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The Li–O2/CO2 battery with high capacity has recently been proposed as a new protocol to convert CO2. However, the fundamental mechanism for the reaction still remains hazy. Here, we investigated the discharge processes of Li–O2/CO2 (70%/30%) batteries in two solvents, dimethyl sulfoxide (DMSO) and 1,2-dimethoxyethane (DME). During discharge, both solvents initially show the reduction of oxygen. However, afterward, the solvent affects the reaction pathways of superoxide species by solvating Li+ with different strength, depending on the so-called donor number. More precisely, the initial formation of CO4•– is favored in DMSO at the expense of lithium superoxide formation that we observed in DME. Despite the different intermediate processes, X-ray diffraction showed that Li2CO3 was the final discharge product in both solvents. Moreover, we observed that CO2 cannot be reduced within the electrochemical stability window of DMSO and DME.

The electrochemical oxidation of aniline dimers (4-aminodiphenylamine and 2-aminodiphenylamine) was studied at a glassy carbon electrode in hydrophobic and hydrophilic aprotic solvents and also in ethanol as a neutral amphiprotic solvent. In these solvents, both isomers, show the proton coupled electron transfer mechanism. A linear relationship between the redox potential of these molecules and the donor number of the studied solvents has been found. Our data show that both dynamics of solvent reorientation and the structure of aniline dimer, have a role in the heterogeneous electron transfer rate constant of 4-aminodiphenylamine and 2-aminodiphenylamine. A near linear relationship between the heterogeneous standard rate constant (log k s ) and the longitudinal relaxation time (log τ L ) of the solvents has been found. Furthermore, the mechanism of oxidation of aniline dimers has also been investigated using the rotating disk electrode technique, and the parameters such as heterogeneous rate constant and diffusion coefficient have been determined from Koutecky-Levich plot.

High donor number (DN) solvents in Li-O2 batteries that dissolve superoxide intermediates in lithium peroxide (Li2 O2 ) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li-O2 batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)3 ) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)3 integrates with the superoxide intermediate, accelerating O2 reduction kinetics and reducing side reactions. During charge, V(acac)3 acts as a redox mediator that permits efficient oxidation of Li2 O2 . The cells with V(acac)3 exhibit low overpotential, high rate performance, and considerable cycle stability.

The results of a potentiometric and calorimetric study on the complexation reactions of neutral N-donor ligands 1,4-diaminobutane (dab) and 1,5-diaminopentane (dap) with silver(I) in dimethylsulfoxide (DMSO) are reported. The investigation is extended for dab ligand to the aprotic solvent acetonitrile (AN), which presents quite different dielectric constant and donor number with respect to DMSO. In both solvents, polynuclear Ag2L22+ and Ag2L32+ species of high stability are formed, which inhibit the formation of mononuclear ones. The Ag2L22+ species are stabilized by the formation of large, stable non-chelate cyclic rings whose structures are described by DFT calculations. The overall enthalpy terms associated with the complex formation are strongly exothermic, whereas entropy values oppose the complex formation. An interesting feature is the little enthalpy and no significant or positive entropy variation associated with the successive formation of Ag2L32+. Also in this case, molecular modeling studies shed some light on their structure in solution, indicating that probably no changes of configuration around the metal ion occur. The stability constants and enthalpy values obtained for common Ag2L22+ species are slightly influenced by the chain length of the diamines, as confirmed also by a comparison with available data for the same species formed by the shorter 1,3-diamino propane (dapr) in DMSO.

Nano-composite polymer gel electrolytes were synthesized by using polyethylene oxide (PEO), ammonium tetrafluoroborate (NH4BF4), fumed silica (SiO2), dimethylacetamide (DMA), ethylene carbonate (EC), and propylene carbonate (PC) and characterized by conductivity studies. The effect of donor number of solvent on ionic conductivity of polymer gel electrolytes has been studied. The mechanical strength of the gel electrolytes has been increased with the addition of nano-sized fumed silica along with an enhancement in conductivity. Maximum room temperature ionic conductivity of 2.63 × 10−3 and 2.92 × 10−3 S/cm has been observed for nano-composite gel electrolytes containing 0.1 and 0.5 wt% SiO2 in DMA+1 M NH4BF4+10 wt% PEO, respectively. Nano-composite polymer gel electrolytes having DMA have been found to be thermally and electrically stable over 0 to 90 °C temperature range. Also, the change in conductivity with the passage of time is very small, which may be desirable to make applicable for various smart devices.

Effect of the solvent nature on the kinetics of photoreduction of 3,6-di-tert-butyl-1,2-benzoquinone and its six derivatives in the presence of N,N-dimethylaniline and 4-(N,N-dimethylamino)benzaldehyde has been investigated. It has been found that for the о-quinone—amine pair, for which the free energy change of electron transfer is ΔGe > +0.11 eV, the rate constant of о-quinone photoreduction kH decreases proportionally to the increase in the acceptor number of the solvent. For the о-quinone—amine pair with ΔGe < +0.11 eV, the kH value decreases proportionally to the increase in the donor number of the solvent. It has been established that the enhancement of the electron-acceptor properties of the solvent leads to the emergence of kinetic isotope effect for the reactant pairs of 3,6-di-tert-butyl-1,2-benzoquinone and 4,5-dimethoxy-3,6-di-tert-butyl-1,2-benzoquinone with N,N-di-methylaniline (ΔGe = +0.11 and +0.22 eV, respectively).

We report an experimental study on the effect of solvents on the model SN Ar reaction between 1-chloro-2,4-dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf2 (-) , DCN(-) , SCN(-) , CF3 SO3 (-) , PF6 (-) , and FAP(-) with the series of cations 1-butyl-3-methyl-imidazolium ([BMIM](+) ), 1-ethyl-3-methyl-imidazolium ([EMIM](+) ), 1-butyl-2,3-dimethyl-imidazolium ([BM2 IM](+) ), and 1-butyl-1-methyl-pyrrolidinium ([BMPyr](+) ). The observed solvent effects can be attributed to an "anion effect". The anion effect appears related to the anion size (polarizability) and their hydrogen-bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.

The near-infrared (NIR) absorption properties of a square-planar nickel–dithiolene complex [Ni(iPr2timdt)2] in various organic solvents have been investigated (iPr2timdt denotes a monoanion of 1,3-diisopropylimidazolidine-2,4,5-trithione). In non-coordinating aprotic organic solvents of smaller relative permittivity (er < 10) such as dichloromethane (er = 8.9), the neutral complex [Ni(iPr2timdt)2]0 shows a huge and sharp NIR absorption band at ca. 1000 nm having the molar absorptivity of e = 6–8 × 104 L mol−1 cm−1. In contrast, in strongly coordinating solvents such as pyridine (Gutmann’s donor number, DN = 33.1), the NIR absorption of [Ni(iPr2timdt)2]0 disappears most probably, owing to the coordination of pyridine molecules onto the axial sites of this square-planar complex. In high relative permittivity solvents such as N,N-dimethylformamide (DMF, er = 36.71), [Ni(iPr2timdt)2]0 (λmax: ca. 1000 nm) undergoes spontaneous reduction reactions yielding the ionic complexes of [Ni(iPr2timdt)2]− (λmax: ca. 140...

We reported previously that ionic liquids containing cationic solvatochromic metal–chelate complexes exhibit vapochromic and solvatochromic properties, changing color upon coordination of different solvents. To control the solvent response by intramolecular coordination, an ether side chain was introduced into the cation as an additional flexible coordination site, and ionic liquids of the formula [Cu(acac){Me2NCH2CH2NMe(CH2)nOMe}][Tf2N] {[1][Tf2N]: n = 3, [2][Tf2N]: n = 4; acac = acetylacetonato, Tf2N = (F3CSO2)2N–} were synthesized. The melting points of [1][Tf2N] and [2][Tf2N] were 44.1 °C and 49.8 °C, respectively. X-ray crystal-structure determination revealed intramolecular coordination of the side chain in [1][Tf2N] and its absence in [2][Tf2N] in the solid state. The addition of 1 and 2 mol-equiv. of dimethyl sulfoxide to [1][Tf2N] produced ionic liquids with Tm = 28.6 °C and –12.0 °C, respectively. To investigate the potential competition between side-chain coordination and solvent coordination, the solvatochromism of these salts was investigated in various solvents. Although the d–d transition energy of [2][Tf2N] varies linearly with the donor number (DN) of a solvent, that of [1][Tf2N] is nearly constant in solvents with a DN smaller than that of methanol owing to intramolecular coordination. This demonstrates the control of solvent response by intramolecular coordination sites.

The therrmodynamic parameters and equilibrium constant of displacement of dimethy sulfide by 3-carboaldehyde pyridine as N-donor ligand in cis-[Pt(4-MeC6H4)2(SMe2)2] complex have been measured using UV vis spectroscopy in acetone, dichloromethane and benzene at various temperatures (T=15-20 °C) and compared with previous my reported about similar reaction. ΔHo (KJ.mol-1) of the mentioned reaction in acetone has been 7.158 while obtained less in dichloromethane (4.109 ) and more in benzene(9.96). The entropy of the reaction has been obtained 86.86 J.mol-1.K-1 in acetone , while calculated less in CH2Cl2 (73.29 J.mol-1.K-1) and more in last solvent (97.40 J.mol-1.K-1). Also, the Gibbs energy, ΔG (J.mol-1), of the reaction obtained -18738.79, -17741.55 and -19043.06 respectively, with the same order. In all three solvents, the values of enthalpy and entropy change have been positive and decreased as the donor number of the solvents decreased.

Reaction of a series of zerovalent Fe Lewis bases with Lewis acid GaCl3 leads to both conventional, neutral metal-only Lewis pairs in the case of small metal complexes and cationic gallenium species in the case of larger metal bases. The results suggest the predominance of steric bulk in controlling the outcome of group 13 trihalide Lewis acid additions to metal bases.

The synthesis, structure, and solvatochromism properties of two new complexes with empirical formula [Cu2L2]X2, are described, where HL stands for 2-(N,N-diisopropyl-2-aminoethyl)imino-3-butanone oximato and X is perchlorate or tetraphenylborate anion. The complexes were characterized by elemental analyses, molar conductance and spectral studies. The binuclear complex [Cu2L2](BPh4)2 was analyzed by X-ray crystallography. In complexes the copper centers are bridged through the oximato N O groups forming a dimer containing a crystallographic twofold symmetry axis. The complexes are solvatochromic and their solvatochromism were investigated by visible spectroscopy. The solvent-dependent absorption maxima, λmax, was analyzed using stepwise multiple linear regression (SMLR) method to find the best model explaining the observed positive solvatochromism. The analysis demonstrated that among different solvent parameters, donor number (DN) is a dominant factor responsible for the shift in the d-d absorption band of the complexes to the higher wavelength with increasing its values.

Photocatalytic CO2 reduction using hybrids of carbon nitride (C3N4) and a Ru(II) complex under visible light was studied with respect to reaction solvent. Three different Ru(II) complexes, trans(Cl)-[Ru(X2bpy) (CO)2Cl2] (X2bpy = 2,2'-bipyridine with substituents X in the 4-positions, X = COOH, PO3H2, or CH2PO3H2), were employed as promoters and will be abbreviated as RuC (X = COOH), RuP (X = PO3H2), and RuCP (X = CH2PO3H2). When C3N4 modified with a larger amount of RuCP (7.8 μmol g(-1)) was employed as a photocatalyst in a solvent having a relatively high donor number (e.g., N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)) with the aid of triethanolamine (TEOA) as an electron donor, the hybrid photocatalyst exhibited high performance for CO2 reduction, producing CO and HCOOH with relatively high CO selectivity (40-70%). On the other hand, HCOOH was the major product when RuC/C3N4 or RuP/C3N4 was employed regardless of the loading amount of the Ru(II) complex and the reaction solvent. Results of photocatalytic reactions and UV-visible diffuse reflectance spectroscopy indicated that polymeric Ru species, which were formed in situ from RuCP on C3N4 under irradiation in a solvent having a high donor number, were active catalysts for CO formation. Nonsacrificial CO2 reduction using RuP/C3N4 was accomplished in a DMA solution containing methanol as an electron donor, which means that visible light energy was stored as chemical energy in the form of CO and formaldehyde (ΔG° = +67.6 kJ mol(-1)). This study demonstrated the first successful example of an energy conversion scheme using carbon nitride through photocatalytic CO2 reduction.

Understanding and controlling the kinetics of O2 reduction in the presence of Li(+)-containing aprotic solvents, to either Li(+)-O2(-) by one-electron reduction or Li2 O2 by two-electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li-O2 batteries. Standard potentials of O2 /Li(+)-O2(-) and O2/O2(-) were experimentally measured and computed using a mixed cluster-continuum model of ion solvation. Increasing combined solvation of Li(+) and O2(-) was found to lower the coupling of Li(+)-O2(-) and the difference between O2/Li(+)-O2(-) and O2/O2(-) potentials. The solvation energy of Li(+) trended with donor number (DN), and varied greater than that of O2 (-) ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li(+)-O2(-) solubility and DN. These results highlight the importance of the interplay between ion-solvent and ion-ion interactions for manipulating the energetics of intermediate species produced in aprotic metal-oxygen batteries.

Fluorophosphonium salts C6X4(BR2)Ph2PF[B(C6F5)4] (X = H, F; R = Cy, Mes) exhibit enhanced Lewis acid catalytic reactivity as a results of the proximity of the fluorophosphonium and borane moieties.

The lithium-sulfur (Li-S) battery is one of the promising energy storage alternatives because of its high theoretical capacity and energy density. Factors governing the stability of polysulfide intermediates in Li-S batteries are complex and are strongly affected by the solvent used. Herein, the polysulfide reduction and the bond cleavage reactions are calculated in different solvent environments by the density functional theory (DFT) methods. We investigate the relationship between the donor numbers (DN) as well as the dielectric constants (ε) of the solvent system and the relative stability of different polysulfide intermediates. Our results show that the polysulfide reduction mechanism is dominated by its tendency to form the ion-pair with Li+ in different organic solvents.

The use of concentrated aprotic electrolytes in lithium batteries provides numerous potential applications, including the use of high-voltage cathodes and Li-metal anodes. In this paper, we aim at understanding the effect of salt concentration on the variation of the Li/Li+ Quasi-Reference Electrode (QRE) potential in Tetraglyme (TG)-based electrolytes. Comparing the obtained results to those achieved using Dimethyl sulfoxide DMSO-based electrolytes, we are now able to take a step forward and understand how the effect of solvent coordination and its donor number (DN) is attributed to the Li-QRE potential shift. Using a revised Nernst equation, the alteration of the Li redox potential with salt concentration was determined accurately. It is found that, in TG, the Li-QRE shift follows a different trend than in DMSO owing to the lower DN and expected shorter lifespan of the solvated cation complex., publishedVersion

To fabricate efficient MAPbI3 perovskites using the Lewis acid-base adduct approach, we used a Lewis base hexamethylphosphoramide (HMPA) having a high donor number (DN), and investigated the effect of high-DN HMPA treatment on the properties of planar MAPbI3-based solar cells. The main functions of the HMPA treatment were to passivate the perovskites by forming well-distributed PbI2 phases and to densify the perovskites by controlling the rate constants. The treatment with Lewis base HMPA by one-step spin coating and subsequent solvent washing promoted the formation of pinhole-free perovskite films by increasing the coordination ability of HMPA with Pb2+ adducts and controlling the nucleation and growth rates of the perovskites. In addition, treatment with various concentrations of HMPA led to the formation of a residual PbI2 phase that acted as a passivation layer, even though stoichiometric quantities of precursors were used. Through a series of advanced electron microscopy studies, the exact three-dimensional locations of the PbI2 passivation layers were determined. Furthermore, by calculating the decreased active trap concentrations and carrier densities, we verified the passivation effect of remnant PbI2. Importantly, we achieved the best power conversion efficiency of 17.09% by the controlled addition of Lewis base HMPA, thus demonstrating a much improved performance than that obtained without HMPA treatment (15.73%).

Factors influencing the sign and size of effective surface (zeta) potential in suspensions of very low dielectric constants are evaluated. For non-aqueous suspensions it was found that Gutmann's donor number ( DN = negative Lewis type molar acid-base adduct formation enthalpy) was successfully related to zeta potential changes, similarly as pH is optimal for aqueous suspensions. Negative molar proton dissociation enthalpy (Brϕnsted type HD number), negative hydrogen bond enthalpy ( HB number), logarithmic hydrogen bond equilibrium constant (molar Gibbs free energy), standard reduction potential of solvated protons ( E o ( H L + / H 2 )), electrolytic dissociation potential of water ( E o ( H 2 O / H 2 , O 2 )) and electron exchange Fermi potentials could equally well be related to zeta potential changes. All these properties were linearly dependent on each other. Correlations to products of Gutmann's DN and AN numbers and other relevant properties such as polar, hydrogen bond and acid-base contributions to solubility parameters and to surface tensions were found to be less successful particularly when very polar liquids were encountered. Commonly used DLVO models for repulsive interaction energy between pair of particles in aqueous electrolyte suspensions have been simplified when dealing with low-polar, non-polar and apolar suspensions. When evaluating factors contributing to attractive and repulsive interaction energies, it is found that in order for the models to be relevant the extension of diffuse charging has to be much larger than the distance to repulsive barrier ensuring suspension stability. At this limit and at high surface potentials, the repulsive energy grows exceptionally large being in the range of lattice energy of each solid. The models fail when surface potential is low and the extension of diffuse charging is much smaller than the distance to repulsive barrier. Then interaction energies are reasonable. The investigated (Au, SiO 2 , Glass, TiO 2 , Al 2 O 3 , CaCO 3 , MgO) suspensions fall between these limits. The attractive energy is small but significant as compared to repulsive energy. All energies were larger than the estimated lower limit for stable suspensions.

The sodium oxygen battery is a promising metal-air battery; however, the discharge process is not well understood and the major discharge product is still under debate. The discharge products determined the theoretical specific energy and electrochemical performance of the battery. Now it is demonstrated that NaO2 spontaneously disproportionates to Na2 O2 , no matter whether it is dissolved in solution or stays on the surface. The behaviors of NaO2 in solution and on the surface are different. Solvents play a crucial effect on the disproportionation of dissolved NaO2 species, which is fast in low donor number (DN) solvents such as acetonitrile but sluggish in high DN solvents such as DMSO. In situ XRD results exhibited the different product growing processes in various solvents. Surface NaO2 would slowly disproportionate to Na2 O2 anyway, but this process is relatively slow compared to the time span of discharge process and it does not affect the major product on discharge.

Zinc contaminants have been identified as suspects leading to nozzle deposit formation and copper contaminants quickly reduce the oxidation stability of diesel fuel. Ionic liquids (ILs) are commonly referred to as ‘designer solvents’ due to the great degree of fine-tuning of physical and chemical properties afforded by modification of the constituent cation and anion. The tunable properties of the IL ions allows the ‘design’ to meet the requirements for a particular application, making ILs an ideal potential candidate for the extraction of trace (ppb to ppm) amounts of zinc and copper heavy metals from diesel fuel. We report for the first time that ILs can extract up to 99.3% of zinc at a zinc concentration of just 2 mg kg−1 and copper can be extracted up to 99.7% at copper concentration of just 1 mg kg−1 from a model diesel fuel. Factors affecting the extent of extraction were investigated via correlation with experimental descriptors. 23Na NMR was used in the determination of donor number (DN) and Kamlet–Taft parameters were gathered for each IL providing information of possible hydrogen-bond acidity/basicity (α/β), and dipolarity/polarizability effects (π*). In addition, the non-random two liquid (NRTL) model was applied to determine τ parameters for each of the ILs. We determined that the extraction is controlled strongly by the hydrogen bond basicity of the IL which is directly related to the ability of the anion of the IL to complex Zn2+ and Cu2+ thus removing it from the fuel. DN, τ parameters and β, in addition to density and viscosity values, provide further information on the extraction mechanisms and predict performance, informing chemical design of ILs that are ideal for fuel purification.

Trace amounts of dissolved sodium has been identified as one possible cause leading to the formation of internal diesel injector deposits (IDIDs) which prove problematic by reducing fuel efficiency in high pressure diesel injectors. We demonstrate the successful extraction of ppm levels of Na+ from a model diesel fuel. A range of ionic liquids (ILs) with a variety of cations and anions were examined for their effectiveness at different loadings of IL relative to the model diesel fuel. Results provide several clear trends with some exceptional capabilities of the ILs in the extractions. ILs are commonly referred to as ‘designer solvents’, due to the great degree of fine-tuning of physical and chemical properties afforded by modification of the constituent cation and anion. The tunable properties of the ILs ions allow the ‘design’ to meet the requirements for a particular target and here provide several potential candidates for the extraction of the ppm levels of sodium from diesel fuel. We report for the first time that ILs can extract up to 99.1% of Na+ from a model diesel fuel at a Na+ concentration of just 3 mg kg−1 in the fuel; factors affecting the extent of extraction were investigated via correlation with experimental solvent descriptors. 23Na NMR was used in the determination of donor number (DN), and Kamlet–Taft parameters were gathered for each IL providing information of possible hydrogen-bond acidity/basicity (α/β) and dipolarity/polarizability solvent strength (π*). In addition, the non-random two liquid model (NRTL) was applied to correlate the experimental extraction results and determine τ parameters for each of the ILs. We determined that the extraction is controlled strongly by the Lewis basicity of the IL which is directly related to the ability of the anion of the IL to complex Na+ and thereby remove it from the fuel. DN, τ parameters and β, in addition to interfacial tension and viscosity values, provide further information on the extraction mechanisms and predict performance, enabling chemical design of ILs that are ideal for fuel purification.

Solvatochromic nickel(II) complexes with diketonato and diamine ligands were incorporated into a saponite clay by ion exchange, and their colorimetric humidity- and solvent-recognition properties were investigated. These powders exhibit color change from red to blue-green depending on humidity, and the detection range can be controlled by modifying the metal complex. The humidity response takes advantage of the humidity-dependent water content in clay and the coordination of water molecules to the metal complex in equilibrium. The addition of organic solvents to the powders causes a color change to occur, varying from red to blue-green depending on the donor number of the solvent, thereby enabling solvent recognition. In the clay, the affinity of less sterically hindered complexes to water or solvent molecules is decreased compared with that in solution because the cationic complexes interact with the anionic layers in the clay. Incorporating diethylene glycol into the materials produced thermochromic powders.

A number of zerovalent ruthenium tri- and tetracarbonyl complexes of the form [Ru(CO)5-n Ln] (n=1, 2) with neutral phosphine or N-heterocyclic carbene donor ligands have been treated with the Lewis acids GaCl3 and Ag(+) to form a range of metal-only Lewis pairs (MOLPs). The spectroscopic and structural parameters of the adducts are compared to each other and to related iron carbonyl based MOLPs. The Lewis basicity of the original Ru(0) complexes is gauged by transfer experiments, as well as through the degree of pyramidization of the bound GaCl3 units and the Ru-M bond lengths. The work shows the benefits of the MOLP concept as one of the few direct experimental gauges of metal basicity, and one that can allow comparisons between metal complexes with different metal centers and ligand sets.

The paper presents a combined experimental and computational study on a mixed chelate copper(II) complex containing the bidentate ligands N,N-diethyl,N′-benzyl-1,2-diaminoethane (diamEt) and 1-phenyl-1,3-butanedione (Ph-acac). The complex [Cu(Ph-acac)(diamEt)]ClO4 was characterized by elemental analysis, IR, molar conductivity measurements and single crystal X-ray analysis. The square pyramidal geometry of the complex made it a good solvatochromic probe with the color change range from purple to green in 14 organic solvents. The observed solvatochromism was analyzed by statistical method. The obtained results revealed that the donor number (DN) parameter of the solvent plays a dominate contribution to the observed positive solvatochromism. The cationic structure of the complex was optimized by DFT methods. Infrared spectral analysis of the compound was carried out by theoretical calculation and compared with the experimental spectrum to assign the vibrational transitions. The solvatochromic behavior of the complex was also explored by TD-DFT method in different solvents. The calculated visible absorption spectra of the complex were in harmony with the experimental ones.

The protonation constants of the syn ketoxime, 2-(hydroxyimino)-1-(2-hydroxyphenyl)butane-1,3-dione (HPDO) were determined by a pH-metric method in solutions of dioxane, methanol and dimethylformamide (75 % v/v) at 20 ± 0.1 °C and ionic strength of 0.1 mol·L−1 supported by KNO3. The complexation reaction of the ligand HPDO with the transition metal ions Cu(II), Ni(II), Co(II), Cr(III), Fe(III), and Mn(II) in solution has been also studied potentiometrically. The stability constants of the respective species were determined and show that their values decrease in the order: 1,4-dioxane

A series of boronate-π-acceptor compounds containing different types of π bridges (1,4-phenylen or thien-2,5-diyl or furan-2,5-diyl) that link the switchable boronate ester group with the efficient TCF acceptor group (TCF=2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran) has been synthesized. A TCF chromophore of this type undergoes transition to a donor-π-acceptor compound upon coordination of Lewis bases at the Lewis acidic boron center, which is accompanied by an enhanced intramolecular charge-transfer interaction. The Lewis acid character has been investigated by spectroscopic measurements (UV/Vis, NMR spectroscopies) as well as DFT and ab initio-based calculations. It is shown that the TCF acceptor group and thiophene or furan π-bridges directly bound to the boron atom cooperatively increase the Lewis acidity. UV/Vis titration experiments confirm fluoride binding constants in the range of up to 10(8) M(-1) in CH2 Cl2 . In addition to the strong boron fluoride binding motif, Lewis interactions also occur with weaker Lewis bases, such as pyridine or aliphatic alcohols. The unique combination of chromophoric and Lewis acidic properties is responsible for the intense colorimetric turn-on response detectable after complex formation.

This paper investigates the effect of a small amount of a strong electron-donating solvent (or high electron donor number solvent) on the solvent swelling of covalently and non-covalently cross-linked Kukersite oil shale kerogen in non-polar solvents. The non-polar (or non-specifically interacting) solvents used in the study were benzene, o-xylene and tetralin. The specifically interacting (or swelling promoting), high donor number solvent added was N-methyl-2-pyrrolidinone (NMP). The changes in solvent uptake of the samples caused by the specifically interacting solvent, previously in equilibrium with respect to a non-specifically interacting solvent, were studied using a Differential Scanning Calorimeter (DSC). The specifically interacting solvent was added in small amounts, up to roughly 2 mmol of NMP per gram of kerogen (that is, 0.208, 0.416, 0.624, 0.831, 1.039 and 2.07 mmol of NMP per gram of kerogen). The experiments indicated an increase up to about two times in the swelling ratio by adding a strong electron donor solvent at 0.8 mmol per gram of kerogen. The effect was most pronounced in the case of tetralin, the solvent with the lowest initial swelling ratio and the largest molar volume. From solvent melting point depression and gas chromatography (GC) experiments, it could be stated that up to 0.8 mmolNMP/gkerogen most of the high electron donor solvent was absorbed by the Kukersite kerogen. The value 0.8 mmol NMP per gram of kerogen is specific to Kukersite oil shale kerogen. The DSC-based method applied can be considered quantitative up to this limiting value of 0.8 mmol NMP per gram of kerogen, and above this value the results indicate characteristic trends.

The spectral dynamics of a series of rhenium photocatalysts, fac-Re(4,4'-R2-bpy)(CO)3Cl, where R = H, methyl, t-butyl, and carboxylic acid, as well as Re(1,10-phenanthroline)(CO)3Cl were observed in multiple aprotic solvents using two-dimensional infrared spectroscopy (2DIR). The carbonyl vibrational stretching frequencies showed slight variations due to the electron-donating or -withdrawing nature of the substituents on the bipyridine. The different substituents had minimal to no influence on the spectral diffusion time scales of the compounds within a particular solvent, but among the three different solvents investigated (DMSO, THF, and CH3CN), we find the spectral diffusion times to correlate with the solvent's donor number (DN). Because the donicity is a measure the Lewis basicity of the solvent, these findings may help establish a more complete dynamical picture of the photocatalysis, where the first chemical step following optical excitation is electron transfer from a sacrificial donor to the rhenium complex.

Equilibria for the reactions of benzhydryl cations (Ar2CH(+)) with phosphines, tert-amines, pyridines, and related Lewis bases were determined photometrically in CH2Cl2 and CH3CN solution at 20 °C. The measured equilibrium constants can be expressed by the sum of two parameters, defined as the Lewis Acidity (LA) of the benzhydrylium ions and the Lewis basicity (LB) of the phosphines, pyridines, etc. Least-squares minimization of log K = LA + LB with the definition LA = 0 for (4-MeOC6H4)2CH(+) gave a Lewis acidity scale for 18 benzhydrylium ions covering 18 orders of magnitude in CH2Cl2 as well as Lewis basicities (with respect to C-centered Lewis acids) for 56 bases. The Lewis acidities correlated linearly with the quantum chemically calculated (B3LYP/6-311++G(3df,2pd)//B3LYP/6-31G(d,p) level) methyl anion affinities of the corresponding benzhydrylium ions, which can be used as reference compounds for characterizing a wide variety of Lewis bases. The equilibrium measurements were complemented by isothermal titration calorimetry studies. Rates of SN1 solvolyses of benzhydryl chlorides, bromides, and tosylates derived from E(13-33)(+), i.e., from highly reactive carbocations, correlate excellently with the corresponding Lewis acidities and the quantum chemically calculated methyl anion affinities. This correlation does not hold for solvolyses of derivatives of the better stabilized amino-substituted benzhydrylium ions E(1-12)(+). In contrast, the correlation between electrophilic reactivities and Lewis acidities (or methyl anion affinities) is linear for all donor-substituted benzhydrylium ions E(1-21)(+), while the acceptor-substituted benzhydrylium ions E(26-33)(+) react more slowly than expected from their thermodynamic stabilities. The boundaries of linear rate-equilibrium relationships were thus defined.

The aim of present study is to establish the not known divalent state of praseodymium and samarium in non-aqueous medium at 298.15 K and atmospheric pressure. Potentiostatic and galvanostatic methods were used to characterize the divalent states of both lanthanides. Under the specified experimental conditions, samarium and praseodymium showed two reduction steps at glassy carbon electrode in non-aqueous medium. Cathodic and corresponding anodic peak potential and peak currents were calculated for samarium and praseodymium ions at different scan rates. The results also suggest that the scan rate has great influence on the behaviour of both lanthanides. Diffusion coefficient (D × cm 2 sec -1 ) and heterogeneous forward rate constant (ko fh × cm sec -1 ) have been evaluated. Transition time ( τ) has also been evaluated for Pr(III)/Pr(II), Pr(II)/Pr(0) coupled systems, suggesting that the system is approaching from irreversible with increasing the scan rates. The effects of changing the scan rate and donor number on the electrochemical behavior of both lanthanides have been examined at 298.15 K and atmospheric pressure.

A series of Donor-Acceptor-Donor (D-A-D) and Acceptor-Donor-Acceptor (A-D-A) compounds have been prepared exploiting the relative ability of polyfluorinated azobenzenes and benzophenone to undergo aromatic nucleophilic substitution reactions with aromatic amines. A high para-regioselectivity is obtained when fluorene and carbazole-based diamines have been used in a high Donor Number solvent environment such as DMSO. The prepared triads have been employed in the synthesis of oligomers with the aim of evaluating them as photovoltaic material additives in optoelectronic applications.

Prins condensation of β-pinene with paraformaldehyde was carried out over MoOx/γ-Al2O3 catalyst in liquid phase. MoOx/γ-Al2O3 catalysts with different loadings were synthesized by impregnation method and characterized by XRD, N2 sorption, NH3-TPD, UV-DRS, TEM and SEM. The surface area, TEM and UV-DRS measurements reveal complete coverage of alumina support by MoOx was achieved between 9 and 11 wt% loading in which the molybdenum is present as octahedral and tetrahedral species in the form of a monolayer domain and small clusters of MoOx. The effect of MoOx loading and calcination temperature of the catalysts on total acidity and catalytic activity in the Prins reaction were correlated. The total surface acid density of MoOx/γ-Al2O3 increased with an increase in MoOx loading until 11 wt% and further loading decreased the acidity. Among the different supports, ZrO2, TiO2, SiO2 and Nb2O5, γ-Al2O3 exhibited the best performance. The influence of solvent on the Prins reaction in terms of dielectric constant, acceptor and donor number was investigated. Solvents with both AN and DN in the range of 10 to 20 were suitable to facilitate the reaction. The effect of reaction temperature, catalyst amount, reactant mole ratio and reusability of the catalyst for the Prins reaction were investigated. The 11 wt% MoOx loaded on γ-Al2O3 showed the best performance with 96% β-pinene conversion with 86% nopol selectivity.

We report on the detection of metastable, solvated, and surface adsorbed alkali metal–oxygen (M–O2) discharge species using in situ attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). Oxygen–oxygen stretching bands (νO–O) of superoxide species formed during M–O2 battery discharge have been challenging to observe by conventional infrared (IR) techniques, and because of this, there has been limited use of IR techniques for in situ monitoring of the discharge products at the cathode in metal–O2 batteries. We explore SEIRAS technique to investigate lithium–oxygen and sodium–oxygen electrochemistry in acetonitrile (MeCN; a low Gutmann donor number solvent) as well as dimethyl sulfoxide (DMSO; a high Gutmann donor number solvent) in order to demonstrate the feasibility of our approach in the ongoing efforts toward the realization of M–O2 battery technology. In situ IR spectroscopy studies, together with a coupled-cluster method including perturbative triple excitations [...

The molecular life of intermediates, namely, O2- and Li+ , produced during the discharge of aprotic Li-O2 batteries was investigated by molecular dynamics simulation. This work is of potential interest in the development of new electrolytes for Li-air batteries. We present the results on the structure and stability of the Li+ and O2- solvation shells and the thermodynamics and kinetics of the ion-association reaction in solvents such as dimethyl sulfoxide (DMSO), dimethoxyethane (DME), and acetonitrile (ACN). The residence time of solvent molecules in the Li+ solvation shell increases with the solvent donor number and is 100 times larger in DMSO than in ACN. In DMSO and DME, the Li+ ion diffuses with its solvation shell as a whole. On the contrary, in ACN it diffuses as a "bare" ion because of weak solvation. The rate constant for the association of the lithium ion with the superoxide anion in DMSO is two orders of magnitude slower than that in ACN due to fact that the free-energy barrier is 2.5 times larger in DMSO than in ACN. In addition, we show that despite the strong dependence of the Li+ shell stability on donor number, the rate of association does not necessarily correlate with this solvent property.

Proton transfer promoted by the coordination of protogenic Lewis bases to a Lewis acid is a critical step in catalytic transformations. Although the acidification of water upon coordination to a Lewis acid has been known for decades, no attempts have been made to correlate the Bronsted acidity of the coordinated water molecule with Lewis acid strength. To probe this effect, the pKa's (estimated error of 1.3 pKa units) in acetonitrile of ten protogenic Lewis bases coordinated to seven Lewis acids containing Lewis acidities varying 70 kcal mol−1, were computed. To quantify Lewis acid strength, the ability to transfer a hydride (hydride donor ability) from the respective main group hydride was used. Coordination of a Lewis acid to water increased the acidity of the bound water molecule between 20 and 50 pKa units. A linear correlation exhibiting a 2.6 pKa unit change of the Lewis acid–water adduct per ten kcal mol−1 change in hydride donor ability of the respective main group hydride was obtained. For the ten protogenic Lewis bases studied, the coordinated protogenic Lewis bases were acidified between 10 and 50 pKa units. On average, a ten kcal mol−1 change in hydride donor ability of the respective main group hydride resulted in about a 2.8 pKa unit change in the Bronsted acidity of the Lewis acid–Lewis base adducts. Since attempts to computationally investigate the pKa of main group dihydrogen complexes were unsuccessful, experimental determination of the first reported pKa of a main group dihydrogen complex is described. The pKa of H2-B(C6F5)3 was determined to be 5.8 ± 0.2 in acetonitrile.

Our interest in the functionalization of [sbnd]OH-substituted azaborines prompted us to synthesize a 1-hydroxy-2,3,1-benzodiazaborine conjugated with 1,8-naphthalimide 1. Its fluorescence was dramatically affected by the nature of the solvent. In particular, the use of DMSO, which has a relatively high donor number (DN = 29.8), led to a remarkable decrease in the fluorescence intensity (ΦF = 0.0014), possibly due to intermolecular hydrogen-bonding interactions (Me2S[dbnd]O⋯HO[sbnd]B). The presence of the hydroxyl group on boron led to a solvent-driven colorimetric response towards anions; high selectivity for F− over other anions in DMSO, and responded to AcO− and F− in THF, as shown by UV/vis titrations, NMR, and mass spectroscopic analysis. The nucleus-independent chemical shift (NICS) indices suggested that hydrogen bonding interactions between Me2S[dbnd]O and HO[sbnd]B reduced the aromaticity of the benzodiazaborine macrocycle, causing an increase in the negative character of the boron. The increase in the polarity of the B[sbnd]N bond may prevent acetate-binding of 1 in DMSO.

The enhancement of donor strength of ortho—functionalized triarylphosphanes is shown to occur via different mechanisms for O- and N- donor substituents, with internal solvation of the phosphorus center observed for N—- donors. Nevertheless, the steric congestion about the P— center is shown to significantly oppose the increase in donor ability, leading to donation weaker than that expected. A series of mono- and bis-aryl -substituted Ar3PI2 adducts—[(Ph3—-?n (o-OMe-C6H4) n PI2, Ph3—-?n (o-NMe2-C6H4) n PI2, Ph3—-?n (o-CH2NMe2-C6H4) n PI2 (n =—1——,21, 2—)]) have been synthesized via the 1:1 reaction of donor-functionalized phosphanes with diiodine. These soft Lewis acid/base adducts exhibit apparent internal solvation of the donor phosphorus by the pendant donor moieties, giving rise to five- or six-coordinate phosphorus atoms acting as both Lewis base and Lewis acid; the first neutral six-coordinate simultaneous P(III) Lewis acid and Lewis base adduct is reported. Single -crystal X-ray diffraction studies reveal unexpectedly weak donor strength for one of the phosphanes, indicating significant steric hindrance as a consequence of internal solvation. Crystallographic interrogation of the corresponding iodophosphonium salts [Ar3PI]X (X = I3, BArF) shows that the cationic complexes experience a still greater influence of the steric bulk of the donor moieties than their neutral precursors. The steric and electronic contributions to bonding have been analyzed through computational studies, determining the factors governing the basicity of these donor—functionalized phosphanes, and show that enhancement of P-centered donor strength occurs by conjugation of lone pairs through the arene rings for oxygen substituents, and via internal solvation for the nitrogen donors.

The absorption and fluorescence spectroscopy measurements of three derivatives of pyrazolequinoline chemosensor in protonated environment were examined. The absorption spectroscopy measurements have shown high probability of complexation. Fluorescence quenching of pyrazolequinoline in solution with addition of acidic acid and/or trifluoroacetic acid was observed and the Stern–Volmer quenching constants were calculated: 153, 368 and 89 [L mol−1]. Semi-empirical calculations and optimization of molecular structure of the pyrazolequinoline in vacuum, in water and in a proton-rich environment were performed using Gaussian 09 software package. These studies have shown high probability of intermolecular hydrogen bonds that were formed by the protons with nitrogen atoms being potentially able to interact. The formation of pyrazolequinoline-acid complexes confirm the possibility of proton transfer process. These studies shown that the proton transfer mechanism is strongly dependent on environment properties like solvent parameters: Donor Number and Acceptor Number. The selective interaction of the proton with the molecule seems to be strong.

To develop solvent-recognition films, Nafion membranes incorporating cationic nickel-chelate complexes, that is, [Ni(L(1))(L(2))](+) (HL(1) = acetylacetone, 2,2,6,6-tetramethyl-3,5-heptanedione; L(2) = N,N-diethylethylenediamine, N-butyl-N,N',N'-trimethylethylenediamine), were prepared. Immersion of the films in various solvents effected the color changes varying from red to pale blue green depending on the donor number of the solvents. The color change is based on an equilibrium shift between square-planar and solvent-coordinated octahedral geometries of the cations. The degree of the color change depended on the affinity of the incorporated complex to the solvent molecules. The films were robust and exhibited a reversible solvent response. The films exhibited thermochromism when a small amount of appropriate solvents were incorporated and changed from pale blue green at low temperatures to red at high temperatures.