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The study conducted led to the following conclusions: — Ionic liquids based on the 1-butyl-3methylimidazolium cation are not solvents for most synthetic polymers, but dissolve natural polymers characterized by a large number of H bonds in the supramolecular structure up to high concentrations. — The dissolving power of IL based on the 1-butyl-3-methylimidazolium cation is a function of the nature of the anion and the value of the negative charge on its electron-donor sites: IL with an acetate anion dissolve natural polymers better than liquids with a chloride anion. — An increase in the length and number of hydrophobic alkyl radicals in the imidazolium cation increases the hydrophoby of the IL and is accompanied by a decrease in the dissolving power with respect to natural polymers. The charge distribution in the imidazolium cation is a function of the length and number of alkyl radicals, determines the strength of the cation—anion bond, and the dissolving power of the IL changes proportionally to this strength. — Incorporation of proton-donor diluents decreases the dipole moment and value of the negative charge of the IL anion, which results in loss of the dissolving power of the binary mixture. — Aprotic diluents can be incorporated in these IL, and the change in the dissolving power of the binary mixture will be a function of the donor capacity of the aprotic diluent: a smaller decrease in the dissolving power is observed for the binary mixture in which the diluent has a lower donor number and more weakly competes with the IL for formation of hydrogen bonds with the polymer.

Condensation of 3-[(diphenylphosphanyl)methyl]benzene-1,2-diol (1) with phenyl boronic acid gave a phosphane-functionalised benzo-1,3,2-dioxaborol 3. The ability of this species to act as a Lewis base through the P-centered donor and as a Lewis acid through the B-centered acceptor sites was demonstrated by the reactions with (cod)PdCl2 and some nitrogen donors (4-dimethylaminopyridine, diaza-[2.2.2]-bicyclooctane, pyridine). These reactions yielded either palladium–phosphane complexes or amine–borane adducts that were characterised by spectroscopic data and, in some cases, by single-crystal X-ray diffraction studies. Reactions of a Pd complex of the phosphane-functionalised benzo-1,3,2-dioxaborol 3 with dabco, or of the dmap adduct of 3 with (cod)PdCl2, gave materials that were characterised by analytical data and solid-state NMR spectroscopic data as triple Lewis acid/base complexes and that contain both PPd and BN dative bonds. Even though these adducts were unstable in solution, the results of these experiments demonstrate the ability of 3 to act as a bifunctional donor/acceptor ligand, which is of potential use as a building block for main chain organometallic polymers or multimetallic complexes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The complexation reaction between Zn 2+ , Pb 2+ , Cd 2+ and T 1+ cations by 5,7-diiodo-8-hydroxyquinoline (IQN) was studied in the Dimethylformamide /Acetonitril (DMF-AN) binary system using square wave polarography technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-wave or peak potential of the polarographic waves of metal ions against the ligand concentration. The stoichiometry of the complexes was found to be 1:1. The results obtained show that there is an inverse relationship between the formation constant of the complexes and the donor number of solvent base on the Guttmann donocity scale. In all cases the formation constants increased with increasing amounts of AN in these binary systems. The selectivity order for IQN complexes with the cations is Zn 2+ > Pb 2+ > Cd 2+ > T1 + .

The effect of solvent participation on the ligand-to-metal charge transfer (LMCT, L → CoIII) reduction of the of CoIII(en)2Br(RC6H4NH2)2+ where R = m-OCH3, p-F, H, m-CH3, p-CH3, p-OC2H5 and p-OCH3 were examined in aqueous 2-methyl-2-propanol (ButOH) solutions. The change in the reduction behavior of CoIII centre was also examined through cyclic voltammetric studies. The observed reduction in quantum yield due to LMCT excitation can mainly be accounted using linear solvation energy relationship (LSER) comprising model correlation equations. These consist of empirical parameters such as Grunwald–Winstein's solvent ionizing power, Y, Dimroth–Richardt's solvent micro-polarity parameter, E T N , Gutmann's donor number, DNN, along with Kamlet–Taft's solvatochromic parameters (hydrogen bond acceptor acidity/basicity α/β and solvent dipolarity/polarizability, π*). The origin of solvent effect is found to be due to microscopic interaction between the solvent donor and the nitrogen-bound hydrogen of the ligand. Cyclic voltammograms show an irreversible reduction of CoIII in DMF using Glassy Carbon Electrode, GCE, the redox peaks for the aniline complexes appear at −0.20 and 0.525 V. Irradiation of the complexes with UV light (λ = 254 nm) in binary mixtures produce CoIIaq and the concentration of this species are highly dependent on xalc (xalc = mole fraction of alcohol). The observed quantum yield (log ΦCo(II)) is found to be linearly related to mole fraction of organic co-solvent added in the mixture, therefore, log ΦCo(II) = 26.41 × 10−2 when x2 = 0.0094 and 43.75 × 10−2 when x2 = 0.076 for a typical complex CoIII(en)2Br(p-OCH3C6H4NH2)2+ in aqueous 2-methyl-2-propanol at 300 K. Cyclic voltammetry and LSER analyses illustrate the variation of reduction property of Co(III) by the aryl ligand and homogeneous solvation of the excited state of the complex CoIII(en)2Br(RC6H4NH2)2+ in H2O/ButOH mixtures.

Formation of Cu(II) complexes of 1‐alkyl‐2‐ethylimidazoles (where alkyl=propyl, butyl, pentyl, hexyl, and octyl) has been studied by using the liquid‐liquid partition method, at 25°C and a fixed ionic strength of the aqueous phase (I=0.5; (HL)NO3, KNO3). The complexes were extracted with 2‐pentanone, 2‐butanol, isoamyl alcohol, 2‐ethyl‐1‐hexanol, dichloromethane, trichloromethane, and toluene. The length of the 1‐alkyl group and the nature of solvent have been shown to influence the extraction process. Extraction curves (log DM vs. pH) are displaced towards lower pH's with increasing chain length of the 1‐alkyl substituent and donor number of the solvents. Stability constants of the complexes in aqueous solution were determined as well as their partition ratios between the aqueous and organic phase. The stability of the Cu(II) complexes increased with increasing 1‐alkyl chain length. The stability constants are comparable with βn ones for the Cu(II) complexes of 1‐alkyl‐2‐methylimidazoles, but sm...

The crystal structure of a mineral may be divided into two parts: (1) the structural unit, an array of high-bond-valence polyhedra that is usually anionic in character, and (2) the interstitial complex, an array of large low-valence cations, simple anions and (H2O) groups that is usually cationic in character. Interstitial complexes link the structural units with weak cation-anion and hydrogen bonds into a continuous structure, and the breakdown of a structure is usually controlled by the strengths of the weak bonds that link the structural units together. The interstitial complex is (usually) a complex cation, and can be characterized by its Lewis acidity, a measure of the electrophilic character of the complex. The structural unit is (usually) a complex oxyanion, and can be characterized by its Lewis basicity. The interaction between the structural unit and the interstitial complex can be examined using the principle of correspondence of Lewis acidity-basicity. If one examines a series of structures with the same structural unit, it is evident that the average coordination of the O atoms of the structural unit varies slightly from one structure to another, producing a range of Lewis basicity for this specific structural unit. In this way, a specific structural unit can be stable over a range of Lewis basicity (i.e., over a specific pH range). The formula of an interstitial complex may be written in the following way: {[m] M + a [n] M 2+ b · [l] M 3+ c(H2O)d(H2O)e(OH)f(H2O)g}(a+2b+3c–f)+, where [m], [n] and [l] are coordination numbers, a, b and c are the numbers of monovalent, divalent and trivalent cations, d is the number of transformer (H2O) groups, e is the number of (H2O) groups bonded to two interstitial cations or one interstitial cation and one hydrogen bond, f is the number of interstitial (OH) groups, and g is the number of (H2O) groups not bonded to any cation. The number of transformer (H2O) groups strongly affects the Lewis acidity of the interstitial complex, and the variation in Lewis acidity of a generalized interstitial complex can be graphically represented as a function of the number of transformer (H2O) groups. Where the Lewis acidity of a generalized interstitial complex overlaps the range of Lewis basicity of a specific structural unit, the principle of correspondence of Lewis acidity-basicity is satisfied and a stable structural arrangement is possible. Detailed predictions of the compositions of interstitial complexes are made for the borate, sulfate and uranyl-oxide-hydroxy-hydrate minerals. There is fairly close agreement between the predicted ranges of interstitial complex and those observed in Nature.

The electric double layer structure is studied on a dropping liquid Cd-Ga electrode (0.3 at % Cd) in a solvent with a high donor number (DN), namely, in hexamethylphosphorotriamide (HMPTA, DN = 38.8). A very strong chemisorption interaction of this electrode with HMPTA molecules is registered. The chemisorption potential drop in HMPTA on Cd-Ga electrode is found to be comparable with similar values observed earlier in various solvents on catalytically active metals of platinum subgroup. The data obtained on the Cd-Ga electrode are compared with the corresponding data on Hg, Ga, and In-Ga electrodes. It is shown that the chemisorption interaction energy of studied electrodes in HMPTA grows in the following series: Hg < In-Ga < Cd-Ga < Ga. The same as on In-Ga and Ga electrodes, the chemisorption potential drop on the Cd-Ga electrode increases in a series of solvents with the increase in the solvent DN. Hence, this dependence has a general character. The whole set of obtained results confirms the concept of the donor-acceptor nature of the metal-solvent specific interaction at which the solvent molecules chemisorbed at the electrode surface donate an electron pair to the metal.

The charge distribution on isolated polar molecules has been determined in the gas phase on the basis of the natural bond order (NBO) analysis. It is shown that the fractional negative charge on the heteroatom or atoms associated with solvent basicity is linearly correlated to popular empirical measures of this parameter in the liquid phase, namely, the solvent’s donor number, DN, and its solvatochromic basicity B SC.

The effect of solvents in liquid electrolyte on the photovoltaic performance of dye-sensitized solar cells was investigated. The solvents with large donor number enhanced the open-circuit voltage but reduced the short-circuit current density. By mixing 30 vol.% NMP with 70 vol.% GBL, the open-circuit voltage increased from 0.55 to 0.632 V and the fill factor increased from 0.607 to 0.613 while the short-circuit current density decreased little. The further addition of 0.4 M pyridine into the above mixed solvent caused a huge increase of overall conversion efficiency from 5.73 to 6.70% under irradiation of 100 mW cm−2.

The spectroscopy and photophysics of trans-[Cr(cyclam)(NCS)2]+ (where cyclam is 1,4,8,11-tetraazacyclotetradecane) were studied in a range of solvents. The cyclam NH stretching vibration [nu(NH)] wavenumber correlates with the Gutmann donor number, whereas the thiocyanate CN stretching vibration [nu(CN)] wavenumber correlates with the Snyder solvent strength (P') scale. These results signify that there is a difference in the solvent interactions with the two types of ligands. The energy of the ligand-to-metal charge transfer absorption maximum between 310 and 320 nm and the energy of the spin-forbidden (doublet-quartet) absorption and emission bands above 700 nm correlate with the nu(CN) wavenumber. This establishes the dominant role of solvent effects at the NCS- ligand in "tuning" the energy of these spectroscopic features. Quantum yields phirx for photosubstitution are0.02 at 54 degrees C and0.002 at 22 degrees C, demonstrating that photochemical reaction is a very minor pathway. The effects of solvent and temperature on the nonradiative decay of the doublet excited-state were investigated by observing the time-resolved phosphorescence between 700 and 750 nm. Below 30 degrees C, the lifetimes are relatively temperature-independent, whereas at higher temperatures, a strong Arrhenius-type dependence is observed. Values for the preexponential factor (A) and the activation energy (Ea) are solvent-dependent and follow a Barclay-Butler-type correlation. These observations are consistent with a dominant back-intersystem crossing pathway for nonradiative decay in the higher-temperature region. From trends observed between ln(A) and the nu(CN) frequency, it appears that solvent effects at the thiocyanate ligand play a dominant role in influencing the rate of nonradiative decay in the high-temperature region.

The novel $$[\hbox{M(acs)}_{2}($$ 3- $$\hbox{pic})_{2}(\hbox{H}_{2}\hbox{O})_{2}]$$ [M: MnII, CoII, and NiII] and $$[\hbox{Cu(acs)}_{2}($$ 3- $$\hbox{pic)}_{2}]$$ complexes (acs: acesulfamate; 3-pic: 3-methylpyridine) have been synthesized and characterized using elemental analyses, magnetic moments, UV–Vis and FT-IR spectra. The thermal behaviour of the complexes was also studied by simultaneous TG, DTG and DTA methods in static air atmosphere. The chromotropic properties of all complexes have been studied using thermal and spectral analysis. While the complexes of CoII and NiII show reversible continuous thermochromism, an irreversible discontinuous thermochromism is observed in the MnII and CuII) complexes in the solid state. The observed thermochromism in the MnII, CoII and NiII complexes is due to the different ligand field strength associated with the deaquation reaction. The solvatochromic behaviour of the complexes is also studied and all $$[\hbox{M(acs)}_{2}(3 \hbox{-pic})_{2}]$$ anhydrous complexes (except MnII) exhibit solvatochromic properties depending on the donor number of the solvent.

Adsorption of various classes of organic compounds has been studied on silicas chemically modified by silanes that contain a trimethylsilyl group: (CH3)3Sil(TMS) and (CH3)3Si(CH2)3(CH3)2SiCl (C3TMS). The effect caused by the nature of the adsorbate and grafted groups on the thermodynamic parameters of adsorption has been studied. Surface modifying is shown to dramatically decrease the Henry constants of n-alkane adsorption equilibrium relative to the unmodified matrix. The contribution of specific interactions to adsorption, estimated by different methods, in the TMS-silica sample is higher than in the C3TMS-silica sample.

We have examined general rules for the change of frequency of stretching vibrations of UO22+ (uranyl) as a function of U-O and uranium-ligand interatomic distances. We analyzed the behavior of these frequencies as a function of donor number (DN) of the organic ligand by studying IR absorption and visible luminescence spectra. A linear correlation was found. We proposed spectroscopic methods for determining the DN of ligands, which are difficult to estimate by other methods, and the composition and structure of uranium complexes.

In the present work the oxidation of ferrocene, Fe(C5H5)2, to the ferrocenium cation, Fe(C2H5)2 +, was examined in the solvents acetonitrile (ACN), acetone (ACE), N-methylformamide (NMF), N,N-dimethylformamide (DMF), N,N-dimethylacetanide (DMA), 3-pentanone (PEN), dimethyl sulfoxide (DMSO) and dichloromethane (DCM) over the temperature range from 248.15 to 298.15 K using the technique of cyclic voltammetry. The anodic (E pa) and the cathodic (E pc) peak potentials, as well as the corresponding anodic (i pa) and cathodic (i pc) peak currents, were obtained at different scan rates (0.02, 0.05, 0.08 and 0.10 V ·s–1). The half-wave potentials (E 1/2) of the Fe(C2H5)2 +/Fe(C5H5)2 couple in the investigated solvent media have been evaluated. The diffusion coefficients (D) have been calculated using the Randles-Sevcik equation. The effects of changing the scan rate, the temperature and properties of the solvent medium such as viscosity and donor number on the electrochemical behavior of ferrocene have been examined.

We have examined the solute–solvent interactions by measuring Raman spectra of CO2 in neat supercritical CO2 (sc-CO2), and sc-CO2 containing β-diketones (acetylacetone, trifluoroacetylacetone, and hexafluoroacetylacetone) and uranyl β-diketonato complex [UO2(hfacac)2DMSO] (hfacac: hexafluoroacetylacetone, DMSO: dimethyl sulfoxide). As a result, it was found that the Raman bands of sc-CO2 containing β-diketones are shifted to lower wavenumber compared with those of neat sc-CO2 and that such a red-shift is not observed in sc-CO2 containing UO2(hfacac)2DMSO. From these results, it was suggested that the Lewis acid–Lewis base (LA–LB) interactions between carbonyl oxygens of β-diketones and CO2 carbon, and the hydrogen bondings between OH of β-diketones and CO2 oxygen are formed in sc-CO2 containing β-diketones, and that the shifts in Raman bonds of sc-CO2 can be used as the measure of CO2-philicity of solutes in sc-CO2. On the basis of such results, we measured Raman spectra of CO2 in sc-CO2 containing compounds with different donicity. As a result, we found out that the wavenumbers (νl) of Raman bands of CO2 correlate with the donor number (DN) of compounds, i.e., νl = 1281.24–0.0109 DN at 25.0 MPa and 40 °C.

Counterion- and solvent-specific swelling behaviors were investigated for alkali-metal poly(styrene sulfonate) (PSSM) gels having different degrees of sulfonation in aqueous organic solvent mixtures [water plus methanol, ethanol, 2-propyl alcohol, t-butyl alcohol, dimethyl sulfoxide (DMSO), acetone, acetonitrile, tetrahydrofuran, or dioxane]. With an increasing organic solvent concentration, most gel systems, except for DMSO, showed a volume phase transition. The transition abruptly occurred without significant deswelling in the lower solvent concentration region. Such swelling behavior contrasted with that of other common charged gel systems, including alkali-metal polyacrylate (PAAM) gels, which showed gel collapse after gradual deswelling with an increasing organic solvent concentration. The dielectric constant at the critical transition point (Dcr) for most mixed solvent systems decreased in the order of PSSK ≥ PSSCs ≥ PSSNa > PSSLi; that is, larger counterion systems were favorable for the transition. The counterion specificity also contrasted with our previous results for PAAM gels: PAANa > PAAK > PAALi ∼ PAACs. On the other hand, the solvent specificity for the PSSM gels was similar to that for the PAAM gels; the higher the dielectric constant was of the organic solvent, the higher the Dcr value was at which the transition occurred. These specificities were examined on the basis of the solvation properties of the counterions and polymer charged groups and the solvent properties such as the Gutmann–Mayer donor number and acceptor number. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1166–1175, 2007

The reaction of copper with benzyl bromides in dipolar aprotic solvents has been studied. There are no linear or other simple relations between e, 1/e, Y, P, n, and the rate of reaction. The activity of the solvent is determined by donor number (DN) in reaction under consideration. The kinetic and thermodynamic parameters of the reaction of copper with benzyl bromide in dimethyl sulfoxide (DMSO) have been clarified. Hammett plots of log (k/k°) vs. the substituent constant σ gave good correlations (ρ = 0.18, Sρ = 0.02, r = 0.961 in dimethyl sulfoxide and ρ = 0.21, Sρ = 0.02, r = 0.947 in dimethylacetamide (DMAA)). The structure of the organic group has little effect on the rate of reaction of benzyl bromide with copper. The Hammett ρ value also depends on DN. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 496–501, 2005

An electron-rich monovalent boron compound is used as a Lewis base to prepare adducts with Group 13 Lewis acids using both its boron and nitrogen sites. The hard Lewis acid AlCl3 binds through a nitrogen atom of the Lewis base, while softer Lewis acids GaX3 (Cl, Br, I) bind at the boron atom. The latter are the first noncluster Lewis adducts between a boron-centered Lewis base and a main-group Lewis acid.

Among the 'beyond Li-ion' battery chemistries, nonaqueous Li-O$_2$ batteries have the highest theoretical specific energy and as a result have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O$_2$ batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than four-fold) in Li-O$_2$ cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using $^7$Li nuclear magnetic resonance and modeling, we confirm that this improvement is a result of enhanced Li$^+$ stability in solution, which in turn induces solubility of the intermediate to Li$_2$O$_2$ formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anti-correlated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g. Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation., Comment: 22 pages, 5 figures and Supporting Information

The present article demonstrates the effect of different solvents used in the preparation of electrolyte on the photoelectrochemical characteristics of dye sensitized solar cells (DSSCs) aged under heat (60 degrees C) and illumination for 60 days. The study has been carried out with four different solvents: 3-methoxypropionitrile (MPN), N-methyl-2-pyrrolidone (NMP), propylene carbonate (PC) and gamma-butyrolactone (GBL) which differ in terms of donor number, viscosity and dielectric constant. For DSSCs with electrolytes based on MPN, PC and GBL as solvents, performance decreases with time. In contrast, for DSSC with NMP as solvent in electrolyte, increase in JSC and hence, efficiency up to 15 days has been observed followed by a gradual decrease, but remaining above its initial value after 60 days. However, VOC of such cell decreases with time. There are two possible causes for the above observations. Desorption of NMP molecules from titania surface occurred with aging. Secondly, zinc ions leached into the electrolyte following reaction of NMP with sealant were adsorbed on titania surface. The causes behind aging behavior of cells prepared with different solvent based electrolytes have been analyzed using electrochemical impedance analysis of DSSCs, energy-dispersive X-ray spectroscopy (EDS) of photoanodes and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) of electrolyte containing sealant sample which had also undergone aging under similar condition. (C) 2015 Elsevier Ltd. All rights reserved.

Herein we report the characteristics of a lithium-oxygen battery using a solid polymer membrane as the electrolyte separator. The polymer electrolyte, fully characterized in terms of electrochemical properties, shows suitable conductivity at room temperature allowing the reversible cycling of the Li-O2 battery with a specific capacity as high as 25,000 mAh gC−1 reflected in a surface capacity of 12.5 mAh cm−2. The electrochemical formation and dissolution of the lithium peroxide during Li-O2 polymer cell operation is investigated by electrochemical techniques combined with X-ray diffraction study, demonstrating the process reversibility. The excellent cell performances in terms of delivered capacity, in addition to its solid configuration allowing the safe use of lithium metal as high capacity anode, demonstrate the suitability of the polymer lithium-oxygen as high-energy storage system.

There has been speculations on the structures of TiF4 polymeric complexes {TiF4L}n (L = molecular donor) for several decades, however no structurally characterized examples have been reported. In this work the complex {TiF4(PhCN)}3 was isolated from a solution of TiF4 in PhCN (donor number DN = 11.9 kcal mol−1) as well as from the mixtures PhCN/CH2Cl2 and PhCN/toluene and characterized by X-ray, IR, NMR, EI-MS. The structure of the complex {TiF4(PhCN)}3 can be regarded as formed by combining three face-TiF3(PhCN)(μ-F) units, containing octahedrally coordinated titanium centers surrounded by three terminal fluorine atoms on the face of the octahedron and the bridging fluorine atoms in cis-positions with respect to each other. The structure of {TiF4(PhCN)}3 represents the first example of a trimeric pseudo pentahalide MX4L (M = Ti, Zr, X = halogen, D = ligand), a class of potentially interesting Lewis acids. The characterization of {TiF4(PhCN)}3 by 19F NMR revealed that in solution it dissociated to a mixture of [TiF3(PhCN)3]+, TiF4(PhCN)2 and oligomers including [Ti4F18]2− and {TiF4(PhCN)}n. The existence of oligomeric complexes containing face-{TiF3(PhCN)3−n(μ-F)n} (n = 1–3) fragments was established by one- and two-dimensional variable temperature 19F NMR. In contrast, TiF4 has a low solubility in SO2, because the donor strength of SO2 (DN = 6.5 ± 2.2 kcal mol−1) is too weak to fully convert polymeric TiF4 into soluble TiF4–SO2 donor–acceptor adducts. TiF4 and MeCN (DN = 14.1 kcal mol−1) formed only the molecular complex TiF4(MeCN)2, characterized by preliminary X-ray structure, IR and EI-MS. Thus mononuclear donor–acceptor complexes TiF4L2 can only be isolated from MeCN and stronger basic solvents.

Intermolecular interactions between water and N,N-dimethylformamide (DMF) in their mixtures were investigated by Raman spectroscopic and X-ray diffraction methods and by molecular orbital calculations. The Raman spectroscopic and X-ray diffraction measurements indicated the formation of water-DMF associates or clusters in the mixtures. Theoretical calculations for the electron density of H2O-HOH-OH2, of electron density on the oxygen atom of the water molecule in the DMF-HOH-DMF associate due to the accumulation of electrons transferred from DMF to the oxygen atom of the terminal water molecule. The increase resulted in a larger donicity of the terminal H2O compared to normal water. Although the donor number DN of the water molecule in the DMF-H2O-DMF associate was not determinable, it was estimated to be DN ∼ 30 from the behavior of the preferential solvation of the cobalt(II) ion in water-DMF mixtures.

In the study of the all-uranium redox-flow battery with a high efficiency, electrochemical investigations of the negative electrode reaction, i.e. U(IV)/U(III) of uranium β-diketone complexes, is necessary in aprotic solvents. In our recent studies, the uranium(IV) acelylacetonate, known to show the simplest voltammograms due to a quasi-reversible U(IV)/U(III) reaction at −2.6 V versus Fc/Fc+ in the solvent with the small donor number, shows more complicated voltammograms in the solvents with the larger donor numbers such as dimethyl sulfoxide (DMSO). For U4+ ion without acetylacetone in such solvents, several researchers reported an electrodeposition at around −1.6 to −2 V versus Fc/Fc+, whereas its details have not known at all. Therefore in this study, the electrode reactions of the U(IV)/U(III) and the U(III)/U(0) reaction of U(dmso)8(ClO4)4 were investigated by direct monitoring of weight changes of a Au electrode during potential sweeps by using the EQCM, as well as the HMDE. Also, an inhibition of the uranium electrodeposition by an addition of the acetylacetone was investigated.

The possibility of simultaneous elimination of intra-and intermolecular energy losses was investigated by the example of complexes of Tb3+ with pyrazole derivatives—pyrazolones-5 and pyrazole-5-carboxylic acids. Intramolecular energy losses were eliminated by adding a solvent with a high donor number (dimethyl sulfoxide (50 vol %), and intermolecular energy losses, by sorbing complexes on a polymer matrix (polymethylmethacrylate). As a result of elimination of these energy losses, the luminescence intensity of complexes of Tb3+ with the ligands studied increased from 3.8 times to two orders of magnitude.

The peculiarities have been studied of silver organosol formation in the breakdown of Ag(I) complex (synthesized by us) with 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]-acetic acid in solvents (dimethyl formamide, methanol, ethanol, propanol-2, butanol-1) of a high donor number (DN = 27–34). The dispersiveness and assembly peculiarities of silver nanoparticles in organosols were examined by means of absorbance spectroscopy, TEM and AFM. The organosol stability essentially depends on the nature of the dispersive medium, and on whether water and/or oxygen are present therein. The Ag(I) complex was shown to be a promising solid precursor in production of silver nanoparticles. Employing this precursor a new method of forming silver nanoparticles in polyelectrolyte capsule walls is proposed.

In the present work, femtosecond transient absorption spectroscopy (fs-TAS) has been employed to investigate the electron injection efficiency (EIE) both from the singlet and triplet excited states of a well-known ruthenium dye (N719) to the conduction band (CB) of nanostructured TiO(2) in presence of three different organic solvents [γ-butylactone (GBL), 3-methoxypropionitrile (MPN), and dimethylformamide (DMF)] with different donor numbers (DNs) and dipole moments (DMs). The DM and DN of a solvent modulates the CB edge energy of TiO(2), and this effect reflects well in the fs-TAS results, which shows an EIE trend following the order GBL≥MPN≫DMF, that is, highest in GBL and lowest in DMF solvent environments. Fs-TAS results indicate a lower contribution of electron injection from both the singlet and triplet states in DMF, for which the dominant adsorption of DMF molecules on the TiO(2) surface seems to play an important role in the mechanism.

The structure of the double electric layer (DEL) on a liquid dropping Sn-Ga electrode containing 8 at. % of Sn is studied in acetonitrile (AN) solutions of electrolytes. It is shown that the transition from aqueous to AN solutions of electrolytes makes it possible to expand the region of investigation of parameters of DEL on an Sn-Ga electrode from negative charges to a zero charge and to small positive charges. As follows from the obtained data, throughout the entire interval of charges studied, an excess, as compared with an Hg electrode, chemisorption interaction (Sn-Ga)-AN is absent. It is established that the distance of the closest approach of AN dipoles to an ionic core increases upon going from Hg to Sn-Ga to Ga. The Ga, Bi-Ga, and Sn-Ga electrodes, which possess close values of the “electrochemical work function,” are used as an example to show that the metal-solvent chemisorption interaction increases with decreasing distance of the closest approach of its dipoles to the ionic core of the metal. The effect of this factor becomes stronger as the donor number of the solvent increases.

To understand solvation in room temperature ionic liquids (RTILs), an FT-EPR spectrum of α-hydroxydiphenylmethyl (HDPM) radical was measured in several RTILs of tert -alkylammonium or alkylimidazolium salts with anions of PF 6 - , BF 4 - , (CF 3 SO 2 ) 2 N − , CF 3 SO 3 - , WO 4 2 - , Cl − and Br − . The hyperfine coupling constant of the hydroxyl proton depends on Gutmann’s donor number of the anions, while the constants of phenyl α-protons are essentially the same for these RTILs. This result suggests the electron donor character of anions is important in HDPM solvation in RTILs through the anion-OH group hydrogen-bond.

Drago’s acid–base approach was used to quantify the hydrogen bonding interactions in solvent swelling of cellulose fibers. The fiber swelling was correlated with acid–base, dispersive interactions and solvent molar volume. The acid–base interaction potentials of solvents were expressed in terms of their electron pair donor and acceptor numbers. The acid–base interaction terms of cellulosic materials were determined by using: (1) Flory–Huggins; (2) multiple regression models. We have used the swelling data of Mantanis and coworkers, which were based on the equilibrium liquid holding capacities of various compressed fibers in water and series of organic solvents. According to our interpretations, acid–base interactions and molar volume parameters were the major contributors to the overall solubility parameter. Acid–base interaction terms were balanced in alpha-cellulose sample. However spruce wood and sulfite pulp samples were more acidic than basic and therefore swollen better in organic basic solvents. For a good swelling behavior solvent must have high electron pair donor number/acceptor number ratio and high electron pair donor number–acceptor number difference.

Structural analyses of UO2(NO3)2L2 [L = N-n-butyl-2-pyrrolidone (NBP), N-cyclohexylmethyl-2-pyrrolidone (NCMeP), and 1,3-dimethyl-2-imidazolidone (DMI)] have been carried out using X-ray diffraction method. These uranyl complexes were found to have a hexagonal bipyramidal structure. The bond distances (A) of U O and U–O(ligand), and bond angles (°) of U–O–C(carbonyl) are determined as follows: 1.774(2), 2.374(2), and 137.6(2) for UO2(NO3)2(NBP)2; 1.770(1), 2.383(2), and 135.3(1) for UO2(NO3)2(NCMeP)2; 1.771(2), 2.361(2), and 143.3(2) for UO2(NO3)2(DMI)2. In uranyl nitrate complexes with cyclic amides such as 2-pyrrolidone, urea, and caprolactam derivatives, a linear correlation was found to hold between U–O(ligand) bond distances and U–O–C(carbonyl) bond angles. Vibrational frequencies of UO2(NO3)2L2 have also been measured by IR and Raman spectrophotometers. Using relationships between vibrational frequencies of O U O bonds and donor numbers (DNs) of ligands, it was found that donicities of N-substituted-2-pyrrolidones (Me, Et, Bu, cyclohexyl, and cyclohexylmethyl) are in the range of 26–29, and the DN of 1,3-dimethyl-2-imidazolidone was estimated as 27.8.

Mobility of the electroosmotic flow (mu(EOF)) in fused-silica capillaries strongly depends on the nature of the background electrolyte. In this study, 27 solvent systems were investigated, namely water, methanol, ethanol, 2-propanol, 1-butanol, acetonitrile (MeCN), formamide, N-methylformamide (NMF), N,N-dimethylformamide and dimethyl sulfoxyde, as well as 8 hydroorganic and 9 organic mixtures. For each system, six mu(EOF) were determined at a different ionic strength in basic conditions, and an absolute electroosmotic flow mobility (mu(EOF,0)) was extrapolated according to the Debye-Huckel Onsager model. The obtained mu(EOF,0) values were correlated with the solvent's relative permittivity (epsilon) and viscosity (eta). A good correlation (r2=0.867) between mu(EOF,0) and the solvent's epsilon/eta ratio was demonstrated, except for two solvents (MeCN and NMF). Furthermore, the donor number (DN) of a solvent took into account the possible zeta potential modification in the electric double layer near the capillary wall. Consequently, the relationship between mu(EOF,0) and epsilon/(eta x DN) was superior, with a r2 of 0.943 for 10 pure solvents.

Mixed copper(II) chelates, [Cu(trop/hino)(tmen)]B(C 6 H 5 ) 4 , were prepared with a tropolonato or hinokitiolato ligands (trop/hino) and N , N , N ′, N ′-tetramethylethylenediamine (tmen). These chelates were, as expected, quite similar to the corresponding acetylacetonato analog [Cu(acac)(tmen)]B(C 6 H 5 ) 4 , being fairly soluble in a large number of solvents and remarkably solvatochromic in them. They were also useful as excellent Lewis basicity indicators in solution because their d–d bands continuously shift to red in wider ranges with increasing DN (donor number) of solvent. The examination on addition of various anions to these solvatochromic systems led to a quantitative view of the competition between solvent molecule and anion for coordination to metal center.

Eight 3-arylallyl alcohols were prepared, and their OH stretching frequencies were measured in twenty non-HBD solvents at room temperature. The observed stretching bands were highly sensitive to the nature of the solvents. Multiple parameter equations were applied to investigate the solvent effect on the O-H stretching frequency. The most significant solvent parameters were the nucleophilicity parameter and the Gutmann donor number, while the electrophilicity parameter was not significant

The electro synthesis of polythiophene film from 2,2′-bithiophene monomer was investigated using different electrochemical techniques. The stability and electrical conductivity of the prepared film were studied. The most stable polythiophene film which also show slow relaxation (lowest relaxation time) was obtained using a galvanostatic technique in acetonitrile solvent with TBAPF 6 as supporting electrolyte at 5 °C. As the donor number of the solvent increases, the relaxation time decreases. The relaxation time is also sharply affected by temperature.

The complexation reactions between Mg 2 + , Ca 2 + , Sr 2 + and Ba 2 + cations with macrocyclic ligand, dibenzo-24-crown-8 (DB24C8) were studied in acetonitrile-dimethylformamide (AN-DMF) binary mixtures at different temperatures using the conductometry method. In all cases, DB24C8 forms 1:1 complexes with these cations. The values of stability constants of complexes which were obtained from conductometric data, show that the stability of complexes is affected by the nature and composition of the solvent. In many cases, the stability constants of complexes in these solvent systems increase with increasing the concentration of acetonitrile which has a lower donor number than dimethylformamide. However, in the case of complex formation between Mg 2 + and Sr 2 + cations with DB24C8, an anomalous behaviour was observed for the stability constants (LogK f ) with increasing the mole fraction of acetonitrile in AN-DMF binary mixtures at all temperatures. A non-linear behaviour was observed for variation of LogK f of the metal ion complexes vs the composition of the mixed solvents. This behaviour may be related to heteroselective solvation of cations and also solvent-solvent interactions in these binary systems. The obtained results show that the order of selectivity of DB24C8 ligand for the metal cations in different concentrations of acetonitrile in AN-DMF binary systems is: Ba 2 + > Sr 2 + > Ca 2 + > Mg 2 + , but a reversal in selectivity is observed in a certain composition of the mixed solvents. The values of thermodynamic parameters (ΔH° c and ΔS° c ) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van't Hoffplots. The results show that in most cases, the complexation reactions are enthalpy destabilized but entropy stabilized, and the values of these thermodynamic parameters are influenced by the nature and composition of the mixed solvents.

Dinuclear tris(acetylacetonato)ruthenium(III) complexes bridged by one sulfur atom (1) or two sulfur atoms (2) at the γ-position of the acetylacetonate have been synthesized by the reactions of tris(acetylacetonato)ruthenium(III) with SCl2 or S2Cl2. The molecular structure of 2 has been determined by single crystal X-ray diffraction study. The cyclic voltammograms of both the dinuclear complexes exhibit two one-electron reduction waves in acetonitrile (AN), dichloromethane (DM), benzonitrile (BN), and N,N-dimethylformamide (DMF). While the complex 1 exhibited two one-electron oxidation waves in AN, DM, and BN, complex 2 showed only irreversible waves in all the solvents. The comproportionation constants (Kc) for mixed-valence states of both RuII/RuIII and RuIII/RuIV were calculated from the redox potentials of dinuclear complexes. The values of log10Kc (RuII/RuIII) (for complexes 1 and 2) and log10Kc (RuIII/RuIV) (for complex 1) were between 1.35 and 3.55. These values are not so large and hence, the complexes may be classified as class II in the Robin and Day classification. Although no relationship could be found between Kc and the dielectric constant of the solvent, there exists a correlation between donor number (DN) of the solvent and log10Kc values.

Oxidation of dimethyl sulfoxide with benzoyl peroxide in some dipolar aprotic solvents and superbasic media was studied. The kinetic parameters were correlated with the main physicochemical characteristics of solvents. The oxidation rate grows with increasing donor number and polarizability of the solvent. A two-step scheme of dimethyl sulfoxide oxidation with benzoyl peroxide in superbasic media was suggested, involving preliminary cleavage of the peroxide to perbenzoate with the base. In the reaction, sodium tert-butylate is preferable over sodium hydroxide.

For [PMo12O40]3−, the presence of Li+ produced a two-electron wave at nearly the same potential as the first one-electron wave in acetonitrile or acetone. The voltammetric behavior of [PMo12O40]3− in a binary mixture of acetonitrile and solvent S was compared with those in a mixture of acetone and S. When the donor number (DN) of S>20, the first two-electron wave was converted into one-electron waves in such binary mixtures. The conversion occurred at lower mole fractions of S in an acetonitrile+S mixture than in an acetone+S mixture. The 7Li NMR results showed that the preferential solvating ability of Li+ with S was greater in the former mixture. A linear relationship was found between the iso-solvation point xiso(S) and the reciprocal of the difference between the DNs of S and acetonitrile, which gave the basis to explain the anomalies observed for a mixture of acetonitrile and H2O.

The visible absorption spectra of CoCl2 in binary mixtures of acetone, dmf, dma and dmso with H2O show the existence of configuration equilibria between tetrahedral (T) and octahedral (O) species. Linear correlations between the values of log K (K = [O]/[T]) and the mole fraction of H2O, χ w, have been observed in all the systems under study; their slopes decrease linearly with an increase of the donor number, DN, of the organic component of the mixture. The formation of octahedral species is enthalpy favoured but entropy disfavoured. It was found that both ΔH and ΔS values change linearly with χ w and the slopes of these relationships depend clearly on the DN values.

The title compound has been first synthesized and fully characterized as both tetraphenylborate and perchlorate salt. Its 300-900 nm absorption spectrum, recorded in nitromethane, water, and dimethyl sulfoxide, reveals the peculiar existence of two distinct bands whose intensities depend on the solvent donor number. This feature can be attributed to two separate metal-to-ligand charge-transfer transitions, in agreement with the theoretical predictions obtained by extensive configuration interaction calculations, which take into account the solvent effects. The calculation of the potential energy curves of the ground and excited states along the Ru-tetrazine coordinate allows the interpretation of the relative intensities of the observed bands, as well as the interpretation of their line-shape profiles.

The spin interconversion equilibrium involving the [Ni(II)(cyclam)]2+ complex has been investigated in a variety of polar solvents, at varying temperatures. The greater the donor tendencies of the solvent, the higher the endothermicity of the high-to-low-spin conversion. In particular, a positive linear relationship exists between DeltaHdegrees and Gutmann's Donor Number (DN). In the same way, higher donor tendencies of the solvent favour the occurrence of the Ni(II)-to-Ni(III) oxidation process and negative linear relationship has been found between the E1/2(Ni(III)/Ni(II)) and DN. General behaviour is related to the intensity of the metal-solvent axial bonds in the octahedrally elongated cyclam complexes (of both Ni(II) and Ni(III)).

The equilibrium constants for dimerization of three different carboxylic acids in near-critical and supercritical carbon dioxide and ethane at various temperatures and densities are presented. Fourier transform infrared spectroscopy was used to determine the equilibrium constants by examining the CO stretching frequencies of the monomer and dimer of the acids in solution. The equilibrium constants for formic acid, propionic acid, and trifluoroacetic acid decrease with temperature for both ethane and CO2 solvents and strongly depend on CO2 solvent density. The modified lattice fluid hydrogen-bonding (MLFHB) model was used to interpret this density dependence of the equilibrium constants. The density dependence provides evidence for specific solvent−solute interactions between CO2 and the carboxylic acid functional group, which is attributed to strong Lewis acid−Lewis base interactions. Since carboxylic acids contain both a Lewis acid and a Lewis base moiety, the examination of a strong acid such as trifluo...

Azobenzene-conjugated mononuclear and dinuclear terpyridyl complexes of Co(II), Co(III), and Fe(II) were synthesized, and their photoisomerization behavior was investigated. Co(II) and Co(III) complexes, [tpyCo(tpy-AB)]X(n) and [(Cotpy)(2)(tpy-AB-tpy)]X(n) (tpy-AB = C(15)N(3)H(10)-C(6)H(4)-N=NC(6)H(5), tpy-AB-tpy = C(15)N(3)H(10)-C(6)H(4)-N=NC(6)H(4)-C(15)N(3)H(10), X = PF(6) or BPh(4)), exhibit trans-to-cis photoisomerization by irradiation at 366 nm, and this behavior is dependent on solvents and counterions. For the Co(II) complexes, BPh(4) salts undergo cis-to-trans isomerization in propylene carbonate by both photoirradiation with visible light (435 nm) and heat, indicating that reversible trans-cis isomerization has occurred. [Co(tpy-AB)(2)](BPh(4))(2) shows a two-step trans-to-cis isomerization process. The trans-cis isomerization behavior of Co(III) complexes was observed only in the solvents with a low donor number such as 1,2-dichloroethane. Fe(II) complexes, [tpyFe(tpy-AB)]X(n) (X = PF(6) or BPh(4)), exhibit slight trans-to-cis photoisomerization due to the energy transfer from the azobenzene moiety to Fe(tpy)(2) moieties.

Vanadium(IV) and (V) complexes (VO(sal-ae)) with Schiff bases prepared from 2-aminoethanol and salicylaldehyde and its derivatives have been synthesized and characterized in solid and in solution by EPR, IR, and UV–Vis spectroscopy. The complexes of both V(IV) and V(V) contain bridges (VOV) by alkoxy oxygens(oxo) in the solid state. The complexes of V(IV) in dichloromethane are binuclear,in which two alkoxy oxygens serve as bridges between the two metal atoms. They are mononuclear with one solvent ligated in the equatorial plane in each complex in dimethyl sulfoxide and methanol. The extent of the formation and the stability of organic hydroperoxide complexes of V(V) prepared from the V(IV)–Schiff base complexes increase with decreasing donor number of the solvent. The difference in electron-donating and withdrawing ability of the substituent groups affects the A‖ values for the V(IV)–Schiff base complexes in DMSO.

The effect of donor number of solvent on the conductivity behaviour of gel electrolytes has been studied. Liquid electrolytes were prepared by dissolving salicylic acid in solvents based on ethylene carbonate (EC), propylene carbonate (PC) and dimethylformamide (DMF) with different donor number and dielectric constant values. Three different polymers, polymethylmethacrylate (PMMA), polyacrylonitrile (PAN) and polyethylene oxide (PEO), were used as the gelling polymer. The conductivity of polymer gel electrolytes has been found to be higher than the corresponding liquid electrolytes, i.e. σ (gel)>σ (liquid). This has been explained to be due to an increase in carrier concentration by the dissociation of undissociated salicylic acid/ion aggregates present in the electrolytes with the addition of polymer. However, the relative increase in conductivity observed with the addition of different gelling polymers has been found to depend upon the donor number of the solvent used.