Complex Solvent Research Articles

Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator.

The uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO3 nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO3 nanoparticles and the polar solvent reduces the ionic radius of the Li+ -solvent complex, thus increasing the Li+ transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO3 nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi2 at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.

Solution Structures of Europium Terpyridyl Complexes with Nitrate and Triflate Counterions in Acetonitrile.

Lanthanide-ligand complexes are key components of technological applications, and their properties depend on their structures in the solution phase, which are challenging to resolve experimentally or computationally. The coordination structure of the Eu3+ ion in different coordination environments in acetonitrile is examined using ab initio molecular dynamics (AIMD) simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy. AIMD simulations are conducted for the solvated Eu3+ ion in acetonitrile, both with or without a terpyridyl ligand, and in the presence of either triflate or nitrate counterions. EXAFS spectra are calculated directly from AIMD simulations and then compared to experimentally measured EXAFS spectra. In acetonitrile solution, both nitrate and triflate anions are shown to coordinate directly to the Eu3+ ion forming either ten- or eight-coordinate solvent complexes where the counterions are binding as bidentate or monodentate structures, respectively. Coordination of a terpyridyl ligand to the Eu3+ ion limits the available binding sites for the solvent and anions. In certain cases, the terpyridyl ligand excludes any solvent binding and limits the number of coordinated anions. The solution structure of the Eu-terpyridyl complex with nitrate counterions is shown to have a similar arrangement of Eu3+ coordinating molecules as the crystal structure. This study illustrates how a combination of AIMD and EXAFS can be used to determine how ligands, solvent, and counterions coordinate with the lanthanide ions in solution.

Application study of curcumin fluorescent complex coated with pharmaceutical excipients for cell imaging.

Taking curcumin as the starting point, β-cyclodextrin was introduced on both sides, and lipid-soluble curcumin was coated by acrylic resin using oil-in-water strategy. Four different types of curcumin fluorescent complexes EPO-Curcumin (EPO-Cur), L100-55-Curcumin (L100-55-Cur), EPO -Curcumin-β-cyclodextrin (EPO-Cur-β-cd) and L100-55-Curcumin-β-cyclodextrin (L100-55-Cur-β-cd) were prepared to solve their own solubility and biocompatibility issues. The prepared curcumin fluorescent complexes were characterized and tested by spectroscopy. The characteristic peaks of 3446cm-1 (hydroxyl group), 1735cm-1(carbonyl group) and 1455cm-1 (aromatic group) were determined in the infrared spectrum. In the fluorescence emission spectrum, it was found that the emission intensity of different curcumin fluorescent complexes in polar solvents reached hundreds of times. Through the transmission electron microscopy shows that acrylic resin tightly coats curcumin into rods or clusters. In order to observe their compatibility with tumor cells more directly, live cell fluorescence imaging was carried out, and it was found that all four kinds of curcumin fluorescence complexes had good biocompatibility. In particular, the effect of EPO-Cur-β-cd and L100-55-Cur-β-cd is better than that of EPO-Cur and L100-55-Cur.

Photoswitchable Copper(I) and Copper(II) Complexes of Phenylazo‐3,5‐dimethylpyrazole Incorporated Ligands

AbstractWe report the design, synthesis, characterization, and photochemistry of three photoresponsive azoheteroarene‐based neutral N‐donor ligands. Furthermore, those bidentate and tridentate ligands have been coordinated with Cu(I) and Cu(II) metal ions to form seven complexes exhibiting different geometries and nuclearities. Detailed studies of the electronic properties, photoswitching, and thermal reverse isomerization behavior of the photoswitched states of the free ligands and their metal complexes in different solvents are presented.

Understanding the solvation structures of glyme-based electrolytes by machine learning molecular dynamics

Glyme-based electrolytes are of great interest for rechargeable lithium metal batteries due to their high stability, low vapor pressure, and non-flammability. Understanding the solvation structures of these electrolytes at the atomic level will facilitate the design of new electrolytes with novel properties. Recently, classical molecular dynamics (CMD) and ab initio molecular dynamics (AIMD) have been applied to investigate electrolytes with complex solvation structures. On one hand, CMD may not provide reliable results as it requires complex parameterization to ensure the accuracy of the classical force field. On the other hand, the time scale of AIMD is limited by the high cost of ab initio calculations, which causes that solvation structures from AIMD simulations depend on the initial configurations. In order to solve the dilemma, machine learning method is applied to accelerate AIMD, and its time scale can be extended dramatically. In this work, we present a computational study on the solvation structures of triglyme (G3) based electrolytes by using machine learning molecular dynamics (MLMD). Firstly, we investigate the effects of density functionals on the accuracy of machine learning potential (MLP), and find that PBE-D3 shows better accuracy compared to BLYP-D3. Then, the densities of electrolytes with different concentration of LiTFSI are computed with MLMD, which shows good agreement with experiments. By analyzing the solvation structures of 1 ns MLMD trajectories, we found that Li+ prefers to coordinate with a G3 and a TFSI− in equimolar electrolytes. Our work demonstrates the significance of long-time scale MLMD simulations for clarifying the chemistry of non-ideal electrolytes.

CRYSTAL AND MOLECULAR STRUCTURE OF THE ISLAND TETRANUCLEAR DIOXOMOLYBDENUM(VI) COMPLEX [MoO<sub>2</sub>(<i>L</i><sup>1</sup>)]<sub>4</sub> (H<sub>2</sub><i>L</i><sup>1</sup> IS ACETYLACETONE ISONICOTINOYLHYDRAZONE) WITH LARGE INTRA- AND INTERMOLECULAR CHANNELS

The solvated complex [МоО2(L1)]4dimethylformamide (I) was synthesized. Its structure wasdetermined by X-ray diffraction analysis. The crystal structure is composed of the tetranuclear complexes [МоО2(L1)]4 (Ia) as the structural units lying on crystallographic twofold axes. Both crystallographically independent molybdenum atoms are in a distorted octahedral coordination environment formed by two cis-О(oxo) ligands, two N(L1) atoms of two molecules Ia in trans positions to the О(oxo) ligands, and two О(L1) atoms of one complex molecule in cis positions to О(oxo) and trans to each other. Each (L1)2– ligand is coordinated to two Мо atoms in a tetradentate tridentate-chelating (2О, N) bridging (N) mode. The average bond lengths in complex Iа are as follows: Мо–О(oxo), 1.701 Å; Мо–N(L1), 2.460 (b) and 2.214 Å (c); Мо–О(L1), 1.980 Å. The О(oxo)–МоО–(oxo) bond angle is 105.6°. The ordered dimethylformamide molecule is located in a narrow channel in the structure. The strongly disordered (non-located) solvent molecules (methanol/dimethylformamide/water) occupy wide channels in the structure of I.

Electrocatalytic MOF‐Carbon Bridged Network Accelerates Li+‐Solvents Desolvation for High Li+ Diffusion toward Rapid Sulfur Redox Kinetics (Adv. Funct. Mater. 13/2023)

Electrocatalytic MOF-Carbon Bridged Network In article number 2212499, Meinan Liu, Cheng Yan, Jian Wang, and co-workers show an astronaut (Li+) in the spaceship (solvent molecules) representing Li+ ions with solvation sheath. When they come to an electronically and ionically conductive metal-organic framework modified with a carbon layer, astronauts can easily walk through these channels, which means a fast desolvation process of the Li+-solvents complex. Then these astronauts quickly catch polysulfides and complete the electrochemical reaction, indicating that the naked Li+ accelerates the conversions kinetics of sulfur species.

Cathodic co-reactant electrogenerated chemiluminescence of water-soluble heteroleptic iridium(III) complexes bearing N-methyl(pyridyl)pyridinium cyclometalating ligands

Heteroleptic iridium(III) complexes containing N-methyl-(2′-pyridyl)pyridinium cyclometalating ligands were examined as luminophores for cathodic electrogenerated chemiluminescence (ECL) with peroxydisulfate co-reactant. These water-soluble iridium(III) complexes exhibit reduction potentials that are far less negative than those of the archetypal tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) luminophore. As observed with tris(2,2′-bipyrazine)ruthenium(II) ([Ru(bpz)3]2+), these shifts in potential are favourable for cathodic ECL because they lower the oxidative quenching of the excited state, and improve the stability of the reduced metal complex in aqueous solvent. The ECL intensities increased with repeated scanning or pulsing of the applied potential, due to the deposition of the less-soluble reduced species at the electrode surface. Iridium(III) complex ‘Ir4’, which contains cyclometalating ligands derived from the 1-methyl-4-(2ʹ-pyridyl)pyridinium cation, produces ECL with peroxydisulfate co-reactant in aqueous solution that is far more intense than that of [Ru(bpy)3]2+, and comparable to [Ru(bpz)3]2+, but in contrast to the red emissions of the conventional ruthenium(II) complexes, the iridium(III) species exhibits green luminescence, creating opportunities for novel spectrally and potentially resolved ECL systems.

A Novel Type of Tetradentate Dipyridyl-Derived Bis(pyrazole) Ligands for Highly Efficient and Selective Extraction of Am3+ Over Eu3+ From HNO3 Solution

ABSTRACT The extraction of Am3+ and Eu3+ with 6,6’-bis(5-alkyl-1H-pyrazol-3-yl)-2,2’-bipyridine (BPzBPy, alkyl = i-Bu, n-Bu, n-Oct) from HNO3 medium and the complexation of BPzBPy with Eu3+ were investigated. By using meta-nitrobenzotrifluoride (F-3) as a diluent, iBu-BPzBPy ligand in combination with 2-bromohexanoic acid was able to extract Am3+ over Eu3+ with the nature of significantly high efficiency, relatively fast extraction kinetics, and easy stripping. Slope analysis showed the formation of a 1:2 metal/ligand extraction species. The analyses of electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared (FT-IR) and time-resolved laser fluorescence spectrum (TRLFS) revealed that the composition of the extracted complex was [Eu(H2O)L2]A3 (L = ligand; HA = 2-bromohexanoic acid). The complexation of iBu-BPzBPy ligand with Eu3+ was an enthalpy-driven spontaneous, exothermic, and entropy-decreasing process. Besides, the complex stability constants were also obtained via UV–vis spectrophotometric titration. Combining the results of solvent extraction and complexation studies, a cation exchange extraction model was also proposed.

Liquid Structures and Ion Dynamics of Ionic Liquids Viewed from Intermolecular Interactions.

The elucidation of the factors determining liquid structures and transport properties of ionic liquids is important for the design and development of ionic liquid electrolytes. This personal account introduces the importance of computational methods for studying ionic liquids. Molecular dynamics simulations provide detailed information on liquid structures of ionic liquid such as the structures of solvated cation complexes in equimolar mixtures of glymes and Li[TFSA] and the effects of the charges of electrode on liquid structure near the electrode. Ab initio calculations reveal that the magnitude of the attraction between ions and conformational flexibility ions play important roles in determining transport properties of ionic liquids. First principle molecular dynamics simulations elucidate why solvated cation complex is stable in the equimolar mixtures, although the Li+ -[TFSA]- interaction is greater than Li+ -glyme interaction.

Potentiometric Study of Complexation in a Copper(II)–1-Phenyl-2,3-dimethylpyrazoline-5-thione–Hydrochloric Acid–Acetone System

Potentiometry is used to study the formation of Cu(II)–1-phenyl-2,3-dimethylpyrazoline-5-thione (1-P-2,3-DMP-5-T) complex in a mixed solvent. The compositions of the complexes are determined, and their stepwise constants of stability are calculated. It is shown that when Cu(II) reacts with 1-P-2,3-DMP-5-T in a medium of mixed solvent HCl + acetone (10 : 1), quantities ΔH, ΔG, and ΔS have negative values at all stages.

High-Sensitivity Optical Fiber Photothermal Sensor for Antibiotic Detection With PDMS/Ti3CN MXene Composite Coating

Oxacillin sodium (OXS) is a typical antibiotic contaminant in water and belongs to the semi-synthetic penicillin category. OXS is toxic to human cells and may damage the immune system when it enters the human body. In this study, we propose an optical fiber sensor to detect antibiotic pollutants in water based on the photothermal effect of OXS with a polydimethylsiloxane (PDMS)/Ti3CN MXene composite-coated microfiber. The interaction between the evanescent field and OXS can be enhanced by the coated microfiber, which improves the sensor performance. Moreover, the coated microfiber can enhance the detection sensitivity owing to the high-thermo-optic coefficient of PDMS and the strong molecular adsorption of Ti3CN MXene. The results show that using the PDMS/Ti3CN MXene composite-coated microfiber, detection in the linear range of 0.02–0.1 mg/mL with a sensitivity of −761.39 nm/(mg/mL), and a detection limit of 26 ng/mL are achieved. Compared to that of an uncoated microfiber, the sensitivity of the composited-coated microfiber is improved by a factor of 6. The proposed sensor does not require solvent extraction or complex antibody preparation; therefore, it is easy to operate and exhibits high sensitivity. Furthermore, the sensor has potential applications in food safety and environmental pollutant detection.

Ethylene Polymerization with Thermally Robust Vanadium(III) Tris(2-pyridyl)borate Complexes

Despite the useful selectivity offered by vanadium catalysts for olefin polymerization, their implementation under practical conditions remains limited by poor productivity and thermal stability. This report describes phenyl tris(2-pyridyl)borate (Tpy–) complexes of vanadium(III) that are amenable to ethylene polymerization at temperatures approaching industrial conditions (>100 °C). We developed metal tris(2-pyridyl)borate precursors TpyLi, TpyK, and TpyAg, which undergo smooth metathesis with VCl3(THF)3 to provide solvated complexes TpyVCl2(DMF) and TpyVCl2(THF). In contrast, soft deprotonation of TpyH with triethylamine and VCl3(THF)3 gave the anionic complex [TpyVCl3][Et3NH], our optimal precatalyst. Thus, [TpyVCl3][Et3NH] polymerizes ethylene with low dispersity (∼2) and a moderate molecular weight (∼350000) at temperatures up to 135 °C. This work advances the use of tris(2-pyridyl)borates, an emerging ligand class, in catalysis and provides a platform for vanadium catalysis in demanding applications.

Iridium(III) solvent complex-based electrogenerated chemiluminescence and photoluminescence sensor array for the discrimination of bases in oligonucleotides

Development of rapid and sensitive method for the discrimination of bases in oligonucleotides is of great importance in clinical diagnosis. Here, we demonstrate the first case of single iridium(III) solvent complex-based electrogenerated chemiluminescence (ECL) and photoluminescence (PL) sensor array for the discrimination of bases in oligonucleotides. One iridium (III) solvent complex ([Ir(ppy)2(DMSO)Cl], ppy = 2-phenylpyridine, probe 1) was designed as both ECL and PL probe while five bases (guanine, adenine, cytosine, thymine and uracil) were chosen as analytes. Two-element sensor array was built for the discrimination of five bases based on the fingerprint response of probe 1 to bases via coordination interactions. The combination of unique ECL and PL variations with principal component analysis was applied for the quantitative analysis of five bases in a linear range of 1.0 μM–10 μM and for the effective discrimination of individual base, the mixture of bases and oligonucleotides. Moreover, the sensor array was successfully applied to discriminate different mismatched ss-DNAs from HIV gene (a fully-matched ss-DNA), even at single-base difference. This work demonstrates that the sensor array using single iridium (III) solvent complex is a promising approach for the discrimination of bases with good sensitivity and simpleness in clinical diagnosis.

Solvation-induced switching of the conformational state of alkoxy- and crown-substituted trisphthalocyaninates studied by UV-Vis and 1H-NMR spectroscopy

Solvation-induced switching between staggered and gauche conformers of europium(III) triple-decker complexes with [Formula: see text]-butoxy- and crown-substituted phthalocyanine ligands [(BuO)8Pc][Formula: see text]and [(15C5)4Pc][Formula: see text]was studied by UV-Vis and 1H-NMR in toluene and chloroform media. The crown-substituted complex Eu2[(15C5)4Pc]3 was conformationally invariant, adopting the staggered arrangement of adjacent ligands in both solvents. In contrast, in the case of butoxy-substituted complex Eu2[(BuO)8Pc]3, the staggered and gauche forms were stabilized in toluene and chloroform, respectively. These conclusions could easily be drawn from the UV-Vis data. In contrast, a comparison of the 1H-NMR spectra of the complexes in both solvents showed that the spectral manifestation of conformational switching was obscured by media effects, although some characteristic spectral patterns of each conformation could still be identified on the example of the complex with hexa-[Formula: see text]-butoxy-15-crown-5-phthalocyanine ligands Eu2[(BuO)6(15C5)Pc]3.

Electrochemically regulated luminescence of europium complexes with β-diketone in polyether matrices.

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu3+ and Eu2+. Initially, the intrinsically stable Eu3+ complex showed intense red photoluminescence (PL) induced by f-f transitions. After the electrochemical reduction of Eu3+ to Eu2+, broad blue PL was observed attributed to the d-f transitions in the Eu2+ complex. This distinct blue luminescence from the Eu2+ complex was attributed to the effective stabilization of the Eu2+ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices.

Improving performances of the electrode/electrolyte interface via the regulation of solvation complexes: a review and prospect.

The electrode/electrolyte interface (EEI) is a research hotspot in lithium-ion batteries, while the electrolyte solvation complex can be regarded as a factor that cannot be ignored in determining the performance of the EEI. From the perspective of the electrolyte solvation complex, this review summarizes the effects of solvation complexes on the composition of an EEI film and the Li+ desolvation process, and further clarifies the internal mechanism of the electrolyte composition controlling solvation chemistry. Finally, combined with doubtful points that are not comprehensively considered in the regulation of solvated complexes, this review puts forward some cutting-edge views, which are of great significance for future guidance in improving the performance of lithium-ion batteries.

Structural analysis and electronic properties of transition metal ions (Ni2+, Fe2+, Mn+ and Co+) with psoralen biomolecule as an anticancer drug

In the current research, the density functional theory (DFT) method is used to investigate the effects of cation-π interaction on complexes formed by psoralen drug with metal cations (Ni2+, Fe2+, Mn+ and Co+). The calculations are performed in the gas phase and the water and carbon tetrachloride (CCl4) solvents. The interactions generated in the complexes are analyzed using the atoms in molecules (AIM) and the natural bond orbital (NBO) approaches. The results indicate that the absolute amount of the binding energy of complexes in the polar solvent is less than the non-polar solvent while in the gas phase it is more than solution. The obtained data also show that with increasing polarity of the solvent, the stabilization energy of the complexes increases. To gain a better insight into the mentioned interactions, the descriptors of chemical reactivity such as energy gap, hardness, softness and electronic chemical potential are also explored. Our findings display that the studied complexes have high chemical stability and low chemical reactivity in the solution relative to the gas phase.

Structure–Dynamics Interrelation Governing Charge Transport in Cosolvated Acetonitrile/LiTFSI Solutions

Concentrated ionic solutions present a potential improvement for liquid electrolytes. However, their conductivity is limited by high viscosities, which can be attenuated via cosolvation. This study employs a series of experiments and molecular dynamics simulations to investigate how different cosolvents influence the local structure and charge transport in concentrated lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI)/acetonitrile solutions. Regardless of whether the cosolvent's dielectric constant is low (for toluene and dichloromethane), moderate (acetone), or high (methanol and water), they preserve the structural and dynamical features of the cosolvent-free precursor. However, the dissimilar effects of each case must be individually interpreted. Toluene and dichloromethane reduce the conductivity by narrowing the distribution of Li+-TFSI- interactions and increasing the activation energies for ionic motions. Methanol and water broaden the distributions of Li+-TFSI- interactions, replace acetonitrile in the Li+ solvation, and favor short-range Li+-Li+ interactions. Still, these cosolvents strongly interact with TFSI-, leading to conductivities lower than that predicted by the Nernst-Einstein relation. Finally, acetone preserves the ion-ion interactions from the cosolvent-free solution but forms large solvation complexes by joining acetonitrile in the Li+ solvation. We demonstrate that cosolvation affects conductivity beyond simply changing viscosity and provide fairly unexplored molecular-scale perspectives regarding structure/transport phenomena relation in concentrated ionic solutions.

QC and MD Modelling for Predicting the Electrochemical Stability Window of Electrolytes: New Estimating Algorithm

The electrolyte is an important component of lithium-ion batteries, especially when it comes to cycling high-voltage cathode materials. In this paper, we propose an algorithm for estimating both the oxidising and reducing potential of electrolytes using molecular dynamics and quantum chemistry techniques. This algorithm can help to determine the composition and structure of the solvate complexes formed when a salt is dissolved in a mixture of solvents. To develop and confirm the efficiency of the algorithm, LiBF4 solutions in binary mixtures of ethylene carbonate (EC)/dimethyl carbonate (DMC) and sulfolane (SL)/dimethyl carbonate (DMC) were studied. The structure and composition of the complexes formed in these systems were determined according to molecular dynamics. Quantum chemical estimation of the thermodynamic and oxidative stability of solvate complexes made it possible to establish which complexes make the most significant contribution to the electrochemical stability of the electrolyte system. This method can also be used to determine the additive value of the oxidation and reduction potentials of the electrolyte, along with the contribution of each complex to the overall stability of the electrolyte. Theoretical calculations were confirmed experimentally in the course of studying electrolytes by step-by-step polarisation using inert electrodes. Thus, the main aim of the study is to demonstrate the possibility of using the developed algorithm to select the optimal composition and solvent ratio to achieve predicted redox stability.