Solvent Coordination Research Articles

Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes.

The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N'-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N'-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.

Two Polynuclear Fe Complexes with Boat-like Core: Syntheses, Structures and Magnetic Properties

Two novel polynuclear complexes {NaFe4(µ4-O)(L)4(µ2-Cl)[Fe(CN)5NO](H2O)(DMF)2} (1) and {NaFe4(µ4-O)(L)4(µ2-OEt)[Fe(CN)5NO](H2O)(DMF)2} (2) have been prepared using the tetradentate N-(2-hydroxyethyl)-3-methoxysalicylaldimine Schiff-base ligand (H2L) with the help of [Fe(CN)5NO]2- linkers, where the ligand was in situ synthesized through the condensation of o-vanillin and ethanolamine in the formation process of complexes. The resulting complexes possess “boat-like” structure constructed through three Fe ions and one Na ion with the fourth Fe ion acting as the “paddle”. The “hull bottom” contains an eight-membered metallamacrocycle with metallacrown-like motif and [-M-O-] repeat unit. Both complexes display three-dimensional frameworks through C-H···N hydrogen bonds, C–H···Cl hydrogen bonds, and π-π stacking interactions with the introduction of solvent molecules and coordination anions. Variable-temperature magnetic susceptibility measurements reveal strong antiferromagnetic couplings between the metal centers in complexes 1 and 2.

Dissipatons as generalized Brownian particles for open quantum systems: Dissipaton-embedded quantum master equation.

Dissipaton theory had been proposed as an exact, nonperturbative approach to deal with open quantum system dynamics, where the influence of the Gaussian environment is characterized by statistical quasi-particles, named dissipatons. In this work, we revisit the dissipaton equation of motion theory and establish an equivalent dissipaton-embedded quantum master equation (DQME) that gives rise to dissipatons as generalized Brownian particles. As explained in this work, the DQME supplies a direct approach to investigate the statistical characteristics of dissipatons and, thus, the physically supporting hybrid bath modes. Numerical demonstrations are carried out on the electron transfer model, exhibiting the transient statistical properties of the solvation coordinate.

Unraveling Deposition Atmosphere Impact on Reproducibility of Perovskite Light-Emitting Diodes.

Manipulating the crystallization dynamics of perovskite emitters is an effective strategy for preparing high-performance perovskite light-emitting diodes (PeLEDs). In general, amorphous-like thermodynamically stable intermediates are desirable for a retarded and controllable crystallization process of perovskite emitters. Despite a variety of well-demonstrated strategies for crystallization control, it has been generally realized that perovskite thin-film emitters show problematic reproducibility. Here, we unraveled that the coordinating solvent vapor residues could raise deleterious influences on the formation of amorphous intermediate phases, which thus leads to varying crystal qualities from batch to batch. We demonstrated that undesirable crystalline intermediate phases tend to form with a strong coordination solvent vapor atmosphere, which alters the crystallization process and thus brings about additional ionic defects. By applying an inert gas flush strategy, this detrimental effect could be effectively mitigated, enabling PeLEDs with high reproducibility. This work provides new insight into the fabrication of efficient and reproducible perovskite optoelectronics.

Influence of solvent coordination on crystal structure and luminescent property in lanthanide MOFs

Two isomorphous Ln-MOFs with pyridine-2, 4, 6-tricarboxylic acid (H3PTC), Eu-PTC-DMF and Tb-PTC-DMF, were prepared by solvothermal synthesis method and characterized by IR spectroscopy, and thermogravimetric analysis, and powder X-ray diffraction techniques. Single-crystal structural analyses indicate that the Ln1 and Ln2 coordination polyhedra are connected by sharing corners of polyhedra to construct 1D chain, which further form a 3D coordination framework through the connection of PTC3- ligands, and the solvent molecules of DMF and H2O, as the terminal ligands, are bound to polyhedra of Ln3+ ions. Investigation of the photophysical property at ambient conditions revealed that both Ln-MOFs emit characteristic luminescence of Ln3+ ions. Eu-PTC-DMF and Tb-PTC-DMF possess microsecond scale emission lifetime with absolute quantum yields as high as 33.1% and 50.8%, respectively.

Revealing the Multifunctions of Li3N in the Suspension Electrolyte for Lithium Metal Batteries

Inorganic-rich solid-electrolyte interphases (SEIs) on Li metal anodes improve the electrochemical performance of Li metal batteries (LMBs). Therefore, a fundamental understanding of the roles played by essential inorganic compounds in SEIs is critical to realizing and developing high-performance LMBs. Among the prevalent SEI inorganic compounds observed for Li metal anodes, Li3N is often found in the SEIs of high-performance LMBs. Herein, we elucidate new features of Li3N by utilizing a suspension electrolyte design that contributes to the improved electrochemical performance of the Li metal anode. Through empirical and computational studies, we show that Li3N guides Li electrodeposition along its surface, creates a weakly solvating environment by decreasing Li+-solvent coordination, induces organic-poor SEI on the Li metal anode, and facilitates Li+ transport in the electrolyte. Importantly, recognizing specific roles of SEI inorganics for Li metal anodes can serve as one of the rational guidelines to design and optimize SEIs through electrolyte engineering for LMBs.

Copper(II) complexes containing derivative of aminobenzoic acid and nitrogen-rich ligands: Synthesis, characterization and cytotoxic potential

Four mixed ligand copper(II) complexes bearing mefenamic acid and different heterocyclic nitrogen donor ligands have been synthesized. A direct one-step metal-ligand complexation method was adopted in synthesizing the complexes. These newly formed complexes are [Cu(mef)2(imi)2]; CM-1, [Cu(mef)2(py)2]; CM-2, [Cu2(mef)4(apy)2].2CH3CN; CM-3, and [Cu(mef)2(nic)2(C2H5OH)]; CM-4 (mef = mefenamato, imi = imidazole, py = pyridine, apy = 2-aminopyridine, and nic = nicotinamide). The complexes were characterized by both analytical and spectral methods. FTIR studies confirmed the mefenamato ligand coordinated via a deprotonated carboxylato oxygen atom to the Cu(II) center. The molecular structures of CM-1 and CM-2 showed both are isostructural and exhibit square-planar geometry around Cu(II). CM-3 crystallized in the dimeric form, each Cu(II) is in five-coordinate geometry, with a structural paddle wheel motif. The resulting square pyramidal geometry in CM-4 is due to the ethanol solvent's coordination on the pyramid's axial position. The crystal lattice of the complexes was stabilized by noncovalent interactions such as N-H···O, C-H···O, CH···π, and π···π. The mononuclear complexes were more stable than the dimeric complex CM-3, revealed by thermogravimetric analysis. In addition, the cytotoxic study of the copper (II) complexes on lung carcinoma cells (NCIH-460) and breast cells (MDAMB) were evaluated using MTT dye (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.

Effect of a Weak Coordination Solvent on a Kinetically Favorable Electrode Reaction in Concentrated Lithium-Ion Battery Electrolytes

We present highly concentrated electrolytes prepared with a fluorinated acetate solvent that has much weaker coordination power, allowing for a kinetically favorable electrode reaction in lithium (Li)-ion batteries (LIBs). Among the concentrated electrolytes using conventional organic solvents, the concentrated electrolyte containing a 2,2,2-trifluoroethyl acetate (TFEAc) solvent and 3.2 mol dm–3 LiFSA salt (FSA: bis(fluorosulfonyl)amide) had the lowest ionic conductivity but a wide electrochemical window (∼5 V), allowing for a LIB electrode reaction. Compared to an analogous electrolyte containing LiTFSA salt (TFSA: bis(trifluoromethanesulfonyl)amide), the concentrated LiFSA/TFEAc electrolyte demonstrated significantly improved charge–discharge behavior with a high C-rate performance on the graphite negative electrode. The activation energy (Ea) of the graphite electrode reaction (i.e., Li+-insertion reaction) was determined experimentally to be Ea = 19.9 kJ mol–1 in the concentrated LiFSA/TFEAc electrolyte, which was significantly lower than that reported previously for dilute carbonate-based electrolytes. Furthermore, a combination of high-energy X-ray total scattering experiments and all-atom molecular dynamics simulations revealed that Li ions are co-coordinated with TFEAc molecules and FSA anions to form intricate ion-ordered complexes in the bulk solution with no free solvent and counteranion. From a structural viewpoint, we discussed the characteristic Ea in the current concentrated electrolyte system and concluded that the weak interaction between Li-ion and TFEAc remaining in the activation state plays a key role in triggering energetically easier decoordination during the charge transfer process, achieving a kinetically unique graphite electrode reaction.

Multiple promotion effect of mixed solvents on the oxidative degradation of thermosetting polymers

Mixed solvents significantly promote oxidative degradation of thermosets without heat input by improving mass transfer via promoting resin swelling while improving oxidation activity of oxidizer through coordination of organic solvent with metal.

Zinc vacancy mediated electron-hole separation in ZnO nanorod arrays for high-sensitivity organic photoelectrochemical transistor aptasensor.

A novel strong solvent coordination leaching method was developed to prepare surface zinc vacancies in ZnO nanorod arrays. Remarkably, the surface-zinc-vacancy-rich ZnO nanorod arrays exhibit high electron-hole separation efficiency and excellent photoelectrochemical performance for use as a promising candidate for the next generation of organic photoelectrochemical transistor aptasensors.

Behavior of the aqueous sodium chloride solutions from molecular simulations and theories

Molecular simulations and theories are important tools for studying electrolyte solutions. In this work, molecular dynamics simulations with one of the most widely used force field combination of water and alkali and halide monovalent ion parameters were first conducted for the aqueous sodium chloride solutions to predict density, self-diffusion coefficients and molar conductivity. Then the radial distribution functions were analyzed to obtain the first shell solvation radii and coordination numbers of ions, which were found practically unchanged against concentration. Together with the force field parameters, they were further applied into various molecular theories to predict the Gibbs energy of solvation, static relative permittivity, mean ionic activity coefficients and molar conductivity. It is remarkable to see that the mean ionic activity coefficients and molar conductivity can be predicted with deviations of 1.1 % and 1.4 %, respectively, up to 6 mol/kg H2O.

Solvent Coordination Effect on Copper-Based Molecular Catalysts for Controlled Radical Polymerization

The equilibrium of copper-catalyzed atom transfer radical polymerization was investigated in silico with the aim of finding an explanation for the experimentally observed solvent effect. Various combinations of alkyl halide initiators and copper complexes in acetonitrile (MeCN) and dimethyl sulfoxide (DMSO) were taken into consideration. A continuum model for solvation, which does not account for the explicit interactions between the solvent and metal complex, is not adequate and does not allow the reproduction of the experimental trend. However, when the solvent molecules are included in the coordination sphere of the copper(I,II) species and the continuum description of the medium is still used, a solvent dependence of process thermodynamics emerges, in fair agreement with experimental trends.

Vacuum-Induced Guest N,N'-Diethylformamide Binding in a Metastable Cd5-Based Metal-Organic Framework.

A three-dimensional (3D) metal-organic framework (MOF) of [Et2NH2]2[Cd5(BTB)4(DEF)2]·4.75DEF (1; H3BTB = benzene-1,3,5-tribenzoic acid and DEF = N,N'-diethylformamide) sustained by symmetrical Z-shaped Cd5 secondary building units (SBUs) with an intrinsically metastable host framework has been prepared and characterized. Upon gentle vacuum (800 Pa) at 50 °C, some encapsulated DEF solvates are released, leading to pore-shape changes and Cd2+ coordination geometry distortion. This is followed by DEF solvate migration to only one end of the SBU with concomitant symmetry breaking. Additional time under vacuum promoted further structural distortion and topology changes as authenticated by single-crystal X-ray diffraction studies. This work was initially inspired by unusual gas adsorption isotherms and points to the potentially complicated, nonspectator role of coordinative solvents such as DEF during MOF activation.

Regulating solvation structure in gel polymer electrolytes with covalent organic frameworks for lithium metal batteries

Stable and safe Li metal anodes are urgent demands for high-energy-density lithium metal batteries (LMBs). The safety concern of LMBs roots in the intrinsic high reactivity of the solvent sheath with Li metal, and the solvent-oriented fragile solid electrolyte interphase (SEI) causes the continuation of malignant reaction and Li dendrite growth. The SEI composition is closely related to the solvation structure of electrolytes. Furthermore, it is also necessary to alleviate the leakage of liquid electrolytes. Herein, regulating solvation structure by the covalent organic framework (COF) in gel polymer electrolyte (GPE) prepared with a one-step radiation method is proposed to achieve superior cycle performance and leakage-free safety in batteries. The COF with a unique channel structure and abundant lithophilic groups of amino and aldehyde (TpPa-2) exists in strong interfacial interaction with solvated Li + and thus interferes with Li + -solvent coordination. The TpPa-2 modified GPE with increased intimate ion pairs results in the construction of an anion-derived, LiF-rich SEI to regulate Li plating/stripping. The resultant LiFePO 4 (LFP)//Li coin cell demonstrates superior capacity retention (75%, 1000 cycles) at 0.5 C. Furthermore, the assembled LFP//Li pouch cell displays excellent flexibility and the capability of resisting LE leakage. This study demonstrates an effective strategy of offering dependable COF-modified GPE to develop LMBs and provides a new horizon into the character of the COF in the long-term cycle performance of LMBs.

Effects of Counterions, Coordination Anions, and Coordination Solvent Molecules on Single-Molecule Magnetic Behaviors and Nonlinear Optical Properties of Chiral Zn2Dy Schiff Base Complexes.

By changing the counterions (ClO4- and CF3SO3-) and the coordination anions (Cl- and Br-), we investigated their influences on the structures and performances of a class of Zn2Dy chiral single-molecule magnets (SMMs), which are based on a pair of chiral Schiff bases R,R-H2LSchiff and S,S-H2LSchiff {R,R-H2LSchiff = 2-((E)-((1R,2R)-2-((E)-2-hydroxy-3-methoxybenzylideneamino)cyclohexylimino)methyl)-6-methoxyphenol and S,S-H2LSchiff = 2-((E)-((1S,2S)-2-((E)-2-hydroxy-3-methoxybenzylideneamino)cyclohexylimino)methyl)-6-methoxyphenol}. Three pairs of chiral Zn2Dy Schiff base complexes were obtained by directed synthesis, which are [DyZn2(R,R-LSchiff)Cl2(H2O)](ClO4)·0.5MeOH·0.25H2O (R-1) and [DyZn2(S,S-LSchiff)Cl2(H2O)][DyZn2(S,S-LSchiff)Cl2(MeOH)](ClO4)2·MeOH·0.5H2O (S-1), [DyZn2(R,R-LSchiff)Cl2(H2O)](CF3SO3)·0.5MeOH (R-2) and [DyZn2(S,S-LSchiff)Cl2(H2O)][DyZn2(S,S-LSchiff)Cl2(MeOH)](CF3SO3)2·MeOH (S-2), and [DyZn2(R,R-LSchiff)Br2(H2O)](CF3SO3)·0.25MeOH (R-3) and [DyZn2(S,S-LSchiff)Br2(H2O)][DyZn2(S,S-LSchiff)Br2(MeOH)](CF3SO3)2 (S-3). They all exhibit good SMM behaviors, and their magnet relaxation is regulated by not only the counterions (ClO4- and CF3SO3-) but also the coordination anions (Cl- and Br-); these anions also have important effects on the second-harmonic generation (SHG) and third harmonic generation (THG) nonlinear optical properties. Interestingly, in the S-configuration complexes, the coordination solvent molecule of the Dy3+ ion on half of the molecules is the methanol molecule instead of the water molecule. This change in the coordinating solvent molecule can also significantly affect the SMM behaviors and the SHG and THG nonlinear optical properties. Moreover, ab initio calculations were applied to rationally explain the SMM properties.

Impact of Electrolyte Chemistry and Solvation on Interphasial Ion Dynamics for Low-Temperature Li Metal Batteries

The influence of electrolyte chemistry on the ion-desolvation process of charge-transfer in Li-based batteries is a crucial, yet murky aspect of their design and operation. This desolvation process has been shown to be a dominant factor for the low-temperature operation of batteries, where high energy density is necessary, but difficult to achieve. We have applied Li metal batteries in an attempt to provide such metrics, which show extremely disparate performance depending on the electrolyte applied in each cell. Specifically, we have found that the induction of ion-pairing and the inclusion of weakly-bound solvents results in a substantial improvement in both the reversibility and shorting behavior when plating Li at low-temperature, despite significant loss in the bulk ionic conductivity of the solution. To provide a deeper understanding of these experimental observations, we also apply free-energy sampling techniques at 298 and 213 K to simulations involving diethyl ether (DEE) and 1,3-dioxoloane/1,2-dimethoxyethane (DOL/DME) electrolytes, which display bulk solvation structures dominated by ion-pairing and solvent coordination, respectively. We find that the degree of ion-pairing in the electrolyte bulk and at the interphase plays a vital role in assisting the delivery of Li+ to the inner Helmholtz layer, and that the sterics of DME are prone to Li+ over-coordination in solution. This mechanistic reliance of ion-pairing at the interphase conflicts with the preferred solvent-dominated structure of the DOL/DME system, which is further emphasized at 213 K, where simulations predict that the balance between solvent and anion coordination is shifted significantly in favor of solvent. This work endeavors to provide unambiguous evidence of the importance of the solvation structure for interphasial charge-transfer kinetics as well as a mechanistic understanding of the phenomena at the interphase. Figure 1

Redox Couple Stability Studies for Thermodynamic Reference Electrodes and Fluoroacidity Investigation

A stable reference electrode is essential for electrochemical studies in molten fluoride salts, yet reference electrode design is hindered by challenges such as materials compatibility and high temperature operation. Electroanalytical studies are relevant to sensor development for molten fluoride salt systems as well as fundamental chemistry studies of salt structure and speciation. Dynamic reference electrode techniques have been used to find benchmark reference potentials, but the application of a constant current for the technique may not be feasible for sensing or high throughput studies. A thermodynamic reference electrode which is durable, stable, and reproduceable is urgently needed for both scientific studies and engineering applications of molten fluoride salts.Fluoroacidity studies are of particular interest for a fundamental understanding of molten salt speciation. The more dissociated fluoride anions present in a melt, the more of a fluorodonor it is. Thus, it is considered to have a higher fluorobasicity due to its Lewis base behavior. Fluoroacidity is related to the coordination of solvent and solute ions and, therefore, solute diffusion coefficients and viscosity. Ion solvation differs in fluoride salts of various fluoroacidities, so solvated ions have different activity coefficients in different fluoride solvents. The relationship between activity coefficients of solvated ions and a melt’s fluoroacidity is not fully understood. The electrochemical determination of these activity coefficients benefits from a stable reference electrode. In addition, quantification of fluoroacidity requires the measurement of the activity of dissociated fluoride, which can be done electrochemically. The measurement of redox potential of a given couple in various fluoride melts can lead to a classification of the solvent melts based on the Nernst equation. Therefore, the study of redox couple behavior in various fluoride melts is relevant to both the development of a robust thermodynamic reference electrode & the quantification and theory of fluoroacidity.The Ni/NiF2 and Ag/AgF redox couples have been previously investigated for use in thermodynamic reference electrodes for molten fluoride salt. Ni/NiF2 has been characterized for its stability in molten fluorides. The Ag/AgCl redox couple has commonly been used for chloride mixtures but literature on the fluoride couple is marginal. Our preliminary studies have shown the stability of the Ag/AgF redox couple in a FLiNaK melt by OCP measurement. Polarization studies will be carried out to test for reversibility, and other redox couples may be investigated. In this presentation, we present results from the Ag/AgF redox couple studies in FLiNaK, as well as their impact on current understandings of fluoroacidity.

Design Guidelines for Sulfonyl/Sulfamoyl Fluoride Electrolyte Additives for Modulation of Lithium Anode Coulombic Efficiency

Owing to its high theoretical capacity (3860 mAh/g, over 10 times that of graphite) and its lowest theoretical electrochemical potential (-3.04 V vs SHE), Li metal is an ideal anode material for improving the capacity of rechargeable Li batteries [1]. However, the practical application of the Li anode is severely hindered by its high reactivity with standard electrolyte compositions, which results in limited Coulombic efficiency (CE) in those electrolytes (for instance, 85-90% with 1 M LiPF6 EC:DEC [2]). Strategies to improve CE have focused on electrolyte engineering, including development of highly concentrated electrolytes (HCE) and more recently, local high-concentration electrolytes (LHCE) [3]. A feature shared by these strategies is the promotion of contact-ion pairing, which enhances anion contributions to the solid electrolyte interphase (SEI). Among the best-performing salts are fluorinated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI), which are believed to promote stable inorganic-rich SEIs and correlate with higher CE [4]. A second strategy of interest is to pursue development of additives incorporated at relatively low concentrations (e.g., 2-5 wt%) that can favorably alter the SEI, such as carbonates (e.g., vinylene carbonate (VC) [5] and fluoroethylene carbonate (FEC) [6]), sulfates (e.g., ethylene sulfate (DTD) and 1,3-propanesulfonate (PS) [7]), and borates (e.g., lithium difluoro(oxoalate) borate (LiDFOB) [8] and tris (2,2,2-trifluoroethyl) borate (TTFEB) [9]). An advantage of this strategy is the possibility to ultimately lower reliance on high fluorinated salt concentrations, which are costly and can be corrosive towards the Al current collector, and potentially expand the versatility of available electrolyte frameworks having competitive CE. However, compared to the principles developed for salt and solvent selection in HCE and LHCE, the mechanism behind successful additive activation needs elucidation.In this work, we examined the potential of "FSI-like," neutral sulfonyl/sulfamoyl fluorides (R-SO2F and R-R’-NSO2F, Figure 1) as functional additives for Li cycling, motivated by their structural similarity to the high-performance FSI- anion. The examined baseline electrolytes include high-CE systems consisting of LiFSI dissolved in various solvents: fluoroethylene carbonate (FEC, 1 and 4 M salt), 1,2-dimethoxyethane (DME, 4 M), and dimethyl carbonate (DMC, 6 M). The ability for each additive to coordinate with Li+ was first examined by NMR, with trends rationalized in part by supporting microcalorimetry data on the degree of solvent coordination strength. We relate these to CE and cycling outcomes in each electrolyte. Interestingly, we find that additives have negligible effect on CE in FEC-based electrolytes, whereas significant impacts were observed in DME and DMC. We relate these diverse outcomes to the SEI chemical compositions and gases evolved during galvanostatic cycling, as characterized by X-ray photoelectron spectroscopy (XPS) and gas chromatography (GC), which help to rationalize competitive reactions among solvent, anion, and additive. Unfortunately, additives had a negative-to-neutral impact on CE in these systems. Thus, we finally examined a LiPF6 in carbonate electrolyte, 1 M LiPF6 in EC/DMC (LP40), where we hypothesized that competitive reduction of coordinating additives over problematic carbonate solvent would lead to performance gains. Indeed, significant improvements (up to 94%, compared to baseline 89% over the initial 50 cycles) in CE were observed for two additives, with their structural advantages further discussed. Overall, our findings provide insights into the effects of sulfonyl/sulfamoyl fluoride additive structures on Li metal cyclability and the compositions of baseline electrolytes whose electrochemical cycling stability can be effectively modulated by these additives. Xu, W., et al., Lithium metal anodes for rechargeable batteries. Energy & Environmental Science, 2014.7(2):p.513-537.Genovese, M., et al., Combinatorial methods for improving lithium metal cycling efficiency. Journal of The Electrochemical Society, 2018.165(13):p.A3000.Hobold, G.M., et al., Moving beyond 99.9% Coulombic efficiency for lithium anodes in liquid electrolytes. Nature Energy, 2021.6(10):p.951-960.Suo, L., et al., Fluorine-donating electrolytes enable highly reversible 5-V-class Li metal batteries. Proceedings of the National Academy of Sciences, 2018.115(6):p.1156-1161.Aurbach, D., et al., On the use of vinylene carbonate (VC) as an additive to electrolyte solutions for Li-ion batteries. Electrochimica acta, 2002.47(9):p.1423-1439.Markevich, E., et al., Fluoroethylene carbonate as an important component in electrolyte solutions for high-voltage lithium batteries: role of surface chemistry on the cathode. Langmuir, 2014.30(25):p.7414-7424.Han, B., et al., Poor Stability of Li2CO3 in the Solid Electrolyte Interphase of a Lithium ‐Metal Anode Revealed by Cryo ‐Electron Microscopy. Advanced Materials, 2021.33(22):p.2100404.Liu, J., et al., Lithium difluoro (oxalato) borate as a functional additive for lithium-ion batteries. Electrochemistry communications, 2007.9(3):p.475-479.Ma, Y., et al., Enabling reliable lithium metal batteries by a bifunctional anionic electrolyte additive. Energy Storage Materials, 2018.11:p.197-204. Figure 1. (a) Sulfonyl/sulfamoyl fluoride chemical structures and (b) R-S and S-F bond lengths calculated by density functional theory. Figure 1

Controllable Structural Modulation: Assembling Variable Dimension Energetic Metal-Organic Frameworks via Free Protons.

Herein, we provide an efficient strategy for constructing three-dimensional (3D) energetic coordination polymers (ECPs), namely, metal-organic frameworks (EMOFs), avoiding solvent coordination without changing the organic ligands or metal nodes. Three ECPs with the same ligand and metal center, namely, two-dimensional (2D) layer ECP [Pb(HOBTT)(H2O)2]n (1), 3D solvent-free EMOFs [Pb(HOBTT)]n (2), and dense [Pb3(OBTT)2]n (3) (H3OBTT = 4,5-bis(1-hydroxytetrazol-5-yl)-2H-1,2,3-triazole), were rationally designed and synthesized via free protons. As expected, the theoretical density of 3 (4.080 g·cm-3) is greater than those of 2 (3.299 g·cm-3) and 1 (3.055 g·cm-3). Thermal stabilities indicate that their decomposition temperature exceeds 300 °C. Theoretical calculations show that the detonation performance of 3 is better than that of 1 and 2. The detonation performance of 1-3 was further proven by laser irradiation.

Synthesis, Covalency Sequence, and Crystal Features of Pentagonal Uranyl Acylpyrazolone Complexes along with DFT Calculation and Hirshfeld Analysis.

Three uranyl acylpyrazolone complexes [UO2(PCBPMP)2(CH3CH2OH)] (complex I), [UO2(PCBMCPMP)2(CH3CH2OH)] (complex II), and [UO2(PCBPTMP)2(CH3CH2OH)] (complex III) were synthesized from σ-donating acypyrazolone ligands to analyze their sequence of covalent characteristics, reactivity, and redox properties (PCBPMP: p-chlorobenzoyl 1-phenyl 3-methyl 5-pyrazolone; PCBMCPMP: p-chlorobenzoyl 1-(m-chlorophenyl) 3-methyl 5-pyrazolone; PCBPTMP: p-chlorobenzoyl 1-(p-tolyl) 3-methyl 5-pyrazolone). An examination of the structure, pentagonal bipyramidal geometry, and composition of these complexes was conducted mainly through their single-crystal X-ray diffraction (XRD) data, 1H nuclear magnetic resonance (NMR) δ-values, plots of thermogravimetric-differential thermal analysis (TG-DTA), significant Fourier transform infrared (FTIR) vibrations, gravimetric estimation, and molar conductivity values. The covalency order was found to be complex II > III > I, which mainly depends on values of stretching frequencies, average bond lengths of axial uranyl bonds, values of average bond lengths on the pentagonal equatorial plane, solvent coordination on the fifth site of a pentagonal plane, and the type of aryl group on the nitrogen of the pyrazolone ring. This was confirmed by FTIR spectroscopy and single-crystal spectral characterization. To verify experimental results by comparison with theoretical results, density functional theory (DFT) calculations were carried out, which further gives evidence for the covalency order through theoretical frequencies and the gap of highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies. Theoretical bond properties were also examined by the identification of global index parameters. Intermolecular noncovalent surface interactions were studied by the Hirshfeld surface analysis. The irreversible redox behavior of uranyl species was identified through electrochemical cyclic voltammetry-differential pulse voltammetry (CV-DPV) plot analysis.