Anion Pair Research Articles

The effects of dication symmetry on ionic liquid electrolytes in supercapacitors

The effects of dication symmetry on the structure and capacitance of the electrical double layers (EDLs) of dicationic ionic liquids (DILs) near graphene electrodes were investigated by molecular dynamics (MD) simulation in this work. Symmetrical 1-hexyl-3-dimethylimidazolium di[bis(trifluoromethyl)imide]([C6(mim)2](Tf2N)2) and asymmetrical 1-(1-trimethylammonium-yl-hexyl)-3-methylimidazolium di[bis(trifluoro-methanesulfonyl)-imide] ([C6(tma)(mim)](Tf2N)2) were both employed. Radial distribution function (RDF) analysis of the two DILs revealed a shorter distance between the cation–anion pairs in symmetrical [C6(mim)2](Tf2N)2), which was attributed to the closely packed imidazolium ring-anion pairs. In contrast, the trimethylammonium head groups and anions exhibit a relatively longer distance, but a stronger correlation in asymmetrical [C6(tma)(mim)](Tf2N)2. In addition, it was illustrated that more symmetrical DIL ions in EDLs are distributed near graphite electrodes and exhibit closer distances to the electrode, which is most probably due to the parallel orientation of imidazolium rings, reducing the distance between the cation and the graphene. In contrast, asymmetrical DILs, with one trimethylammonium head group and one imidazolium ring in the dications, are loosely packed due to their tilting orientation near graphene surfaces. However, the capacitance–potential (C–V) curves of the two DILs are almost the same, regardless of the opposite sign of potential of zero charge (PZC), indicating the insignificant influence of dication symmetry on the capacitance of DIL-based supercapacitors.

Stability and electronic structures of isoelectronic impurity complexes in Si: First-principles study

The stability and electronic structures of various isoelectronic cation+anion pairs in Si were studied by first-principles calculations. It was shown that the nearest-neighboring substitutional configuration is the most stable structure for most cation+anion pairs, while B+N, Mg+O, and Be+O pairs preferentially occupy a single Si site owing to the small atomic radii of B, N, and O atoms. We found that only Al+N, Ga+N, and In+N pairs produce electron-unoccupied weakly localized states in the band gap of Si, reflecting the large negativity of N atoms. We also showed that single N doping produces N+N pairs and that such pairs induce no electronic states in the band gap of Si. Therefore, the codoping of Al and N atoms is essential to produce an electronic state in the Si band gap and increase the tunneling current in Si tunneling field-effect transistors.

ChemInform Abstract: Pyridinium Saccharinate Salts as Efficient Recyclable Acylation Catalyst: A New Bridge Between Heterogeneous and Homogeneous Catalysis.

It is important to find a way for separation of concerned chemicals from product mixture after reaction, in order to avoid spreading harmful chemicals to society. The homogeneous nature of DMAP-catalyzed acylation still suffers from the problems of catalyst separation and/or residual DMAP contamination. DMAP causes acute dermal toxicity, whereas the corresponding DMAP salt exhibits only slight irritation to the skin. Very recently, we found that the DMAP saccharinate salt is also great recyclable catalyst, whose acylation of alcohols has been successfully and effectively carried out 10 times without loss in activity. This report covers our comprehensive studies on using the pyridinium saccharinate salts as efficient recyclable acylation catalysts including 4-N,N-dimethylaminopyridinium saccharinate (A), 4-(1-pyrrolidinyl) pyridinium saccharinate (B), 2-N,N-dimethylaminopyridinium saccharinate (C), and pyridinium saccharinate (D). Their structure and reactivity have been studied. The salts A, C, and D contain very interesting seven-membered synthon showing multiple H-bonding interactions for pair of pyridinium cation and saccharinate anion in the solid state. The salt B exhibits H-bonding interaction of N(sac) … H–N(py) in the solid state, instead of seven-membered synthon. The catalytic reactivity studies show that salts A and B are both very effective, with salt B even better in reactivity, and are both recyclable in the esterification of a variety of alcohols, under solvent-free and base-free conditions at room temperature.

High Throughput Approach to Accelerate Electrolyte Discovery for Post Li-Ion Batteries

Transforming transportation and electricity grid with high performance, low cost energy storage require development of post Li-ion technology and innovations in electrodes and electrolytes, alike. A non-aqueous multivalent (e.g., Mg2+, Ca2+ and Zn2+) metal cell is one of the potential candidates for a post-lithium-ion battery. The theoretical volumetric capacity of a metal anode coupled with the lack of dendrite formation at a multivalent metal anode provide an attractive opportunity in energy storage.1 The ability of Mg batteries to provide much higher volumetric capacity, particularly on the anode side where the Mg metal can theoretically provide 3833 mA h/cc as compared to the Li counterpart graphite (∼ 800 mA h/cc) at a lower cost makes the technology an attractive candidate for future batteries. On the other hand Zn metal anodes coupled with a reversible intercalation cathode chemistry have a number of promising features: (1) highly efficient (≥ 99%) reversible Zn deposition on Zn metal anode in high performance nonaqueous Zn electrolytes (e.g., high anodic stability (maximum ∼ 3.8 V) and ionic conductivity) (2) relatively lower activation barrier energy for migration of Zn2+ ions in a variety of cathode materials (e.g., FePO4, NiO2, and V2O5) (3) similar ionic radius compared with Li+ and Mg2+ ions (4) much higher volumetric capacity compared to other multivalent metals, such as Mg and Ca. However, development and commercialization of multivalent batteries require not only improved electrode discovery and development but also novel electrolytes, which are compatible with both the multivalent metal as well as the multivalent cathode. Thus a fundamental understanding of molecular level properties of these electrolytes is required to improve the electrochemical stability and the charge transfer properties. An automatic High-throughput computational infrastructure has been constructed for the electrolyte genome project supported by the US Joint Center for Energy Storage Research (JCESR) coupled with experimental analysis2. In this work, we present a multi-scale modelling approach for multivalent salts in various solvents. We uncover a novel effect between concentration dependent ion pair formation and anion stability at reducing potential, e.g., at the metal anode1. We elucidate systematic correlations between molecular level interactions and composite electrolyte properties, such as electrochemical stability, solvation structure, and dynamics. We find that Mg electrolytes are highly prone to ion pair formation, even at modest concentrations, for a wide range of solvents with different dielectric constants, which have implications for dynamics as well as charge transfer. Specifically, we observe that, at Mg metal potentials, the ion pair undergoes partial reduction at the Mg cation center (Mg2+→Mg+), which competes with the charge transfer mechanism and can activate the anion to render it susceptible to decomposition. Specifically, TFSI− exhibits a significant bond weakening while paired with the transient, partially reduced Mg+. We uncover the origin of anodic stability for a range of nonaqueous zinc electrolytes. By examination of electrochemical, structural, and transport properties of nonaqueous zinc electrolytes with varying concentrations, it is demonstrated that the acetonitrile−Zn(TFSI)2 , acetonitrile− Zn(CF3SO3)2 , and propylene carbonate− Zn(TFSI)2 electrolytes can not only support highly reversible Zn deposition behavior on a Zn metal anode (≥ 99% of Coulombic efficiency) but also provide high anodic stability (up to ∼ 3.8 V vs Zn/Zn2+ ).3 The combination of multi-scale modeling with experimental techniques provides unprecedented insight into the origin of the electrochemical, structural, and transport properties in multivalent electrolytes.

Enthalpies of solution of 1-ethyl- and 1-butyl-3-methylimidazolium based ionic liquids in tetrahydrofuran and chloroform at 298.15 K: Thermochemical proton acceptor scale of anions

In this work the thermodynamics of intermolecular interactions for imidazolium based ionic liquids in solutions of proton donor solvent chloroform and proton acceptor solvent tetrahydrofuran was studied using solution calorimetry technique. Enthalpies of solution of 1-ethyl- and 1-butyl-3-methylimidazolium based ionic liquids with tetrafluoroborate, methylsulfate, ethylsulfate, butylsulfate, dicyanoamide, trifluoromethanesulfonate, thiocyanate anions were measured in two solvents over concentration range 0.18-3.60mmolkg−1 at 298.15K. Enthalpies of transfer from tetrahydrofuran to chloroform derived from experimental data were exothermic for all studied ionic liquids. Proton acceptor scale of ionic liquids as solutes was proposed on the basis of thermochemical data. Enthalpy of hydrogen bonding of ionic liquids with proton donor solvent chloroform increases in the range of anions [BF4]−<[SCN]−<[TfO]−<[N(CN)2]−<[AlkSO4]−. At the same time these values remain constant for ILs with different length of alkyl group in cations and anions. Thermochemical proton acceptor scale of ILs in solution correlates well with COSMO-RS hydrogen-bonding energies in equimolar cation–anion pairs of ILs.

First-principles calculations of sulphur isotope fractionation in MX2 minerals, with M = Fe, Co, Ni and X2 = AsS, SbS

Iron, Co and Ni are first row transition metals and are all able to combine with S, As, and Sb to form disulphides, sulpharsenides and sulphantimonides, respectively, all of which exhibit substitutions of metal and metalloid elements in their structures. As an important tracer in the geochemistry of ore deposits, S isotope fractionation in sulphides can be used to analyse the ore-forming process and the source of ore-forming elements. However, there have been few studies of S isotope fractionation in sulpharsenides and sulphantimonides. Studying the isotope fractionation of the various members of this structural group can provide systematic information regarding S isotope fractionation in transition metal disulphides, sulpharsenides and sulphantimonides. In this paper, the S isotope fractionation parameters for Fe, Co and Ni sulpharsenides and sulphantimonides were calculated using first-principles methods based on density functional theory in the temperature range of 0–1000°C. Our calculations show that the order of heavy S isotope enrichment is arsenopyrite>cobaltite>gudmundite>costibite>gersdorffite>ullmannite. For sulphides with the same anion pair, the main factor affecting S isotope fractionation is the metal-sulphur bond strength. For most of the sulphides studied in this paper, S isotope fractionation arising from substitution of metalloid elements is much smaller than that of metal elements.

2-Amino-4-methylpyridinium 2-(4-nitrophenyl)acetate

In the title molecular salt, C6H9N2+·C8H6NO4−, the cation is protonated at its pyridine N atom. In the crystal, the anions are connected by a pair of C—H...O contacts into [100] chains, which generateR22(11) loops and these chains are linkedviaanother C—H...O contact which encloses anR24(10) loop. Adjacent anions and cations are connected through N—H... O hydrogen bonds, generating anR22(8) loop. Two pairs of anions and cations are linked by N—H...O hydrogen bonds, forming a tetramer with anR22(8) loop motif. The packing also features weak C—H...π and π–π [centroid-to-centroid distances = 3.8972 (11) and 3.9549 (10) Å] interactions, which result in a three-dimensional network.

COSMO-RS: An ionic liquid prescreening tool for gas hydrate mitigation

Recently ionic liquids (ILs) are introduced as novel dual function gas hydrate inhibitors. However, no desired gas hydrate inhibition has been reported due to poor IL selection and/or tuning method. Trial & error as well as selection based on existing literature are the methods currently employed for selecting and/or tuning ILs. These methods are probabilistic, time consuming, expensive and may not result in selecting high performance ILs for gas hydrate mitigation. In this work, COSMO-RS is considered as a prescreening tool of ILs for gas hydrate mitigation by predicting the hydrogen bonding energies (EHB) of studied IL inhibitors and comparing the predicted EHB to the depression temperature (Ŧ) and induction time. Results show that, predicted EHB and chain length of ILs strongly relate and significantly affect the gas hydrate inhibition depression temperature but correlate moderately (R=0.70) with average induction time in literature. It is deduced from the results that, Ŧ increases with increasing IL EHB and/or decreases with increasing chain length. However, the cation–anion pairing of ILs also affects IL gas hydrate inhibition performance. Furthermore, a visual and better understanding of IL/water behavior for gas hydrate inhibition in terms of hydrogen bond donor and acceptor interaction analysis is also presented by determining the sigma profile and sigma potential of studied IL cations and anions used for gas hydrate mitigation for easy IL selection.

Poly(ionic liquid) prepared by photopolymerization of ionic liquid monomers as quasi-solid-state electrolytes for dye-sensitized solar cells

Vinylimidazolium-typed poly(ionic liquids) (PILs) are prepared by photo-polymerization of ionic liquid monomers. Vinylimidazolium-based ionic liquid monomers with C4 and C8 alkyl tail length were synthesized via quaternization of 1-vinylimidazole with corresponding n-alkyl bromides. Polymerization was conducted at a 3wt.% of photoinitiators in these monomers using illumination of 36W LED light. In the same procedure, preparation of cross-linked PILs was performed in the presence of 15mol% of divinylimidazolium-based cross-linker. These PILs are characterized by using chemical structure, physical characteristics, and electrical conductivity. Electrical conductivity of C4-based PILs is greater than that of C8-based PILs, whereas linear PILs are higher than crosslinked PILs. Crosslinked PILs have higher glass transition and thermal decomposition temperatures as compared linear PILs. PILs consist of the repeating units of anion and cation pair. Its nature has moderate electronic conductivity, which is suitable use in gel-type or quasi-solid-state dye-sensitized solar cells (DSSCs). The linear PILs were incorporated in DSSCs obtaining an efficient quasi-solid-state cell to solve the leakage of liquid electrolyte in a liquid-type DSSC.

Pyridinium saccharinate salts as efficient recyclable acylation catalyst: a new bridge between heterogeneous and homogeneous catalysis

It is important to find a way for separation of concerned chemicals from product mixture after reaction, in order to avoid spreading harmful chemicals to society. The homogeneous nature of DMAP-catalyzed acylation still suffers from the problems of catalyst separation and/or residual DMAP contamination. DMAP causes acute dermal toxicity, whereas the corresponding DMAP salt exhibits only slight irritation to the skin. Very recently, we found that the DMAP saccharinate salt is also great recyclable catalyst, whose acylation of alcohols has been successfully and effectively carried out 10 times without loss in activity. This report covers our comprehensive studies on using the pyridinium saccharinate salts as efficient recyclable acylation catalysts including 4-N,N-dimethylaminopyridinium saccharinate (A), 4-(1-pyrrolidinyl) pyridinium saccharinate (B), 2-N,N-dimethylaminopyridinium saccharinate (C), and pyridinium saccharinate (D). Their structure and reactivity have been studied. The salts A, C, and D contain very interesting seven-membered synthon showing multiple H-bonding interactions for pair of pyridinium cation and saccharinate anion in the solid state. The salt B exhibits H-bonding interaction of N(sac) … H–N(py) in the solid state, instead of seven-membered synthon. The catalytic reactivity studies show that salts A and B are both very effective, with salt B even better in reactivity, and are both recyclable in the esterification of a variety of alcohols, under solvent-free and base-free conditions at room temperature.

A novel β-(oxy)alkyl radical during copper(I)-mediated stereoselective synthesis of (Z)-ene-1,4-diones in a reaction of 2,2,2-trichloro-1-phenylethanone

A novel β-(oxy)alkyl radical derived from trichloro methyl compound containing neither a suitably located C–C multiple bond nor a leaving group or a H-atom at the β-position of the radical in a reaction of 2,2,2-trichloro-1-phenyl-ethanone with 2mol equiv each of CuCl and bpy in refluxing DCE under a N2 atm underwent intramolecular heterolysis (just like formation of intact radical cation–anion pair) during stereoselective radical dimerization to Z-ene-1,4-dione along with small amount of reductive dechlorination product. The stereochemistry was established by X-ray diffraction spectroscopy of various solid crystalline products.

Crystal structures of three anhydrous salts of the Lewis base 1,8-di-aza-bicyclo-[5.4.0]undec-7-ene (DBU) with the ring-substituted benzoic acid analogues 4-amino-benzoic acid, 3,5-di-nitro-benzoic acid and 3,5-di-nitro-salicylic acid.

The anhydrous salts of the Lewis base 1,8-di-aza-bicyclo-[5.4.0]undec-7-ene (DBU) with 4-amino-benzoic acid [1-aza-8-azoniabi-cyclo-[5.4.0]undec-7-ene 4-amino-benzoate, C9H17N2 (+)·C7H6NO2 (-) (I)], 3,5-di-nitro-benzoic acid [1-aza-8-azoniabi-cyclo-[5.4.0]undec-7-ene 3,5-di-nitro-benzoate, C9H17N2 (+)·C7H3N2O6 (-), (II)] and 3,5-di-nitro-salicylic acid (DNSA) [1-aza-8-azoniabi-cyclo-[5.4.0]undec-7-ene 2-hy-droxy-3,5-di-nitro-benzoate, C9H17N2 (+)·C7H3N2O7 (-), (III)] have been determined and their hydrogen-bonded structures are described. In both (II) and (III), the DBU cations have a common disorder in three of the C atoms of the six-membered ring moieties [site-occupancy factors (SOF) = 0.735 (3)/0.265 (3) and 0.686 (4)/0.314 (4), respectively], while in (III), there is additional rotational disorder in the DNSA anion, giving two sites (SOF = 0.72/0.28, values fixed) for the phenol group. In the crystals of (I) and (III), the cation-anion pairs are linked through a primary N-H⋯Ocarbox-yl hydrogen bond [2.665 (2) and 2.869 (3) Å, respectively]. In (II), the ion pairs are linked through an asymmetric three-centre R 1 (2)(4), N-H⋯O,O' chelate association. In (I), structure extension is through amine N-H⋯Ocarbox-yl hydrogen bonds between the PABA anions, giving a three-dimensional structure. The crystal structures of (II) and (III) are very similar, the cation-anion pairs being associated only through weak C-H⋯O hydrogen bonds, giving in both overall two-dimensional layered structures lying parallel to (001). No π-π ring associations are present in any of the structures.

Contact Ion Pairs on a Protonated Azamacrocycle: the Role of the Anion Basicity.

A potassium-containing hexaazamacrocyclic dication, [M•H•K](2+), is able to add in the gas phase mono- and dicarboxylate anions as well as inorganic anions by forming the corresponding monocharged adducts, the structure of which markedly depends on the basicity of the anion. With anions, such as acetate or fluoride, the neutral hexaazamacrocycle M acts as an acceptor of monosolvated K(+) ion. With less basic anions, such as trifluoroacetate or chloride, the protonated hexaazamacrocycle [M•H](+) performs the unusual functions of an acceptor of contact K(+)/anion pairs. Graphical Abstract ᅟ.

Brief Determination of Standard Formal Potentials for the Transfers of Several Pairing Anions across the Nitrobenzene/Water Interface by Na(I) Extraction with 18-Crown-6 Ether

Extraction constants (Kex±) for the extraction of sodium salts (NaA) with 18-crown-6 ether (18C6) from water (w) into nitrobenzene (NB) were determined at 298 K, together with the determination of individual distribution constants (KD,A) of several pairing anions A−. The symbols Kex± and KD,A were defined as [NaL+]NB[A−]NB/([Na+][L]NB[A−]) at L = 18C6 and [A−]NB/[A−], respectively; the subscript “NB” shows the NB phase. Also, ion-pair formation constants for sodium 2,4-dinitrophenolate (NaDnp) and its ion pair complex with 18C6 in water were determined by potentiometry with a Na+-selective electrode. Standardized (S) KD,A values were briefly calculated from the following thermodynamic cycle: KD,A S = Kex±/KD,Na SKNaL,NB. Here, KD,Na S and KNaL,NB denote the standardized individual distribution-constant of Na+ into and a complex formation constant for NaL+ in the NB phase, respectively. Moreover, equilibrium potential differences (Δφeq) at the NB/w interface were estimated from the relation Δφeq = 0.05916log (KD,A S/KD,A) at 298 K. The Δφeq values of A− = F3CCO2 −, MnO4 −, ReO4 − and Dnp− were determined for comparison with the value of picrate ion. The plot of log Kex± versus Δφeq gave a positive correlation at (correlation coefficient)2 = 0.748.

Double-hole codoped huge-gap semiconductor ZrO2 for visible-light photocatalysis.

Double-hole doping is an effective approach to engineer the band structures of semiconductors for enhancing the photoelectrochemical performance. Here, we explore the anionic monodoping (i.e. N, C, and P) and codoping (i.e. N + N, C + S, and N + P pairs) effects on the electronic structures and photocatalytic activities of ZrO2 by performing extensive density functional theory calculations. Upon anionic monodoping, several unoccupied impurity states appear within the band gap, which may trap the photogenerated carriers and then reduce the photocatalytic efficiency. Remarkably, double-hole doping via introducing three anionic (N + N), (C + S), and (N + P) codoping pairs in ZrO2 can not only effectively narrow the band gap, but can also create several fully filled delocalized intermediate bands for preventing the recombination of the photogenerated electron-hole pairs. Moreover, the band edge positions matching well with the redox potentials of water and the improved visible light absorption ability indicate that the three examined codoped ZrO2 systems are promising photocatalysts for visible light water splitting. In short, double-hole doping via anionic pairs provides an effective path to tune the huge-gap semiconductor band structures and to develop high efficient catalysts for solar-driven water splitting.

Ion pair complexes and anion binding in the solution of a ditopic receptor.

The synthesis and crystal structures with alkali halides of a ditopic benzo-15-crown-5 bis-urea receptor have been presented. In addition, the anion binding properties of and its alkali metal complexes in solution are presented. A comprehensive single-crystal X-ray crystallographic study of , all together 13 crystal structures, including the ion pair complexes with NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, and RbI, give a detailed view of how behaves in the solid-state with different alkali halides depending on the size of the cation and anion. In the solid-state forms a 1 : 1 complex with a sodium cation and the anion is complexed as a contact (NaCl) or a separate ion pair (NaBr, NaI). With larger potassium and rubidium cations assembles into a 2 : 1 complex and forms a separated ion pair complex with the anion. Reflecting the crystal structures the forms a 1 : 1 complex with Na(+) in solution, and a 2 : 1 complex with K(+), which were verified by Job's plot analysis in 4 : 1 CDCl3/dimethyl sulfoxide. The binding strength of the monomeric [·Na](+) and the dimeric [2·K](+) toward chloride, bromide and iodide anions was studied by (1)H NMR titrations in 4 : 1 CDCl3/DMSO, and a clear turn-on effect of the cation complexation compared to the neutral receptor alone (Ka with for Cl(-), Br(-) and I(-) being 832, 174 and 32 M(-1), respectively) was observed. The monomeric [·Na](+) binds chloride 9, bromide 8, and iodide 12 times stronger than , while for the dimeric [2K](+) the corresponding increase in binding is 51 (Cl(-)), 84 (Br(-)), and 22 (I(-)) times with the same stoichiometric ratios as observed for the ion pair complexes in the solid-state.

A DFT study on the correlation between topology and Bader charges: Part IV, on the change of atomic charges in polymorphic transitions – A case study on CaCl2

Referring to the experimental results of high pressure experiments of Léger et al. (1998) we have calculated the energies of all phases observed for CaCl2 within the DFT formalism using the VASP package, and we have retrieved enthalpies and transition pressures. All phases can be considerably compressed or dilated without much change in energy. This energetic “softness” could even be quantified. We classify the high temperature TiO2-type structure and the PbCl2-type one at highest pressures as the energetically “softest” ones and the SrI2-type one as the “hardest”. We furthermore discuss the energy density (E/V) of the different phases and redefine it as a fictive cohesive pressure within these structures.Pursuing our earlier approaches we have analysed the charges of the atoms in the different CaCl2 phases and their change on compression or dilation. On comparing the gradients of the charge curves we define a sort of “charge hardness” which will generally depend on the type of cation–anion pair but also on their topological connection in the respective structures. We speculate that exhausting the “charge softness or hardness” of individual ions in such arrangements may initiate the structural reorganization at the transition pressures.

FT-Raman spectroscopy study of solvent-in-salt electrolytes**Project supported by the National Basic Research Program of China (Grant No. 2014CB932300), the National Natural Science Foundation of China (Grant Nos. 51222210, 51472268, and 11234013), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09010300).

Cation–anion interaction with different ratios of salt to solvent is investigated by FT-Raman spectroscopy. The fitting result of the C–N–C bending vibration manifests that the cation–anion coordination structure changes tremendously with the variation of salt concentration. It is well known that lithium-ion transport in ultrahigh salt concentration electrolyte is dramatically different from that in dilute electrolyte, due to high viscosity and strong cation–anion interaction. In ultrahigh salt concentrated “solvent-in-salt” electrolyte (SIS-7#), we found, on one hand, that the cation and anion in the solution mainly formed cation–anion pairs with a high Li+ coordination number (≥ 1), including intimate ion pairs (20.1%) and aggregated ion pairs (79.9%), which not only cause low total ionic conductivity but also cause a high lithium transference number (0.73). A possible lithium transport mechanism is proposed: in solvent-in-salt electrolytes, lithium ions’ direct movement presumably depends on Li-ion exchange between aggregated ion pairs and solvent molecules, which repeats a dissolving and re-complexing process between different oxygen groups of solvent molecules.

The configuration exchanging theory for transport properties and glass formation temperature of ionic liquids.

Understanding molecular motion in terms of molecular structure is an important issue for microscopic understanding of the nature of transport properties and glass transition, and for design of structured materials to meet specific demands in various applications. Herein, a novel molecular mechanism is proposed to connect macroscopic motion in ionic liquids with molecular structure via conformational conversions of the constituent ions or of the cation-anion pairs. New equations for description of relaxation time, diffusion coefficient, molar conductivity, and viscosity of ionic liquids are established. The equation parameters, which were determined from the temperature dependent heat capacities, self-diffusion coefficients, molar conductivities, and viscosities of typical ionic liquids, were used to produce predictions for the corresponding properties of other ionic liquids and for the glass transition temperatures of representative ionic liquids. All predictions are in nice agreements with the experimental results.

The group VA element non-compensated n–p codoping in CuGaS2 for intermediate band materials

Noncompensated n–p codoping by different element combinations has proven to be an effective approach to create intermediate bands (IBs) in wide band gap semiconductors. Here, we present a new noncompensated n–p codoping case by simultaneously substitute the cation and anion pair with the same element, which is implemented by using group VA element codoped CuGaS2 systems, within first-principles calculations. The results suggest that the M (N, P, As or Sb) element substitutional codoping on Ga and S sites will introduce partially filled and isolated IBs in the band gap, and that the optical absorption is enhanced in all of the M codoped systems compared with the host CuGaS2, due to the additional electron transition though IB. However, the stability analysis suggest that only P, As and Sb can enable stable IB material growth, and N will decompose the compound into more stable binary phase. Hence, M (P, As or Sb) codoped CuGaS2 materials are predicted as promising candidates in photovoltaic applications. Besides, the codoping method may also be used in other functional materials to obtain controllable doping.