Cationic Precursor Research Articles

Engaging Two Anions with Single Cation in Energetic Salts: Approach for Optimization of Oxygen Balance in Energetic Materials.

The field of high energy density materials faces a long-standing challenge to achieve an optimum balance between energy and stability. While energetic salt formation via a combination of oxygen- and nitrogen-rich anions (providing energy) with nitrogen-containing cations (providing stability) has been a proven approach for improving physical stability, constraints such as lowering density and energetic performance remain unresolved. This can be addressed by utilizing oxygen-containing cations for salt formation. However, this approach is rarely explored because its synthesis is challenging. In this work, we have designed an oxygen-rich cationic precursor 2 by incorporating 4-amino-3,5-dinitropyrazole with 3,4-diaminotriazole via an N-methylene-C bridge. Further combination with energetic acids resulted in the formation of high-performing, physically stable energetic salts 3-10. The salts were found to be generally more energetic than the salts of respective energetic acids with previously reported cations and showed prominent improvement in physical stability with respect to their anionic precursors. All the compounds were thoroughly characterized through IR, NMR spectroscopy, HRMS, and elemental analysis. Salt 9 was confirmed through 15N NMR analysis, and salts 2 and 8 were confirmed through single-crystal X-ray diffraction. Additional analyses such as Hirshfeld surface analysis, noncovalent interaction (NCI) analysis, and electrostatic potential studies were also carried out to correlate the structure-property relationship.

Enhancing energy storage with binder-free nickel oxide cathodes in flexible hybrid asymmetric solid-state supercapacitors

The need for flexible electrode materials for the development of flexible supercapacitors has drawn scientific interest recently. We present the successful synthesis of nickel oxide thin films using the successive ionic layer adsorption and reaction (SILAR) method, with the use of three different cationic precursors. This paper provides comprehensive details on the synthesized nickel oxide structure, morphology, and elemental analysis in addition to its electrochemical characteristics, which include specific capacitance (SCs), charge transfer resistance, etc. The produced nickel oxide electrodes achieved specific capacity as 120 C g−1, 517 C g−1, and 1147 C g−1 with different nickel precursors such as nickel chloride, nickel nitrate, and nickel sulfate respectively, at a 1 mA cm−2 current density. A flexible hybrid asymmetric solid-state supercapacitor (FHASS) (S:NiO//PVA-KOH//CuS) device delivered SCs of 165 Fg−1 at a 0.5 mA cm−2 current density, with a maximum SE of 58.87 Wh kg−1 at SP 347 W kg−1. FHASS device exhibits capacitive retention and coulombic efficiency of between 79 % and 96 % after 5000 successful GCD cycles. Also, the device retained an outstanding 97 % of its capacitance at a 175º bending angle. Furthermore, to illustrate its real-world applicability, the constructed device underwent 30 s of charging to a lightning LED table lamp for 90 s. The fabricated device is bringing a new era of broad integration of device-grade applications.

Advancing Multi‐Optical Performances in Lanthanide‐Doped Fluoride Core@Shell Nanoarchitectures by Minimizing Cation Intermixing

AbstractCore/shell structures are widely employed to enhance photoluminescence efficiency and manipulate excitation dynamics in lanthanide‐doped fluoride nanoparticles (NPs). However, prominent cation intermixing leads to significant deviations from the expected optical performances, presenting a formidable challenge in a deeper understanding of the chemical processes involved, as well as developing efficient suppression methods. Here, a reliable and facile multi‐optical reference strategy to reveal the integral cation intermixing processes is designed. This strategy analyzes the presence of Ce3+ ions in the core (or shell) and their influences on near‐infrared light‐triggered upconversion (UC), ultraviolet (UV)‐activated downshifting (DS), and X‐ray‐excited optical/persistent luminescence (XEOL/XEPL) of Tb3+ ions in the shell (or core). The results demonstrate that a thin surface layer of core NPs dissolves to reach dissolution equilibrium, which then distributes throughout the entire shell layer, rather than being confined to an interfacial region. It is further developed an improved technique to greatly inhibit cation intermixing by successive shell growth with excessive cation precursors, enabling superior multi‐optical performances, including UC, DS, XEOL/XEPL, and time‐dependent multicolor evolution. The findings significantly advance the development of lanthanide‐doped fluoride core/shell NPs with superior optical performances, broadening their potential applications in bio‐medicine, healthcare, industrial inspection, and optical information science.

Facile synthesis and electrochemical properties of FeO/Fe(OH)3 nanosheets

Iron oxides and hydroxides, including Fe(OH)3 and Fe(OH)2, exhibit diverse morphologies and compositions. Nanostructures of Fe(OH)3 such as nanosheets are non-toxic and offer multiple active sites that are advantageous for catalysis. We synthesized iron oxide/iron hydroxide (FeO/Fe(OH)3) nanosheets using a surfactant-assisted method and analyzed their structure and composition. Their phase transition to iron oxyhydroxides/oxides via heat treatment were also analyzed. The formation of FeOOH, which catalyzes the oxygen evolution reaction, significantly affected the electrochemical properties. We report the morphological and crystallographic characteristics of the as-synthesized and annealed FeO/Fe(OH)3 nanosheets, highlighting the influence of specific species on their electrochemical behavior. The proposed approach is simple and efficient for the synthesis of highly crystalline transition metal oxide nanosheets using different cation precursors.

CO Oxidation at Low Temperatures over the Au Cluster Supported on Crystalline Silicotitanate.

Crystalline silicotitanate (CST) with a sitinakite structure has attracted considerable attention as an ion exchanger because of its anionic surface owing to SiO4 tetrahedral and TiO6 octahedral linked structures. In particular, the anionic surface of CST is advantageous in immobilizing single Au atoms derived from a cationic precursor such as Au(en)2Cl3 (en = ethylenediamine). In this study, a Au/CST catalyst was prepared and evaluated for CO oxidation. The transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that Au single atoms and clusters (Auδ+, 0 < δ < 1) were supported on Na+-CST particles. The 1.0 wt % Au/CST catalyst yielded high catalytic activity for CO oxidation, where 50% CO oxidation was achieved at a low temperature of -13 °C. In the low-temperature region (from -84 to 20 °C), CO oxidation over Au/CST may progress through the well-known Langmuir-Hinshelwood mechanism. Conversely, the experimental results of CO oxidation without O2 confirmed that the reaction proceeded according to the Au-assisted Mars-van Krevelen mechanism using the lattice oxygens of the CST particles at temperatures above 20 °C. Therefore, this work contributes to the design of highly dispersed single-atom or cluster catalysts using the anionic surface of the microporous CST.

(Invited) Plasmon-Driven Photochemistry for the Synthesis of Metal Nanostructures

Plasmon-driven photocatalysis with metal nanoparticles holds great promise for initiating and controlling chemical reactions at the nanoscale. One interesting application of plasmonic photochemistry involves the synthesis of metal nanostructures from cationic precursors. Despite more than twenty years of study however, this unique approach to material synthesis remains restricted to just two elements: silver (Ag) and gold (Au). To date, this process is yet to be observed with any other metals. Here, we report the plasmon-driven synthesis of copper (Cu) nanoparticles in aqueous solution via a seed-mediated growth strategy. The plasmonic synthesis is amenable to various Cu precursors, but is highly sensitive to the type of hole scavenger used in the reaction. We also found that the exclusion of oxygen from the system, both in the initial synthesis of Cu seeds and in their subsequent growth into larger nanoparticles, was essential for enabling the plasmon-driven process to proceed. A series of control experiments, supported by photoelectrochemical measurements, were performed to confirm that the growth of Cu nanoparticles occurs via plasmon excitation of the Cu seeds. Overall, our approach offers a unique route to the synthesis of Cu nanoparticles and expands the domain of plasmon-driven photochemistry to a new element.

Electrocatalytic Radical Cation Diels-Alder Reactions Using Enol Ethers As Dienophiles

Single-electron oxidation enables the conversion of electron-rich alkenes such as styrene derivatives to radical cation species. We have been developing various cycloaddition reactions of radical cations produced by single-electron oxidation using electrochemical and TiO2 photochemical methods. Introducing an electron-rich aryl group which we call a redox tag is a critical part of the process to control the reactivity of the radical cations. During carbon-carbon bonds formation the motif functions as both electron donor and electron acceptor. In addition to styrene derivatives, enol ethers can also be readily oxidized by single electron transfer (SET) electrochemically or photochemically to generate the radical cations. For instance, enol ethers tethered redox tag serves efficient radical cation precursors for [2+2] cycloadditions.[1] The cycloadditions are net redox-neutral reactions and are initiated by the formation of a radical cation by single-electron oxidation and completed by reduction after ring formation.Herein, we present [4+2] cycloadditions using enol ethers as dienophiles by electrochemical oxidation in lithium perchlorate (LiClO4)/nitromethane (MeNO2) system. In the case of disubstituted enol ethers prepared from aldehydes, the approach involving redox tag was successful in obtaining the corresponding cycloadducts, while the desired products were not obtained when the substrates without redox tag were subjected.[2] This result suggests that intramolecular electron transfer from the redox tag is crucial for the formation of the cyclohexene ring systems. In contrast, the trisubstituted enol ethers prepared from ketones allowed the cycloaddition reaction to proceed without the involvement of redox tag. It is expected that the methyl group significantly stabilizes the cyclohexene radical cations to have enough lifetime to be reduced by intermolecular SET. Furthermore, since the cycloaddition reaction of enol ether was completed with a catalytic amount of electricity (0.4 F/mol), a radical cation chain mechanism is proposed in which electron acts as a catalyst.

Structural, optical and magnetic properties of chemically grown copper oxide nanoparticles: An insight into anticancer activities

Self-assembling nanorods like copper oxide (CuO) nanoparticles (NPs) have been successfully synthesized using two different copper cationic precursors to investigate their structural, optical, and magnetic properties. These NPs are employed in anticancer applications. Both the CuO-NPs have been tested for their toxicity on human cells. The XRD patterns confirm the formation of monoclinic crystal structures for both the systems. The FESEM microstructural surface morphology shows high agglomeration and a typical elemental composition is evaluated from EDAX analysis. The HRTEM analysis reveals high crystalline CuO nanorods with diameters in the range of 60 ∼ 94 nm and 09∼ 22 nm for two different nanoparticles named CuO-NPs1 and CuO-NPs2, respectively. The optical band gap of CuO-NPs has been calculated from UV–visible absorption spectra and is found to be 2.18 eV and 2.55 eV for CuO-NPs1 and CuO-NPs2, respectively. FTIR analysis provides insights into the chemical compositions of both the CuO-NPs. Magnetization study using vibrating sample magnetometer (VSM) indicates antiferromagnetic-like properties associated with weak ferromagnetic behaviour. Cytotoxicity tests on MCF-7 cell lines show that CuO-NPs2 exhibit more pronounced effect with IC50 of 22.95 μg/mL. The toxicity of both the CuO-NPs are also assessed using human lymphocytes, suggesting that CuO-NPs could be promoted as anticancer agents while remaining non-toxic to biological systems.

Tailoring the physicochemical properties of chemically deposited MoS2 thin films for photocatalytic dye and TC degradation: effect of different cationic precursors

Tailoring the physicochemical properties of chemically deposited MoS2 thin films for photocatalytic dye and TC degradation: effect of different cationic precursors

Effect of Precursors Concentration on The Optical and Photoelectrochemical Properties of Bi₂S₃/TiO₂ Nanotubes Arrays Photoanode Synthesized by the SILAR Technique

The use of robust solar energy-driven photocatalysis materials to address the global energy and environmental crisis has gained significant attention in recent years. However, the wide band gaps in many robust semiconductor photocatalysts hinder their absorption of visible light from the solar spectrum. To address this issue, the modification of the large band gap semiconductor with the lower band gap material using the Successive Ionic Layers Adsorption and Reaction (SILAR) technique has emerged as an economical, accessible, and reproducible method for depositing nanoscale materials onto semiconductor substrates. This research aims to know how the concentration variation of cation and anion precursors in the SILAR technique affects the optical and photoelectrochemical properties of the resulting composite materials. Bi₂S₃ serves as a modifier for TiO₂ nanotube arrays (NTAs). The result shows that the cation-anion concentration ratio of 1:1.5 mM with five SILAR cycles gives the best photoelectrochemical performance, with a stable current density of 0.12 mA/cm², compared to pristine TiO₂ NTAs the current density of Bi₂S₃/TiO₂ NTAs is 15-fold. In addition, at each variation, the concentration ratio of cation and anion precursors decreases bandgap energy with each increase in the SILAR cycle.

Electrochemical Lensing for High Resolution Nanostructure Synthesis in Liquids.

The advancement of liquid phase electron/ion beam induced deposition has enabled an effective direct-write approach for functional nanostructure synthesis with the possibility of three-dimensional control of morphology. For formation of a metallic solid phase, the process employs ambient temperature, beam-guided, electrochemical reduction of precursor cations, resulting in rapid formation of structures, but with challenges for retention of resolution achievable via slower electron beam approaches. The possibility of spatial control of redox pathways via the use of water-ammonia solvents has opened avenues for improved nanostructure resolution without sacrificing the growth rate. In particular, ammonia enables "electrochemical lensing" in which a tightly confined and highly reducing environment is created locally to enable high resolution, rapid beam-directed nanostructure growth. We demonstrate this unique approach to high resolution synthesis through a combination of analysis and experiment.

The Mechanism of Rh(I)-Catalyzed Coupling of Benzotriazoles and Allenes Revisited: Substrate Inhibition, Proton Shuttling, and the Role of Cationic vs Neutral Species.

Direct coupling of benzotriazole to unsaturated substrates such as allenes represents an atom-efficient method for the construction of biologically and pharmaceutically interesting functional structures. In this work, the mechanism of the N2-selective Rh complex-catalyzed coupling of benzotriazoles to allenes was investigated in depth using a combination of experimental and theoretical techniques. Substrate coordination, inhibition, and catalyst deactivation was probed in reactions of the neutral and cationic catalyst precursors [Rh(μ-Cl)(DPEPhos)]2 and [Rh(DPEPhos)(MeOH)2]+ with benzotriazole and allene, giving coordination, or coupling of the substrates. Formation of a rhodacycle, formed by unprecedented 1,2-coupling of allenes, is responsible for catalyst deactivation. Experimental and computational data suggest that cationic species, formed either by abstraction of the chloride ligand or used directly, are relevant for catalysis. Isomerization of benzotriazole and cleavage of its N-H bond are suggested to occur by counteranion-assisted proton shuttling. This contrasts with a previously proposed scenario in which oxidative N-H addition at Rh is one of the key steps. Based on the mechanistic analysis, the catalytic coupling reaction could be optimized, leading to lower reaction temperature and shorter reaction times compared to the literature.

Manganese‐Mediated Synthesis of NHC‐Phosphine Ligand Precursors

AbstractAlkylation of N‐substituted imidazoles ImR’ (R’=2,4,6‐trimethylphenyl, 2,6‐diisopropylphenyl, 1‐adamantyl) with Mn(I) methylenephosphonium complexes [Cp(CO)2Mn(η2‐P,C‐R2P=C(H)Ph)](BF4) (PR2=PPh2, PCy2, trans‐PC(H)PhCH2CH2C (H)Ph) followed by photochemical demetallation afforded a series of bidentate NHC‐phosphine ligand precursors [R2PC(H)PhImR’](BF4) in moderate to good yield. The same strategy was successfully applied to N‐functionalized imidazoles ImL (L=2‐pyridyl, CH2SMe, CH2ImMe) to afford selectively NHC core pincer pre‐ligands featuring phosphine/thioether, phosphine/NHC and phosphine/pyridine side arms. For PCy2 derivatives, free NHCs in both bidentate and pincer series generated by deprotonation of the corresponding cationic precursors were shown to be persistent at room temperature.

Methylation of Phenyl Rings in Ester-Stabilized Phosphorus Ylides Vastly Enhances Their Protonophoric Activity.

We have recently discovered that ester-stabilized phosphorus ylides, resulting from deprotonation of a phosphonium salt such as [Ph3PCH2COOR], can transfer protons across artificial and biological membranes. To create more effective cationic protonophores, we synthesized similar phosphonium salts with one ((heptyloxycarbonylmethyl)(p-tolyl)bromide) or two ((butyloxycarbonylmethyl)(3,5-xylyl)osphonium bromide) methyl substituents in the phenyl groups. The methylation enormously augmented both protonophoric activity of the ylides on planar bilayer lipid membrane (BLM) and uncoupling of mammalian mitochondria, which correlated with strongly accelerated flip-flop of their cationic precursors across the BLM.

Stabilizing Monoatomic Two-Coordinate Bismuth(I) and Bismuth(II) Using a Redox Noninnocent Bis(germylene) Ligand.

The formation of isolable monatomic BiI complexes and BiII radical species is challenging due to the pronounced reducing nature of metallic bismuth. Here, we report a convenient strategy to tame BiI and BiII atoms by taking advantage of the redox noninnocent character of a new chelating bis(germylene) ligand. The remarkably stable novel BiI cation complex 4, supported by the new bis(iminophosphonamido-germylene)xanthene ligand [(P)GeII(Xant)GeII(P)] 1, [(P)GeII(Xant)GeII(P) = Ph2P(NtBu)2GeII(Xant)GeII(NtBu)2PPh2, Xant = 9,9-dimethyl-xanthene-4,5-diyl], was synthesized by a two-electron reduction of the cationic BiIIII2 precursor complex 3 with cobaltocene (Cp2Co) in a molar ratio of 1:2. Notably, owing to the redox noninnocent character of the germylene moieties, the positive charge of BiI cation 4 migrates to one of the Ge atoms in the bis(germylene) ligand, giving rise to a germylium(germylene) BiI complex as suggested by DFT calculations and X-ray photoelectron spectroscopy (XPS). Likewise, migration of the positive charge of the BiIIII2 cation of 3 results in a bis(germylium)BiIIII2 complex. The delocalization of the positive charge in the ligand engenders a much higher stability of the BiI cation 4 in comparison to an isoelectronic two-coordinate Pb0 analogue (plumbylone; decomposition below -30 °C). Interestingly, 4[BArF] undergoes a reversible single-electron transfer (SET) reaction (oxidation) to afford the isolable BiII radical complex 5 in 5[BArF]2. According to electron paramagnetic resonance (EPR) spectroscopy, the unpaired electron predominantly resides at the BiII atom. Extending the redox reactivity of 4[OTf] employing AgOTf and MeOTf affords BiIII(OTf)2 complex 7 and BiIIIMe complex 8, respectively, demonstrating the high nucleophilic character of BiI cation 4.

Effect in variation of the cationic precursor temperature on the electrical and crystalline properties of MnS growth by SILAR

The crystallographic, optical, and electrical properties of manganese sulfide thin films depend on the control of the temperature precursors in the synthesis process, as shown by the results of this work. MnS thin films were deposited on glass substrates using the SILAR method and over an additional layer of CdS synthesized by chemical bath deposition (CBD) to acquire a p-n heterojunction. SILAR is an inexpensive method performed with a homemade robot in this case. Temperature in the solution precursors varied from 20 to 80 °C in four experiments. The morphology and structure of MnS and FTO/CdS/MnS thin films were studied through scanning electron microscopy (SEM) and grazing-incidence X-ray diffraction (GIXRD); the results indicate that materials showed a polycrystalline behavior, a diffraction peak of α- MnS cubic phase was observed with lattice constants values, ranging from 4.74 to 4.75 Å.Additionally, Raman spectroscopy showed a signal corresponding to the transversal optical phonons of MnS at a wavenumber near 300 cm−1. UV–vis spectroscopy showed optical bandgap values of 3.94, 4.0, 4.09, and 4.26 eV for thin films obtained at 20°, 40°, 60°, and 80 °C.respectively. Results indicated 80 °C as an optimal cationic precursor process temperature, achieving optical transmittance T% and good film quality according to SEM and GIXRD for the synthetization of MnS. The current–voltage (I–V) characterization in the heterojunction showed a characteristic diode curve with an open circuit voltage (VOC) of 300 mV under illumination, which indicated that the manganese sulfide behaves as p-type material contributing with positive charge carriers, while CdS behaves as n-type material.

Taming nonclassical carbocations to control small ring reactivity.

Prediction of the outcome of ring opening of small organic rings under cationic conditions can be challenging due to the intermediacy of nonclassical carbocations. For example, the solvolysis of cyclobutyl or cyclopropylmethyl derivatives generates up to four products on nucleophilic capture or elimination via cyclopropylcarbinyl and bicyclobutonium ions. Here, we show that such reaction outcomes can be controlled by subtle changes to the structure of nonclassical carbocation. Using bicyclo[1.1.0]butanes as cation precursors, the regio- and stereochemistry of ring opening is shown to depend on the degree and nature of the substituents on the cationic intermediates. Reaction outcomes are rationalized using computational models, resulting in a flowchart to predict product formation from a given cation precursor.

"Catch and release" of the CpN3 ligand using cobalt: dissociation, protonation, and C-H bond thermochemistry.

The coordination chemistry of an amine-rich CpN3 ligand has been explored with cobalt. We demonstrate that in the presence of NaCo(CO)4, the cationic precursor [CpN3]+ yields the complex CpN3CoI(CO)2. While 2e- oxidation generates new CoIII complexes such as [CpN3Co(NCMe)3]2+ and CpN3CoI2(CO), subsequent ligand loss is facile, generating free [CpN3]+ or the protonated dication [CpN3H]2+. We have structurally characterized both these ligand release products via single crystal X-ray diffraction and obtained thermochemical C-H bond strengths via experiment and density functional theory (DFT). Upon reversible 1e- reduction, the radical cation [CpN3H]˙+ has a weak C-H BDFE of 52 kcal mol-1 in acetonitrile. Mechanistic analysis shows that [CpN3H]˙+ undergoes radical-radical disproportionation in the absence of exogenous H-atom acceptors, which is supported by deuterium isotope labelling experiments. Structural comparison of these organic molecules shows a high degree of iminium-like electron delocalization over the C-N bonds connected to the central five-membered ring.

SILAR Deposition of Sns Thin Films for Possible Device Applications

Successive Ionic Layer Adsorption and Reaction (SILAR) was used to deposit tin sulphide (SnS) thin films on glass substrates at temperature of 450C.Sodium thiosulphateNa2S2O3solution was used as the anionic precursor, tin chloride SnCl2 solution as the cationic precursor and EDTA as complexing agent. The samples were subjected to annealing at the temperature range of 2000C and 250oC). High transmittance values were obtained in both Samples C and D in the UV(70% -72%) and (75% - 89%) respectively atthe wavelength range of (350nm-400nm) which maintains linear characteristics through the visible to near infrared regions (NIR) of the electromagnetic spectrum. This high transmittance implies that it can be useful in the areas of solar energy and opto-electronic applications. The Energy band gap (Eg) is obtained using the relation (αhv)2= A (hv-Eg) where A is constant, hv is the photon energy, Eg is the energy band gap and α is the absorption coefficient. Direct band gap value of 2.90±0.05eV is obtained for sample C while a direct band gap of 2.70±0.05eV is obtained for sample D. The two samples have average band gap of 2.8±0.05eV.

Boron diamide derivatives containing N-N and N-P molecular fragments.

The cationic and neutral boron-diamide precursors are employed to target the inclusion of N2 and N-P molecular fragments. The species (HCN(Dipp))2BNH25, and (H2CN(Dipp))2BNH26 were prepared. While efforts to oxidize with [NO]+ gave mixtures of products, reactions with N2H4 gave the salts [(HCN(Dipp))2B(NHNH3)][O3SCF3] 7 [(H2CN(Dipp))2B(NHNH3)][O3SCF3] 8. Excess N2H4 gave the neutral species (HCN(Dipp))2B(NHNH2) 9 and (H2CN(Dipp))2B(NHNH2) 10, respectively. The species (H2CN(Dipp))2B(N3) 11 was prepared for comparative purposes. Turning to related NP species, compound 6 was converted to (HCN(Dipp))2B(NHPCl2) 12, while (HCN(Dipp))2BNK(SiMe3) 14 was used to give (HCN(Dipp))2BN(SiMe3)PCl215. Replacement of one of the chlorides gave (HCN(Dipp))2BN(SiMe3)PCl(OSO2CF3) 16 which converts to [(HCN(Dipp))2BNPCl]217. Similarly heating 15 afforded 17. The insights for the synthesis of further boron-N2 and boron-NP derivatives are discussed.