Complex Solvent Research Articles

Computational Exploration of the Impact of Low‐Spin and High‐Spin Ground State on the Chelating Ability of Dimethylglyoxime Ligand on Dihalo Transition Metal: A QTAIM, EDA, and CDA Analysis

ABSTRACTWe have explored the chelation of dimethylglyoxime ligand to divalent (ndx: x = 6, 7, 8) transition metal (TM) cations in two media (gas phase and water) at the B3LYP//LANL2DZ/6–311+G (d,p) and B3LYP/def2‐TZVP level at lower multiplicity and higher multiplicity states. Majority of the 18 optimized halide (chloride and bromide) complexes prefer square planar configuration. The correlations discerned between the experimental structural data and their estimated counterparts demonstrate a good credibility for complexes at lower multiplicity state. The basis set superposition errors (BSSEs) estimated is very small which reflects the fact that the choice of different basis sets (B3LYP//LANL2DZ/6–311+G (d,p)) introduces a slight bias in the calculation of energies. The ADMP (atom‐centered density matrix propagation) simulations in water on chloride complexes indicate the irreversible nature of these M—N dissociation in trajectory simulation process. This fact explains our exclusive focus on the examination of the [glyoxime ligand]…[MX2] interactions. In addition, the solvation of (3d and 4d) transition metal chloride complexes causes a sensitive augmentation of the metal ion affinity (MIA) with an average of 0.29 and 0.24 kcal/mol. In both multiplicity states, the topological parameters have illustrated that the M—N and M—X bonds are typical metal–ligand in both media. The average ΔEorb/ΔEsteric ratio equal to 0.45 and 0.11 in gas phase and water, respectively, reveals the predominance of the contributions from non‐covalent bonding interactions (NCI) compared to those of covalent bonding. But, the maximal value equal to 6.760 is obtained for bromide rhodium complex in water. NBO analysis in both media highlights the fact that a more pronounced ionic character is observed for the majority of the chloride complexes at both spin multiplicity states because of their higher retained charges on the metal atom. For [dimethylglyoxime]…[MX2] interaction (X = Cl and Br), the charge decomposition analysis demonstrates that the lowest value of the d/b ratio is found for the chloride platinum complex at lower multiplicity state in water. This is a proof of its strong relativistic effects.

Magnesium 4, 5, and 6 coordinate complexes with ligands bound via sp or sp2 hybridized atoms

As a metallic element of high natural abundance, magnesium finds a wide range of uses in both stoichiometric and more recently catalytic applications. This often takes advantage of the basic or nucleophilic properties of its compounds or their ability to co-complex with other organometallic compounds. However, the homoleptic chemistry of Mg(II) is heavily skewed towards alkyl and aryl ligands bound via sp2 and sp3 hybridized atoms. Here, we report our combined NMR spectroscopic and X-ray crystallographic study into much rarer alternative THF solvates of homoleptic magnesium complexes using ligands which bind via sp (alkynyl) and sp2 (imido) atoms. Specifically, we exploit the high acidity of terminal alkynes and diphenylacetonitrile to prepare tetra-solvated distorted octahedral complexes Mg(CCC6H4R-p)2(THF)4 (R = Me, CF3) and Mg(NCCPh2)2(THF)4 starting from the commercial alkyl reagent MgBu2. Adopting a similar deprotonative strategy using benzophenoneimine Ph2CNH affords the heteroleptic trinuclear complex Mg3(NCPh2)4nBu2(THF)2 with distorted tetrahedral Mg centres. Related imidomagnesium halide complexes can be accessed either by deprotonation of the imine with a Grignard reagent, or nucleophilic addition of a Grignard reagent to a nitrile, but these unusual five-coordinate complexes are unresponsive to a 1,4-dioxane induced Schlenk equilibrium shift. Employing a higher reflux temperature switching from a THF to a toluene medium permits access to the THF solvate of a homoleptic imido complex which also possesses a trinuclear constitution in Mg3(NCPh2)6(THF)2.

Structure and noncovalent interaction analysis of half-sandwich chiral-at-metal organoruthenium complexes with planar and η6-arene-metal axial chirality

The preparation of organometallic compounds has provided new molecular complexity in molecular science. The stereochemistry of organometallics has long been a great challenge due to the large atom radius and more valency. Herein, eight ruthenium piano-stool shaped Ru complexes 2a-d and 3a-d with η6-planar chirality and Ru-center chirality were successfully synthesized and resolved, and the absolute configurations were determined by X-ray diffraction analysis. Racemization experiment revealed the stability differences of the Ru complexes in various solvents. Furthermore, in asymmetric unit of complex 3b, there are two conformers bearing opposite η6-arene-Ru axial chirality. In the supramolecular organization, all of the Ru complexes are stabilized by hydrogen bonding, C-H···π and Cl/I···π interactions. π···π interaction was only observed in complex 3b. The Hirshfeld surface analysis and 2D fingerprint plot show that the eight complexes have a similar contribution composed of different noncovalent interactions to the stabilization of crystal packing. Interestingly, only complex 3b has 3.5% C···C interaction. The pairwise interaction energies were calculated using CE-B3LYP energy model and further visualized by 3D-energy framework, which show that the dominant interaction for all complexes is dispersion. Theoretical energies of each conformer of complex 2a-d and 3a-d with η6-arene rotated at different angles was calculated by DFT method, and the energy barrier between the two conformations was around 2-3 kcal/mol. Halide ligand exchange experiments on complex (SRu)-1a were performed and the plausible mechanism was proposed. These results have provided new evidence for the design of molecules with specific fine stereochemical information for potential applications in medicinal and material chemistry.

Photochemistry of a proton relay – system with triple fluorescence

The excited state of proton transfer and the dynamics of the excited states of three 3-carboxy substituted bis-salicylidenes (H4L1-3) have been studied by combining steady state and time-resolved absorption and emission methods, and with quantum chemical calculations. The 3-carboxy substituted bis-salicylidenes contain two coupled intramolecular hydrogen bonds of the OH…OH…N type. This system has two proton transfer sites. The compounds have excitation – dependent emission and a high sensitivity to the solvent polarity. ESIPT and deprotonation result in the co-existence of enol, keto, anionic and zwitterionic species with or without quinoid structure, whose emission bands are located from the blue to the yellowish-green region. The photophysical processes in the nano-to-microseconds timescale have been linked to the intermolecular interactions with the solvent, where hydrogen bonding leads to the formation of a cyclic 1:2 solute − solvent complex. Transient absorption spectroscopy revealed that the generation of charged structures of H4L1-3 occurs through a solvent-assisted proton transfer along the chain of two solvent molecules, which act as a proton-relay system. The computational study of the energy profiles and of the enol-to-keto tautomerization with explicit solvent molecules has been performed for the first time for this kind of ESIPT system.

Simulation of the non-adiabatic dynamics of an enone-Lewis acid complex in an explicit solvent.

Unlocking the full potential of Lewis acid catalysis for photochemical transformations requires a comprehensive understanding of the ultrafast dynamics of substrate-Lewis acid complexes. In a previous article [Peschel et al., Angew. Chem. Int. Ed., 2021, 60, 10155], time-resolved spectroscopy supported by static calculations revealed that the Lewis acid remains attached during the relaxation of the model complex cyclohexenone-BF3. In contrast to the experimental observation, surface-hopping dynamics in the gas phase predicted ultrafast heterolytic dissociation. We attributed the discrepancy to missing solvent interactions. Thus, in this work, we present an interface between the SHARC and FermiONs++ program packages, which enables us to investigate the ultrafast dynamics of cyclohexenone-BF3 in an explicit solvent environment. Our simulations demonstrate that the solvent prevents the dissociation of the complex, leading to an intriguing dissociation-reassociation mechanism. Comparing the dynamics with and without triplet states highlights their role in the relaxation process and shows that the Lewis acid inhibits intersystem crossing. These findings provide a clear picture of the relaxation process, which may aid in designing future Lewis acid catalysts for photochemical applications. They underscore that an explicit solvent model is required to describe relaxation processes in weakly bound states, as energy transfer to the solvent is crucial for the system to reach its minimum geometries.

Iridium(III) solvent complex-based electrogenerated chemiluminescence method for the detection of 3-methylhistidine in urine.

3-Methylhistidine (3-MeHis) is increasingly used as an indicator of muscle protein breakdown. The development of asensitive, simple, and non-invasive method for 3-MeHis assay is important in clinical practice. Herein, a sensitive, simple, and non-invasive electrogenerated chemiluminescence (ECL) method was proposed for the quantitation of 3-MeHis in urine by using an iridium(III) solvent complex ([Ir(dfppy)2(DMSO)Cl], dfppy = 2-(2,4-difluorophenyl)pyridine, Ir-DMSO) as a signal reagent. The photoluminescence (PL) and ECL responses of Ir-DMSO to 3-MeHis were studied. The ECL intensity of Ir-DMSO was enhanced in the presence of 3-MeHis because of the coordination recognition between Ir-DMSO and the imidazole group of 3-MeHis. Based on the enhancement of ECL intensity, 3-MeHis can be sensitively detected in the range of 5 to 25μM. The detection limit was 0.4μM. This is the first report of an ECL method for the quantitation of 3-MeHis. Further, to investigate the feasibility of the Ir-DMSO-based ECL method in practical applications, the developed ECL method was applied for 3-MeHis assay in urine samples of 28 healthy volunteers and 2 patients. The urine samples from patients hospitalized with obesity and kidney disease and healthy individuals were distinguished by the ECL responses of Ir-DMSO. The proposed ECL method based on the coordination recognition between iridium(III) solvent complex and the imidazole group of 3-MeHis allows inexpensive, fast, non-invasive, and sensitive detection of 3-MeHis in urine, which is promising for assessing large volumes of patients for routine analysis in clinical practices.

(Invited) Design Criteria of Ether Electrolytes and Stable Interphase Toward Reversible Intercalation Chemistry of Graphite Anode in Li-Ion Batteries

To date, it is extensively believed that ether electrolytes are incompatible with graphite anode in Li-ion batteries due to detrimental solvent co-intercalation and exfoliation. Here, we provide design criteria of ether electrolytes for reversible graphite anode without the high salt concentration. In short, for ether electrolytes, the reductive stability of anions (or their solvated complex) and the solid-electrolyte interphase (SEI) govern the reversibility of graphite anode. Exfoliation and co-intercalation are not the root cause of as-documented cell failures using graphite anodes. While reductive-instable lithium bis(fluorosulfonyl)imide (LiFSI) is the optimal salt paired with DOL, reductive-stable LiBF4 finds applications with DME. Individual 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) based electrolytes can enable ~99.9% Coulombic efficiency with excellent capacity retention and fast-charge capability using natural graphite. In DOL electrolytes, weakened Li-solvent interaction and preferential reduction of FSI anion coordinated with Li-ion contribute to homogeneous SEI enriched with inorganic species, for example, LiF. Therefore, electrolyte reduction and Li-DOL co-intercalation are inhibited. In DME electrolytes, we show that LiBF4 has limited reduction, majorly on the edge site. We discover that a self-terminating, heterogeneous interphase based on grainy LiF proves to be desirable for operating Li-solvent co-intercalation. Taking advantage of the anisotropic characteristics of natural graphite, we conducted a holistic investigation into the nature, function, and formation of the heterogeneous SEI. In these studies, we clarify a long-lasting confusing issue in LIBs community-that is, the compatibility between ether electrolytes and graphite anode. Our findings not only shed light on the enigmatic interphase formed by ether electrolytes but also offer critical insights into future electrolyte design for graphite anodes operated under extreme conditions.

(Digital Presentation) Physical and Chemical Properties of Lithium Tetrachloroaluminate Monosolvate with Sulfur Dioxide

In connection with the expansion of the areas of application of lithium-ion batteries and the increase in their energy characteristics, researchers are increasingly paying attention to the problems of battery safety. The use of non-flammable electrolyte systems will significantly improve the safety of lithium-ion batteries.Electrolyte systems based on solvate complexes of sulfur dioxide have high electrical conductivity and are non-flammable [1]. The most studied composition is LiAlCl4 × 1.6 SO2 [1] and LiAlCl4 × 3 SO2 [2]. The properties of LiAlCl4 x SO2 monosolvate have not been described in the literature.The presented work summarizes the results of studies of the physicochemical properties (electrical conductivity, viscosity, density) of lithium tetrachloroaluminate monosolvate with sulfur dioxide (table). The temperature dependences of viscosity, density and electrical conductivity are presented in the figure.This work was performed as part of the Ministry of Science and Higher Education of the Russian Federation [Government Order Theme No. 121111900148-3]. References Hartl, R., Fleischmann, M., Gschwind, R., Winter, M., & Gores, H. (2013). A Liquid Inorganic Electrolyte Showing an Unusually High Lithium-Ion Transference Number: A Concentrated Solution of LiAlCl4 in Sulfur Dioxide. Energies, 6(9), 4448–4464. DOI:10.3390/en6094448Chul Wan Park, & Oh, S. M. (1997). Performances of Li/LixCoO2 cells in LiAlCl4 · 3SO2 electrolyte. Journal of Power Sources, 68(2), 338–343. DOI:10.1016/s0378-7753(97)02518-4 Figure 1

Transformations in phenylboronic acid at high pressures and temperatures

A recent report on obtaining the n-type conductivity in diamonds doped with boron–oxygen complexes in a metal solvent (X. Liu et al., PNAS 2019) stimulates interest in the synthesis of diamonds in heterohydrocarbon systems with oxygen and boron. The simultaneous effect of boron and oxygen heteroatoms on phase transitions in a hydrocarbon system is examined in phenylboronic acid C6H5B(OH)2 at pressures of 7–8.5 GPa and temperatures up to 1600 °C. At pressures of about 7 GPa and temperatures up to 1100 °C, the transformation of the precursor occurs through the stage of polymerization into a graphane-like phase with the subsequent formation of nanographite. Micro- and nanodiamonds are synthesized at 8.5 GPa and 1600 °C from the initial precursor and nanographite, which is a product of preliminary carbonization, respectively. Despite the presence of oxygen and boron in the growth system, the n-type conductivity in diamonds and nanographite is not detected. It is found that the degree of boron doping of diamond in hydrocarbon systems decreases in the presence of oxygen with a high chemical affinity to boron and that nanodiamonds in the carbonized product can be obtained when volatile components leave the system.

Optical Rotation Predictions for Rigid Chiral Solute-Achiral Solvent 1:1 Complexes with the PCM Model

We computed specific optical rotations (ORs) in solution for forty-two solute–solvent combinations, involving seventeen chiral solutes and eight achiral solvents, using cam-B3LYP/aug-cc-PVTZ. Explicit solvent effects were considered by calculating Boltzmann-averaged ORs from multiple conformers of a 1:1 solute–solvent complex, with additional implicit solvation. The PCM solvation model correctly predicted OR signs for all combinations, while the “1:1 complex plus PCM“ schemes misjudged it in two cases. Norbornenone in cyclohexane displayed the largest absolute deviation, indicating an inadequate description of the cam-B3LYP functional’s delocalized electronic structure. Incorrect OR signs for fenchone in methanol with the ”1:1 complex plus PCM“ schemes underscored the limitations of our simplistic scheme, which incorporates explicit effects by averaging one-to-one interactions between solute and solvent. Considering computational costs, the ”1:1 complex plus PCM“ scheme may not be the optimal choice for our test set, as the PCM model alone suffices for accurate specific OR calculations in solution.

Synthesis, characterization and evaluation of new anti-inflammatory iron charge transfer complexes

The novelty and the essential purpose of this research is the preparation of new anti-inflammatory iron complexes in water green solvent using critical micelle concentration of anionic surface active agent (SAA). Three new anti-inflammatory iron complexes have been prepared. Thiophene-electron (es) donor (D) Schiff base (2-(2-OH-benzylidene)-amino)-4, 5, 6, 7-tetrah ydrobenzo[b] thiophene-3-carbonitrile) has been prepared. Molecular structures of all samples were confirmed based on CNH analysis, 1H NMR and 13C NMR spectra. The molecular structure of Schiff base is further confirmed by computational chemistry using the DFT-B3LYP method, 6-31G (d) basis set. Observed and simulated 1H NMR, UV–Vis. IR/Raman spectra confirmed the molecular structure of D. This Schiff base is intercalated to ferric chloride (FeCl3) giving pure iron charge transfer complex (CTCs). In vitro and kinetic studies confirmed Fe-CTC complexes had (concentration-dependent) potent antimicrobial-, good anti-inflammatory activities. Free radical scavenging activity nitrous oxide (NO.) of Fe (III)CTCs is attributed to geometry Fe(III) ions as distorted octahedral (either monoclinic or triclinic single crystals) via functional groups (-C]N–O, NH2). Elemental analysis and EDS spectra confirmed strong binding between iron and hetero atoms (N, S, O) of D molecules.

Synthesis of Cd (II), Fe (III), Cu (II), and Cr (VI) complexes of Schiff bases and their antibacterial activities

Schiff base and the metal derivatives have been utilized in numerous areas of the economy. Synthesis and antibacterial activities of Cd (II), Cr (VI), Cu (II), and Fe (III) complexes of Schiff bases were evaluated in this work. Complexes synthesized were Bis(1-phenyl-3-methyl-4-Phenyl acetyl 5-pyrazolone)Cadmium (II) (Cd(HPMPP)2), Tris(1-phenyl-3-methyl-4-benzoyl-5-pyrazolone)Iron(III)(Fe(HPMBP)3), Bis(1-phenyl-3-methyl-4-phenylacetyl-5-pyrazolone)Copper (II) (Cu(HPMPP)2), Hexakis(1-phenyl-3-methyl-4-palmitoyl-5-pyrazolone)Chromium (VI) (Cr(HPMPP)6), and Tris(1-phenyl-3-methyl-4- palmitoyl-5-pyrazolone)Iron (III) (Fe(HPMPP)3). The physical state, colour, and melting point of these complexes were determined using appropriate analytical techniques. Results showed that all the complexes were crystalline in nature; their colours were variable, while their melting points were sharp. The solubility of these complexes in deionized water, acetone, methanol, and ethanol was also carried out. The outcome revealed that all the metal complexes were insoluble in deionized water, Cr(HPMPP)6 was soluble in acetone, methanol, and ethanol. However, the solubility of other metal complexes in the organic solvents used was variable. The antibacterial activities of these metal complexes at different concentrations were also tested against distilled water, E. coli, S. aureus, B. subtillus, and S. typhi. The results showed that, antimicrobial activity of these complexes against distilled water was negative whereas, the bacterial growth of all the bacteria was inhibited by the complexes though at different rates. The inhibition rate of microorganisms was inversely proportional to the concentration of the complexes. The antibacterial activities of Cd(HPMPP)2 and Cr(HPMPP)6 were outstanding against the growth of all the bacteria. Thus, a proper processing of these complexes might result in excellent antibacterial drugs. However, more studies on the mode of action of these complexes against microorganisms and their toxicity should be done in order to establish their potentials for pharmaceutical applications.

Inclusion of Anion Additives in the Inner Solvation Shell to Regulate the Composition of Solid Electrolyte Interphase

AbstractAn innovative approach to electrolyte engineering in carbonate electrolytes is introduced by incorporating high donor number dual anion additives into the conventional electrolyte system (1 M NaPF6 EC:PC). The active engagement of anions in the primary solvation shell effectively hinders the reduction of solvent molecules by reducing the Lowest Unoccupied Molecular Orbital (LUMO) of Na+‐solvent‐anion complex as compared to the LUMO of pure solvents or Na+‐solvent complex. The participation of anions leads to the formation of a thinner and an inorganic‐rich Solid Electrolyte Interphase on the hard carbon anode enhancing Initial Coulombic Efficiency and significantly improving its kinetics. Moreover, the system with dual anion additives exhibits oxidative stability up to 4.5 V, effectively mitigating the undesired side reactions at high voltage operation of the layered sodium nickel manganese oxide cathode. The addition of dual anion additives proves instrumental in suppressing structural degradation and transition metal dissolution during the long cycling performance of the layered oxide cathode in a sodium‐ion full cell. The synergistic effects of this dual anion additive added electrolyte on both the anode and the cathode ultimately ensured prolonged cycling of the sodium‐ion full cell. The electrolyte engineering approach outlined in this study opens the door to advancing next‐generation high‐voltage sodium batteries.

Coordinated Solvent Molecules Enable the Excellent Capabilities of Two Zn2+‐Based Complexes in Detecting l‐Arginine via Long‐Lived Luminescence Recovery

AbstractLuminescence metal–organic materials (MOMs) are widely used as probes for detection. However, most of such probes are based on fluorescence and work in either turn‐off or turn‐on mode. In contrast, long‐lived (>10 ms) probes (LLPs) with recovery response to analyte are quite rare. Herein “solvation complex” strategy is used to prepare two new afterglow complexes with multiple coordinated solvents, trans‐complex 1 with both delayed fluorescence (DF) and room temperature phosphorescence (RTP), and cis‐complex 2 with RTP. Remarkably, they can serve as selective and recovery LLPs for l‐Arginine detection, with limit of detection down to 1.0 × 10−7 M. In addition, heating/fumigation can induce reversible arousal/silence of their afterglow, while H2O/DMSO vapor fumigation causes reversible crystalline‐to‐crystalline transformation between them. Detailed mechanism studies reveal that the change in coordinated solvent, including loss/acquisition, exchange, or replacement, plays a key role in such afterglow multi‐stimuli‐responsive properties. This work not only shows the potential of such long‐lived luminescence complex for recovery detection, but also reveals the unique advantages of solvation complex in the preparation of afterglow multi‐stimuli‐responsive materials

Linear, Electron-Rich Erbium Single-Molecule Magnet with Dibenzocyclooctatetraene Ligands.

Judicious design of ligand scaffolds to highly anisotropic lanthanide ions led to substantial advances in molecular spintronics and single-molecule magnetism. Erbium-based single-molecule magnets (SMMs) are rare, which is attributed to the prolate-shaped ErIII ion requiring an equatorial ligand field for enhancing its single-ion magnetic anisotropy. Here, we present an electron-rich mononuclear Er SMM, [K(crypt-222)][Er(dbCOT)2], 1 (where dbCOT = dibenzocyclooctatetraene), that was obtained from a salt metathesis reaction of ErCl3 and K2dbCOT. The dipotassium salt, K2dbCOT, was generated through a two-electron reduction of the bare dbCOT0 ligand employing potassium graphite and was crystallized from DME to give the new solvated complex, [K(DME)]2[dbCOT]n, 2. 1 was analyzed through crystallography, electrochemistry, spectroscopy, magnetometry, and CASSCF calculations. The structure of 1 consists of an anionic metallocene complex featuring a linear (180.0°) geometry with an ErIII ion sandwiched between dianionic dbCOT ligands and an outer-sphere K+ ion encapsulated in 2.2.2-cryptand. Two pronounced redox events at negative potentials allude to the formation of a trianionic erbocene complex, [Er(dbCOT)2]3-, on the electrochemical time scale. 1 shows slow magnetic relaxation with an effective spin-reversal barrier of Ueff = 114(2) cm-1, which is close in magnitude to the calculated energies of the first and second excited states of 96.9 and 109.13 cm-1, respectively. 1 exhibits waist-constricted hysteresis loops below 4 K and constitutes the first example of an erbocene-SMM bearing fused aromatic rings to the central COT ligand. Notably, 1 comprises the largest COT scaffold implemented in erbocene SMMs, yielding the most electron-rich homoleptic erbium metallocene SMM.

Accelerating Computation of Acidity Constants and Redox Potentials for Aqueous Organic Redox Flow Batteries by Machine Learning Potential-Based Molecular Dynamics.

Due to the increased concern about energy and environmental issues, significant attention has been paid to the development of large-scale energy storage devices to facilitate the utilization of clean energy sources. The redox flow battery (RFB) is one of the most promising systems. Recently, the high cost of transition-metal complex-based RFB has promoted the development of aqueous RFBs with redox-active organic molecules. To expand the working voltage, computational chemistry has been applied to search for organic molecules with lower or higher redox potentials. However, redox potential computation based on implicit solvation models would be challenging due to difficulty in parametrization when considering the complex solvation of supporting electrolytes. Besides, although ab initio molecular dynamics (AIMD) describes the supporting electrolytes with the same level of electronic structure theory as the redox couple, the application is impeded by the high computation costs. Recently, machine learning molecular dynamics (MLMD) has been illustrated to accelerate AIMD by several orders of magnitude without sacrificing the accuracy. It has been established that redox potentials can be computed by MLMD with two separated machine learning potentials (MLPs) for reactant and product states, which is redundant and inefficient. In this work, an automated workflow is developed to construct a universal MLP for both states, which can compute the redox potentials or acidity constants of redox-active organic molecules more efficiently. Furthermore, the predicted redox potentials can be evaluated at the hybrid functional level with much lower costs, which would facilitate the design of aqueous organic RFBs.

Solvent-Mediated Hetero/Homo-Phase Crystallization of Copper Nanoclusters and Superatomic Kernel-Related NIR Phosphorescence.

Atomically precise superatomic copper nanoclusters (Cu NCs) have been the subject of immense interest for their intriguing structures and diverse properties; nonetheless, the variable oxidation state of copper ions and complex solvation effects in wet synthesis systems pose significant challenges for comprehending their synthesis and crystallization mechanism. Herein, we present a solvent-mediated approach for the synthesis of two Cu NCs, namely, superatomic Cu26 and pure-Cu(I) Cu16. They initially formed as a hetero-phase and then separated as a homo-phase via modulating binary solvent composition. In situ UV/vis absorption and electrospray ionization mass spectra revealed that the solvent-mediated assembly was determined to be the underlying mechanism of hetero/homo-phase crystallization. Cu26 is a 2-electron superatom with a kernel-shell structure that includes a [Cu20Se12]4- shell and [Cu6]4+ kernel, containing two 1S jellium electrons. Conversely, Cu16 is a pure-Cu(I) Cu/Se nanocluster that features a [Cu16Se6]4+ core protected by extra dimercaptomaleonitrile ligands. Remarkably, Cu26 exhibits unique near-infrared phosphorescence (NIR PH) at 933 nm due to the presence of a superatomic kernel-related charge transfer state (3MM(Cu)CT). Overall, this work not only showcases the hetero/homo-phase crystallization of Cu NCs driven by a solvent-mediated assembly mechanism but also enables the rare occurrence of NIR PH within the 2-electron copper superatom family.

Revealing electrochemical behavior for high-quality and efficient bismuth deposition

Methanesulfonic acid (MSA, CH3SO3H) emerges as a sustainable and stable medium for membrane-assisted electrodeposition in bismuth (Bi) recovery. The incorporation of calcium lignosulfonate (CL) within the MSA-based system markedly improves the electrodeposition quality and efficiency of Bi, although the exact electrochemical mechanism and kinetics of CL's influence remains unclear and warrant further investigation. Our study focuses on the impact of CL on the electrochemical behavior through quantum chemical calculations, molecular dynamics simulations, electrochemical analyses and in-situ electrochemical optical microscopy. Within the primary solvation shell, Bi3+ associates closely with water and CH3SO3− ions, while CL is embedded in the secondary shell, forming a complex interaction network with Bi3+, H2O, and CH3SO3−, culminating in a solvation complex of Bi(CH3SO3)1.68·0.02CL·6·72H2O. This complex disrupts intra-solution hydrogen bonding, reduces water activity and undesirable side reactions, and thus promotes the electrodeposition efficiency. At the cathode's double electric layer, de-solvated Bi(CH3SO3)2+·nH2O ions are preferentially discharged and reduced. The pronounced physical adsorption of CL at the interface facilitates a three-dimensional electro-crystallization nucleation and growth process, yielding a uniform, smooth, and compact Bi deposit. Our findings not only extend the electrochemical understanding but also provide practical insights for optimizing Bi recovery in the CL-MSA system, with implications for the electrochemical recovery of other metals like lead and tin.

Unveiling Mechanistic Complexity in Manganese-Catalyzed C-H Bond Functionalization Using IR Spectroscopy Over 16 Orders of Magnitude in Time.

ConspectusAn understanding of the mechanistic processes that underpin reactions catalyzed by 3d transition metals is vital for their development as potential replacements for scarce platinum group metals. However, this is a significant challenge because of the tendency of 3d metals to undergo mechanistically diverse pathways when compared with their heavier congeners, often as a consequence of one-electron transfer reactions and/or intrinsically weaker metal-ligand bonds. We have developed and implemented a new methodology to illuminate the pathways that underpin C-H bond functionalization pathways in reactions catalyzed by Mn-carbonyl compounds. By integrating measurements performed on catalytic reactions with in situ reaction monitoring and state-of-the-art ultrafast spectroscopic methods, unique insight into the mode of action and fate of the catalyst have been obtained.Using a combination of time-resolved spectroscopy and in situ low-temperature NMR studies, we have shown that photolysis of manganese-carbonyl precatalysts results in rapid (<5 ps) CO dissociation─the same process that occurs under thermal catalytic conditions. This enabled the detection of the key states relevant to catalysis, including solvent and alkyne complexes and their resulting transformation into manganacycles, which results from a migratory insertion reaction into the Mn-C bond. By systematic variation of the substrates (many of which are real-world structurally diverse substrates and not simple benchmark systems) and quantification of the resulting rate constants for the insertion step, a universal model for this migratory insertion process has been developed. The time-resolved spectroscopic method gave insight into fundamental mechanistic pathways underpinning other aspects of modern synthetic chemistry. The most notable was the first direct experimental observation of the concerted metalation deprotonation (CMD) mechanism through which carboxylate groups are able to mediate C-H bond activation at a metal center. This step underpins a host of important synthetic applications. This study demonstrated how the time-resolved multiple probe spectroscopy (TRMPS) method enables the observation of mechanistic process occurring on time scales from several picoseconds through to μs in a single experiment, thereby allowing the sequential observation of solvation, ligand substitution, migratory insertion, and ultimate protonation of a Mn-C bond.These studies have been complemented by an investigation of the "in reaction flask" catalyst behavior, which has provided additional insight into new pathways for precatalyst activation, including evidence that alkyne C-H bond activation may occur before heterocycle activation. Crucial insight into the fate of the catalyst species showed that excess water played a key role in deactivation to give higher-order hydroxyl-bridged manganese carbonyl clusters, which were independently found to be inactive. Traditional in situ IR and NMR spectroscopic analysis on the second time scale bridges the gap to the analysis of real catalytic reaction systems. As a whole, this work has provided unprecedented insight into the processes underpinning manganese-catalyzed reactions spanning 16 orders of magnitude in time.

The Preferential Solvation of Methyl Red in Various Binary Aqueous Solutions: Solvatochromism, Preferential Solvation Parameters, Microheterogeneity of Solvents and Polarity Scale.

The solvatochromic characteristics of methyl red were examined in several aqueous solutions from pure water, with methanol, ethanol, propanol, acetonitrile, and dioxane. In order to explain the preferred solvation of the probe azo dye in the binary mixed solvents, the solvent exchange model of Bosch and Roses was used to evaluate the association between the empirical solvent polarity scale (ET) values of MR and solvent composition. Non-linear solvatochromism of methyl red was noted in all aqueous mixtures containing methanol, ethanol, propanol, acetonitrile, and dioxane. In addition to calculating the local mole fraction of each solvent composition in the cybotactic area of the probe, the impact of the solvating shell composition on the preferential solvation of the solute dye was examined in terms of both solvent-solvent and solute-solvent interactions. The local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. The results indicated that the MR solvation shell was thoroughly saturated with the solvent complex S12 in the following order: dioxane > ethanol > methanol > acetonitrile > propanol. Data from the binary systems were analyzed with KAT parameters using a multi-model; in aqueous methanol and ethanol solutions, the hydrogen acidity was more responsible for the spectral shift, whereas in aqueous acetonitrile and dioxane solutions, the basicity has a greater influence.