:10.3390/inorganics5020029 -
Abstract
Substituted bis(iminophosphoranyl)methanes are CH acidic compounds that can form complexes with formally dianionic central carbon centres. The reaction of H2C(Ph2P=NDip)2 (≡ H2L), Dip = 2,6-diisopropylphenyl, with one equivalent of di-n-butylmagnesium afforded the methanide complex
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Substituted bis(iminophosphoranyl)methanes are CH acidic compounds that can form complexes with formally dianionic central carbon centres. The reaction of H2C(Ph2P=NDip)2 (≡ H2L), Dip = 2,6-diisopropylphenyl, with one equivalent of di-n-butylmagnesium afforded the methanide complex [HLMgnBu] 1. Treatment of Complex 1 with phenylsilane in aromatic solvents at elevated temperatures afforded the methanediide complex [(LMg)2] 2 presumably via the MgH intermediate [(HLMgH)n] (n = 1 or 2). The reaction of 1 with LiAlH4 in diethyl ether yielded the AlH complex [HLAlH2] 3. Alternatively, this complex was also obtained from the reaction of H2L with AlH3∙NMe3. The molecular structures of [HLMgnBu] 1, [(LMg)2] 2, and [HLAlH2] 3 are reported. Complex 3 shows no sign of H2 elimination to a methanediide species at elevated temperatures in contrast to the facile elimination of the putative reaction intermediate [(HLMgH)n] (n = 1 or 2) to form [(LMg)2] 2. The chemical properties of Complex 2 were investigated, and this complex appears to be stable against coordination with strong donor molecules. Full article
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Open AccessArticle
Pulsed Current Electrodeposition of Silicon Thin Films Anodes for Lithium Ion Battery Applications
Inorganics 2017, 5(2), 27; doi:10.3390/inorganics5020027 -
Abstract
Electrodeposition of amorphous silicon thin films on Cu substrate from organic ionic electrolyte using pulsed electrodeposition conditions has been studied. Scanning electron microscopy analysis shows a drastic change in the morphology of these electrodeposited silicon thin films at different frequencies of 0, 500,
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Electrodeposition of amorphous silicon thin films on Cu substrate from organic ionic electrolyte using pulsed electrodeposition conditions has been studied. Scanning electron microscopy analysis shows a drastic change in the morphology of these electrodeposited silicon thin films at different frequencies of 0, 500, 1000, and 5000 Hz studied due to the change in nucleation and the growth mechanisms. These electrodeposited films, when tested in a lithium ion battery configuration, showed improvement in stability and performance with an increase in pulse current frequency during deposition. XPS analysis showed variation in the content of Si and oxygen with the change in frequency of deposition and with the change in depth of these thin films. The presence of oxygen largely due to electrolyte decomposition during Si electrodeposition and the structural instability of these films during the first discharge–charge cycle are the primary reasons contributing to the first cycle irreversible (FIR) loss observed in the pulse electrodeposited Si–O–C thin films. Nevertheless, the silicon thin films electrodeposited at a pulse current frequency of 5000 Hz show a stable capacity of ~805 mAh·g−1 with a fade in capacity of ~0.056% capacity loss per cycle (a total loss of capacity ~246 mAh·g−1) at the end of 500 cycles. Full article
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Open AccessArticle
Alkali and Alkaline Earth Metal Complexes Ligated by an Ethynyl Substituted Cyclopentadienyl Ligand
Inorganics 2017, 5(2), 28; doi:10.3390/inorganics5020028 -
Abstract
Sodium, potassium, and calcium compounds of trimethyl((2,3,4,5-tetramethylcyclopentadien-1-yl)ethynyl)silane (CpMe4(C≡CSiMe3)) were synthesized and characterized by X-ray diffraction and standard analytical methods. The sodium derivative was obtained by deprotonation of CpMe4(C≡CSiMe3)H with Na{N(SiMe3)2} to
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Sodium, potassium, and calcium compounds of trimethyl((2,3,4,5-tetramethylcyclopentadien-1-yl)ethynyl)silane (CpMe4(C≡CSiMe3)) were synthesized and characterized by X-ray diffraction and standard analytical methods. The sodium derivative was obtained by deprotonation of CpMe4(C≡CSiMe3)H with Na{N(SiMe3)2} to give a monomeric complex [NaCpMe4(C≡CSiMe3)(THF)3]. In a similar reaction, starting from K{N(SiMe3)2} the corresponding potassium compound [KCpMe4(C≡CSiMe3)(THF)2]n, which forms a polymeric super sandwich structure in the solid state, was obtained. Subsequently, salt metathesis reactions were conducted in order to investigate the versatility of the CpMe4(C≡CSiMe3) ligand in alkaline earth chemistry. The reaction of [KCpMe4(C≡CSiMe3)(THF)2]n with CaI2 afforded the dimeric complex [CaCpMe4(C≡CSiMe3)I(THF)2]2, in which both CpMe4(C≡CSiMe3)Ca units are bridged by iodide in a μ2 fashion. In-depth NMR investigation indicates that [CaCpMe4(C≡CSiMe3)I(THF)2]2 is in a Schlenk equilibrium with [{CpMe4(C≡CSiMe3)}2Ca(THF)x] and CaI2(THF)2, as is already known for [CaCp*I(THF)2]. Full article
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Open AccessArticle
Potassium C–F Interactions and the Structural Consequences in N,N′-Bis(2,6-difluorophenyl)formamidinate Complexes
Inorganics 2017, 5(2), 26; doi:10.3390/inorganics5020026 -
Abstract
Treatment of K[N(SiMe3)2] with N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) in toluene, resulted in the formation of [K(DFForm)]∞ (1) as a poorly soluble material. Upon dissolution in thf and layering with n-hexane, 1 was crystallised and identified as a two-dimensional polymer, in which all fluorine and nitrogen
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Treatment of K[N(SiMe3)2] with N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) in toluene, resulted in the formation of [K(DFForm)]∞ (1) as a poorly soluble material. Upon dissolution in thf and layering with n-hexane, 1 was crystallised and identified as a two-dimensional polymer, in which all fluorine and nitrogen atoms, and also part of one aryl group, bridge between four symmetry equivalent potassium ions, giving rise to a completely unique μ4-(N,N′,F,F′):(N,N′):η4(Ar-C(2,3,4,5,6)):(F″,F′′′) DFForm coordination. The two-dimensional nature of the polymer could be deconstructed to one dimension by crystallisation from neat thf at −35 °C, giving [K2(DFForm)2(thf)2]∞ (2), where the thf molecules bridge the monomeric units. Complete polymer dissociation was observed when 1 was crystallised from toluene/n-hexane mixtures in the presence of 18-crown-6, giving [K(DFForm)(18-crown-6)] (3), which showed unprecedented κ(N,Cispo,F) DFForm coordination, rather than the expected κ(N,N′) coordination. Full article
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Open AccessReview
Nanotechnology of Positive Electrodes for Li-Ion Batteries
Inorganics 2017, 5(2), 25; doi:10.3390/inorganics5020025 -
Abstract
This work presents the recent progress in nanostructured materials used as positive electrodes in Li-ion batteries (LIBs). Three classes of host lattices for lithium insertion are considered: transition-metal oxides V2O5, α-NaV2O5, α-MnO2, olivine-like
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This work presents the recent progress in nanostructured materials used as positive electrodes in Li-ion batteries (LIBs). Three classes of host lattices for lithium insertion are considered: transition-metal oxides V2O5, α-NaV2O5, α-MnO2, olivine-like LiFePO4, and layered compounds LiNi0.55Co0.45O2, LiNi1/3Mn1/3Co1/3O2 and Li2MnO3. First, a brief description of the preparation methods shows the advantage of a green process, i.e., environmentally friendliness wet chemistry, in which the synthesis route using single and mixed chelators is used. The impact of nanostructure and nano-morphology of cathode material on their electrochemical performance is investigated to determine the synthesis conditions to obtain the best electrochemical performance of LIBs. Full article
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Open AccessReview
Visible Light-Activated PhotoCORMs
Inorganics 2017, 5(2), 24; doi:10.3390/inorganics5020024 -
Abstract
Despite its well-known toxicity, carbon monoxide (CO) is now recognized as a potential therapeutic agent. Its inherent toxicity, however, has limited clinical applications because uncontrolled inhalation of the gas leads to severe systemic derangements in higher organisms. In order to obviate life-threatening effects
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Despite its well-known toxicity, carbon monoxide (CO) is now recognized as a potential therapeutic agent. Its inherent toxicity, however, has limited clinical applications because uncontrolled inhalation of the gas leads to severe systemic derangements in higher organisms. In order to obviate life-threatening effects and administer the gas by bypassing the respiratory system, CO releasing molecules (CORMs) have emerged in the last decades as a plausible alternative to deliver controlled quantities of CO in cellular systems and tissues. As stable, solid-storage forms of CO, CORMs can be used to deliver the gas following activation by a stimulus. Light-activated CORMs, known as photoCORMs, are one such example. This class of molecules is particularly attractive because, for possible applications of CORMs, temporal and spatial control of CO delivery is highly desirable. However, systems triggered by visible light are rare. Most currently known photoCORMs are activated with UV light, but red light or even infrared photo-activation is required to ensure that structures deeper inside the body can be reached while minimizing photo-damage to healthy tissue. Thus, one of the most challenging chemical goals in the preparation of new photoCORMs is the reduction of radiation energy required for their activation, together with strategies to modulate the solubility, stability and nontoxicity of the organic or organometallic scaffolds. In this contribution, we review the latest advances in visible light-activated photoCORMs, and the first promising studies on near-infrared light activation of the same. Full article
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Open AccessArticle
Chemical Tuning and Absorption Properties of Iridium Photosensitizers for Photocatalytic Applications
Inorganics 2017, 5(2), 23; doi:10.3390/inorganics5020023 -
Abstract
Cyclometalated Ir(III) complexes are of particular interest due to the wide tunability of their electronic structure via variation of their ligands. Here, a series of heteroleptic Ir-based photosensitizers with the general formula [Ir(C^N)2(N^N)]+ has been studied theoretically by means of an optimally-tuned long-range
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Cyclometalated Ir(III) complexes are of particular interest due to the wide tunability of their electronic structure via variation of their ligands. Here, a series of heteroleptic Ir-based photosensitizers with the general formula [Ir(C^N)2(N^N)]+ has been studied theoretically by means of an optimally-tuned long-range separated density functional. Focusing on the steady-state absorption spectra, correlations between the chemical modification of both ligand types with the natures of the relevant dark and bright electronic states are revealed. Understanding such correlations builds up a basis for the rational design of efficient photocatalytic systems. Full article
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Open AccessArticle
Insights into Molecular Beryllium–Silicon Bonds
Inorganics 2017, 5(2), 22; doi:10.3390/inorganics5020022 -
Abstract
We present the synthesis of two silyl beryllium halides HypSiBeX∙(thf) (HypSi = Si(SiMe3)3, X = Cl 2a, I 4a) and the molecular structure of 2a as determined by single crystal X-ray diffraction. Compounds 2a and 4a were characterized via multi-nuclear NMR spectroscopy (1H,
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We present the synthesis of two silyl beryllium halides HypSiBeX∙(thf) (HypSi = Si(SiMe3)3, X = Cl 2a, I 4a) and the molecular structure of 2a as determined by single crystal X-ray diffraction. Compounds 2a and 4a were characterized via multi-nuclear NMR spectroscopy (1H, 9Be, 13C, 29Si), and the bonding situation was further investigated using quantum chemical calculations (with the addition of further halides X = F 1b, Cl 2b, Br 3b, I 4b). The nature of the beryllium silicon bond in the context of these compounds is highlighted and discussed. Full article
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Open AccessArticle
Photophysics of BODIPY Dyes as Readily-Designable Photosensitisers in Light-Driven Proton Reduction
Inorganics 2017, 5(2), 21; doi:10.3390/inorganics5020021 -
Abstract
A series of boron dipyrromethene (BODIPY) dyes was tested as photosensitisers for light-driven hydrogen evolution in combination with the complex [Pd(PPh3)Cl2]2 as a source for catalytically-active Pd nanoparticles and triethylamine as a sacrificial electron donor. In line with
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A series of boron dipyrromethene (BODIPY) dyes was tested as photosensitisers for light-driven hydrogen evolution in combination with the complex [Pd(PPh3)Cl2]2 as a source for catalytically-active Pd nanoparticles and triethylamine as a sacrificial electron donor. In line with earlier reports, halogenated dyes showed significantly higher hydrogen production activity. All BODIPYs were fully characterised using stationary absorption and emission spectroscopy. Time-resolved spectroscopic investigations on meso-mesityl substituted compounds revealed that reduction of the photo-excited BODIPY by the sacrificial agent occurs from an excited singlet state, while, in halogenated species, long-lived triplet states are present, determining electron transfer processes from the sacrificial agent. Quantum chemical calculations performed at the time-dependent density functional level of theory indicate that the differences in the photocatalytic performance of the present series of dyes can be correlated to the varying efficiency of intersystem crossing in non-halogenated and halogenated species and not to alterations in the energy levels introduced upon substitution. Full article
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Open AccessArticle
Investigation of the Structures and Energy Landscapes of Thiocyanate-Water Clusters
Inorganics 2017, 5(2), 20; doi:10.3390/inorganics5020020 -
Abstract
The Basin Hopping search method is used to find the global minima (GM) and map the energy landscapes of thiocyanate-water clusters, (SCN)(H2O)n with 3–50 water molecules, with empirical potentials describing the ion-water and water-water interactions. (It should be
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The Basin Hopping search method is used to find the global minima (GM) and map the energy landscapes of thiocyanate-water clusters, (SCN)(H2O)n with 3–50 water molecules, with empirical potentials describing the ion-water and water-water interactions. (It should be noted that beyond n = 23, the lowest energy structures were only found in 1 out of 8 searches so they are unlikely to be the true GM but are indicative low energy structures.) As for pure water clusters, the low energy isomers of thiocyanate-water clusters show a preponderance of fused water cubes and pentagonal prisms, with the weakly solvated thiocyanate ion lying on the surface, replacing two water molecules along an edge of a water polyhedron and with the sulfur atom in lower coordinated sites than nitrogen. However, by comparison with Density Functional Theory (DFT) calculations, the empirical potential is found to overestimate the strength of the thiocyanate-water interaction, especially O–H⋯S, with low energy DFT structures having lower coordinate N and (especially) S atoms than for the empirical potential. In the case of these finite ion-water clusters, the chaotropic (“disorder-making”) thiocyanate ion weakens the water cluster structure but the water molecule arrangement is not significantly changed. Full article
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