Chemical bonding and electronic properties along Group 13 metal oxides.

CONTEXT: The present work provides a systematic theoretical analysis of the nature of the chemical bond in Al2O3, Ga2O3, and In2O3 group 13 cubic crystal structure metal oxides. The influence of the functional in the resulting band gap is assessed. The topological analysis of the electron density provides unambiguous information about the degree of ionicity along the group which is linearly correlated with the band gap values and with the cost of forming a single oxygen vacancy. Overall, this study offers a comprehensive insight into the electronic structure of metal oxides and their interrelations. This will help researchers to harness information effectively, boosting the development of novel metal oxide catalysts or innovative methodologies for their preparation. METHODS: Periodic density functional theory was used to predict the atomic structure of the materials of interest. Structure optimization was carried out using the PBE functional, using a plane wave basis set and the PAW representation of the atomic cores, using the VASP code. Next, the electronic properties were computed by carrying out single point calculations employing PBE, PBE + U functionals using VASP and also with PBE and the hybrid HSE06 functionals using the FHI-AIMS software. For the hybrid HSE06, the impact of the screening parameter, ω, and mixing parameter, α, on the calculated band gap has also been assessed.

Anonic Silicon Hydrogels Affect the Concentration of Proteins in Tears during Wear.

PURPOSE: The objective of this study was to quantitatively assess the concentration of human tear proteins in patients wearing contact lenses of various ionicities and determine whether differences were related to the incidence of corneal infiltrative events (CIE). METHODS: 24 subjects (samples) were randomly selected for spectral count analysis to obtain protein concentrations using LCMS analysis. The subjects were neophyte and ametropic with ages between 18 and 40; 6 wore control lenses, 8 wore TestLens1, and 10 wore TestLens2. 16 subjects experienced CIEs during the study. RESULTS: A pairwise multiple hypothesis test identified 7 proteins that significantly differed in concentration between TestLens1 and control, and 11 proteins that differed between TestLens2 and control. Of the 12 unique proteins, 9 were at increased concentration and 3 were at lower concentration in the tears of test lens wearers compared to the control lens group. Bootstrap clustering confirmed these findings, showing 3 similar clusters to the original sample groups which separated people wearing control lenses from those wearing TestLens1 or TestLens2 with 83% accuracy and between TestLens1 and TestLens2 with 45% accuracy. Permutation testing identified 5 proteins that had significantly changed in concentration between people wearing TestLens2 and Control lenses. There was no difference in protein concentrations between those subjects who experienced a CIE and those who did not. CONCLUSION: Wearing contact lenses of different ionicities can affect the concentration of proteins in the tear film. The current study did not find any associations of the concentration of proteins with CIEs. Future tests with increased sample size are needed to establish any relations between these changes and clinical performance.

Energy Electronegativity and Chemical Bonding.

Historical development of the concept of electronegativity (EN) and its significance and prospects for physical and structural chemistry are discussed. The current cutting-edge results are reviewed: new methods of determining the ENs of atoms in solid metals and of bond polarities and effective atomic charges in molecules and crystals. The ENs of nanosized elements are calculated for the first time, enabling us to understand their unusual reactivity, particularly the fixation of N2 by nanodiamond. Bond polarities in fluorides are also determined for the first time, taking into account the peculiarities of the fluorine atom's electronic structure and its electron affinity.

Stable Two-dimensional Nanoconfined Ionic Liquids with Highly Efficient Ionic Conductivity.

Amid the burgeoning environmental concerns, electrochemical energy storage is of great demand, inspiring the rapid development of electrolytes. Quasi-liquid solid electrolytes (QLSEs) demonstrate exciting properties that combine high ionic conductivity and safety. Herein, a QLSE system is constructed by confining ionic liquids (ILs) into 2D materials-based membranes, which creates a subtle platform for the investigation of the nanoconfined ion transport process. The highest ionic conductivity increment of 506% can be observed when ILs are under nanoconfinement. Correlation of experimental results and simulation evidently prove the diffusion behaviors of ILs are remarkably accelerated when confined in nanochannels, ascribing from the promoted dissociation of ILs. Concurrently, nanoconfined ILs demonstrate a highly ordered distribution, lower interplay, and higher free volume compared against bulk systems. This work reveals and analyzes the phenomenon of ionic conductivity elevation in nanoconfined ILs, and offers inspiring opportunities to fabricate the highly stable and efficient QLSEs based on layered nanomaterials for energy storage applications.

Impact of 2D-3D Heterointerface on Remote Epitaxial Interaction through Graphene.

Remote epitaxy has drawn attention as it offers epitaxy of functional materials that can be released from the substrates with atomic precision, thus enabling production and heterointegration of flexible, transferrable, and stackable freestanding single-crystalline membranes. In addition, the remote interaction of atoms and adatoms through two-dimensional (2D) materials in remote epitaxy allows investigation and utilization of electrical/chemical/physical coupling of bulk (3D) materials via 2D materials (3D-2D-3D coupling). Here, we unveil the respective roles and impacts of the substrate material, graphene, substrate-graphene interface, and epitaxial material for electrostatic coupling of these materials, which governs cohesive ordering and can lead to single-crystal epitaxy in the overlying film. We show that simply coating a graphene layer on wafers does not guarantee successful implementation of remote epitaxy, since atomically precise control of the graphene-coated interface is required, and provides key considerations for maximizing the remote electrostatic interaction between the substrate and adatoms. This was enabled by exploring various material systems and processing conditions, and we demonstrate that the rules of remote epitaxy vary significantly depending on the ionicity of material systems as well as the graphene-substrate interface and the epitaxy environment. The general rule of thumb discovered here enables expanding 3D material libraries that can be stacked in freestanding form.

Structure Effects on the Ionicity of Protic Ionic Liquids.

We report on the characterisation of 16 protic ionic liquids (PILs) prepared by neutralisation of primary or tertiary amines with a range of simple carboxylic acids, or salicylic acid. The extent of proton transfer was greater for simple primary amine ILs compared to tertiary amines. For the latter case, proton transfer was increased by providing a better solvation environment for the ions through the addition of a hydroxyl group, either on the tertiary amine, or by formation of PIL/molecular solvent mixtures. The library of PILs was characterised by differential scanning calorimetry and a range of transport properties (i. e. viscosity, conductivity and diffusivity) were measured. Using the (fractional) Walden rule, the conductivity and viscosity results were analysed with respect to their deviation from ideal behaviour. The validity of the Walden plot for PILs containing ions of varying sizes was also verified for a number of samples by directly measuring self-diffusion coefficients using pulsed-field gradient spin-echo (PGSE) NMR. Ionicity was found to decrease as the alkyl chain length and degree of branching of both the cations and anions was increased. These results aim to develop a better understanding of the relationship between PIL properties and structure, to help design ILs with optimal properties for applications.

Interactions and Transport in Highly Concentrated LiTFSI-based Electrolytes.

To elucidate what properties control and practically limit ion transport in highly concentrated electrolytes (HCEs), the viscosity, ionic conductivity, ionicity, and transport numbers were studied for nine model electrolytes and connected to the rate capability in Li-ion battery (LIB) cells. The electrolytes employed the LiTFSI salt in three molar ratio concentrations; 1 : 2, 1 : 4, and 1 : 16 (LiTFSI:X) vs. solvents (X) with different permittivities; tert-butyl methyl ether (MTBE), tetrahydrofuran (THF) and propylene carbonate (PC). While the low polarity MTBE creates liquid electrolytes, ion-pairing limits the ionic conductivity despite extremely low viscosities. For the less concentrated 1 : 16 LiTFSI:MTBE and 1 : 16 LiTFSI:THF electrolytes the ionic diffusivities decrease with increased temperature, a sign of aggregation, but still their ionic conductivities and LIB performance increase. In general, the low ionic conductivity and high viscosity both limit the use of HCEs in LIBs, and no compensating mechanism seems to be present.

The Atomic Partial Charges Arboretum: Trying to See the Forest for the Trees.

Atomic partial charges are among the most commonly used interpretive tools in quantum chemistry. Dozens of different 'population analyses' are in use, which are best seen as proxies (indirect gauges) rather than measurements of a 'general ionicity'. For the GMTKN55 benchmark of nearly 2,500 main-group molecules, which span a broad swathe of chemical space, some two dozen different charge distributions were evaluated at the PBE0 level near the 1-particle basis set limit. The correlation matrix between the different charge distributions exhibits a block structure; blocking is, broadly speaking, by charge distribution class. A principal component analysis on the entire dataset suggests that nearly all variation can be accounted for by just two 'principal components of ionicity': one has all the distributions going in sync, while the second corresponds mainly to Bader QTAIM vs. all others. A weaker third component corresponds to electrostatic charge models in opposition to the orbital-based ones. The single charge distributions that have the greatest statistical similarity to the first principal component are iterated Hirshfeld (Hirshfeld-I) and a minimal-basis projected modification of Bickelhaupt charges. If three individual variables, rather than three principal components, are to be identified that contain most of the information in the whole dataset, one representative for each of the three classes of Corminboeuf et al. is needed: one based on partitioning of the density (such as QTAIM), a second based on orbital partitioning (such as NPA), and a third based on the molecular electrostatic potential (such as HLY or CHELPG).

Impacts of hydrophobicity and ionicity of phendione-based cobalt(II)/(III) complexes on binding with bovine serum albumin.

For efficient designing of metallodrugs, it is imperative to analyse the binding affinity of those drugs with drug-carrying serum albumins to comprehend their structure-activity correlation for biomedical applications. Here, cobalt(II) and cobalt(III) complexes comprising three phendione ligands, [Co(phendione)3]Cl2 (1) and [Co(phendione)3]Cl3 (2), where, phendione = 1,10-phenanthroline-5,6-dione, has been chosen to contrast the impact of their hydrophobicity and ionicity on binding with bovine serum albumin (BSA) through spectrophotometric titrations. The attained hydrophobicity values using octanol/water partition coefficient method manifested that complex 1 is more hydrophobic than complex 2, which could be attributed to lesser charge on its coordination sphere. The interaction of complexes 1 and 2 with BSA using steady state fluorescence studies revealed that these complexes quench the intrinsic fluorescence of BSA through static mechanism, and the extent of quenching and binding parameters are higher for complex 2. Further thermodynamics of BSA-binding studies revealed that complexes 1 and 2 interact with BSA through hydrophobic and hydrogen bonding/van der Waals interactions, respectively. Further, UV-visible absorption, circular dichroism and synchronous fluorescence studies confirmed the occurrence of conformational and microenvironmental changes in BSA upon binding with complexes 1 and 2. Molecular docking studies have also shown that complex 2 has a higher binding affinity towards BSA as compared to complex 1. This sort of modification of ionicity and hydrophobicity of metal complexes for getting desirable binding mode/strength with drug transporting serum albumins will be a promising pathway for designing active and new kind of metallodrugs for various biomedical applications.Communicated by Ramaswamy H. Sarma.

Achieving band convergence by tuning the bonding ionicity in n-type Mg3 Sb2.

Identifying strategies for beneficial band engineering is crucial for the optimization of thermoelectric (TE) materials. In this study, we demonstrate the beneficial effects of ionic dopants on n-type Mg3 Sb2 . Using the band-resolved projected crystal orbital Hamilton population, the covalent characters of the bonding between Mg atoms at different sites are observed. By partially substituting the Mg at the octahedral sites with more ionic dopants, such as Ca and Yb, the conduction band minimum (CBM) of Mg3 Sb2 is altered to be more anisotropic with an enhanced band degeneracy of 7. The CBM density of states of doped Mg3 Sb2 with these dopants is significantly enlarged by band engineering. The improved Seebeck coefficients and power factors, together with the reduced lattice thermal conductivities, imply that the partial introduction of more ionic dopants in Mg3 Sb2 is a general solution for its n-type TE performance. © 2019 Wiley Periodicals, Inc.

Concentration Dependence of Ion Pairing in Imidazolium-Based Ionic Liquid Solutions.

Infrared vibrational spectroscopy was used to probe concentration-dependent ion pair dissociation of imidazolium-based ionic liquids with three different halide anions (I- , Br- , and Cl- ) in deuterated chloroform. Dissociation of the ion pairs at low concentrations of ionic liquids was found to be the easiest for ionic liquid with Cl- anion, the most electronegative anion among the three investigated. This anomalous trend of ion pair dissociation was explained in terms of varying interaction strength between the solvent (CDCl3 ) and the anions investigated.

Multiple Ether-Functionalized Phosphonium Ionic Liquids as Highly Fluid Electrolytes.

Ionic liquids (ILs) are promising electrolytes, although their often high viscosity remains a serious drawback. The latter can be addressed by the introduction of multiple ether functionalization. Based on the highly atom efficient synthesis of tris(2-ethoxyethyl) phosphine, several new phosphonium ionic liquids were prepared, which allows studying the influence of the ether side chains. Their most important physicochemical properties have been determined and will be interpreted using established approaches like ionicity, hole theory, and the Walden plot. There is striking evidence that the properties of phosphonium ionic liquids with the methanesulfonate anion are dominated by aggregation, whereas the two triple ether functionalized ILs with the highest fluidity show almost ideal behavior with other factors being dominant. It is furthermore found that the deviation from ideality is not significantly changed upon introduction of the ether side chains, although a very beneficial impact on the fluidity of ILs is observed. Multiple ether functionalization therefore proves as a powerful tool to overcome the disadvantages of phosphonium ionic liquids with large cations.

Ion Transport Properties and Ionicity of 1,3-Dimethyl-1,2,3-Triazolium Salts with Fluorinated Anions.

1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from ¹H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices.

Bond orders for intermolecular interactions in crystals: charge transfer, ionicity and the effect on intramolecular bonds.

The question of whether intermolecular interactions in crystals originate from localized atom⋯atom interactions or as a result of holistic molecule⋯molecule close packing is a matter of continuing debate. In this context, the newly introduced Roby-Gould bond indices are reported for intermolecular 'σ-hole' interactions, such as halogen bonding and chalcogen bonding, and compared with those for hydrogen bonds. A series of 97 crystal systems exhibiting these interaction motifs obtained from the Cambridge Structural Database (CSD) has been analysed. In contrast with conventional bond-order estimations, the new method separately estimates the ionic and covalent bond indices for atom⋯atom and molecule⋯molecule bond orders, which shed light on the nature of these interactions. A consistent trend in charge transfer from halogen/chalcogen bond-acceptor to bond-donor groups has been found in these intermolecular interaction regions via Hirshfeld atomic partitioning of the electron populations. These results, along with the 'conservation of bond orders' tested in the interaction regions, establish the significant role of localized atom⋯atom interactions in the formation of these intermolecular binding motifs.

Covalency and Ionicity Do Not Oppose Each Other-Relationship Between Si-O Bond Character and Basicity of Siloxanes.

Covalency and ionicity are orthogonal rather than antipodal concepts. We demonstrate for the case of siloxane systems [R3 Si-(O-SiR2 )n -O-SiR3 ] that both covalency and ionicity of the Si-O bonds impact on the basicity of the Si-O-Si linkage. The relationship between the siloxane basicity and the Si-O bond character has been under debate since previous studies have presented conflicting explanations. It has been shown with natural bond orbital methods that increased hyperconjugative interactions of LP(O)→σ*(Si-R) type, that is, increased orbital overlap and hence covalency, are responsible for the low siloxane basicity at large Si-O-Si angles. On the other hand, increased ionicity towards larger Si-O-Si angles has been revealed with real-space bonding indicators. To resolve this ostensible contradiction, we perform a complementary bonding analysis, which combines orbital-space, real-space, and bond-index considerations. We analyze the isolated disiloxane molecule H3 SiOSiH3 with varying Si-O-Si angles, and n-membered cyclic siloxane systems Si2 H4 O(CH2 )n-3 . All methods from quite different realms show that both covalent and ionic interactions increase simultaneously towards larger Si-O-Si angles. In addition, we present highly accurate absolute hydrogen-bond interaction energies of the investigated siloxane molecules with water and silanol as donors. It is found that intermolecular hydrogen bonding is significant at small Si-O-Si angles and weakens as the Si-O-Si angle increases until no stable hydrogen-bond complexes are obtained beyond φSiOSi =168°, angles typically displayed by minerals or polymers. The maximum hydrogen-bond interaction energy, which is obtained at an angle of 105°, is 11.05 kJ mol-1 for the siloxane-water complex and 18.40 kJ mol-1 for the siloxane-silanol complex.

Preparation, Characterization, and Formulation Development of Drug-Drug Protic Ionic Liquids of Diphenhydramine with Ibuprofen and Naproxen.

Diphenhydramine (DPH) has been used with ibuprofen (IBU) or naproxen (NAP) in combined therapies to provide better clinical efficacy as an analgesic and sleep aid. We discovered that DPH can form protic ionic liquids (PILs) with IBU and NAP, which opens the opportunity for a new delivery mode of these combination drugs. [DPH][IBU] and [DPH][NAP] PILs exhibit low ionicity, as confirmed by Fourier transform infrared and 1H NMR spectroscopy, and accompanied by low diffusivity, high viscosity, and poor ionic conductivity. Evaluation of pharmaceutical properties of the two PILs showed that these PILs, despite high solubility and good wettability, exhibited low dissolution rates, owing to the poor dispersion of the PIL drops and the resultant small surface area during dissolution. However, when loaded into a mesoporous carrier, the PIL-carrier composites exhibited improved dissolution rates along with excellent flow properties and easy handling. Oral capsules of both PILs were developed using such composites. Such capsule products exhibited acceptable drug release and bioavailability as demonstrated by a predictive artificial stomach-duodenum dissolution test.

Automated first-principles mapping for phase-change materials.

Plotting materials on bi-coordinate maps according to physically meaningful descriptors has a successful tradition in computational solid-state science spanning more than four decades. Equipped with new ab initio techniques introduced in this work, we generate an improved version of the treasure map for phase-change materials (PCMs) as introduced previously by Lencer et al. which, other than before, charts all industrially used PCMs correctly. Furthermore, we suggest seven new PCM candidates, namely SiSb4 Te7 , Si2 Sb2 Te5 , SiAs2 Te4 , PbAs2 Te4 , SiSb2 Te4 , Sn2 As2 Te5 , and PbAs4 Te7 , to be used as synthetic targets. To realize aforementioned maps based on orbital mixing (or "hybridization") and ionicity coordinates, structural information was first included into an ab initio numerical descriptor for sp3 orbital mixing and then generalized beyond high-symmetry structures. In addition, a simple, yet powerful quantum-mechanical ionization measure also including structural information was introduced. Taken together, these tools allow for (automatically) generating materials maps solely relying on first-principles calculations. © 2017 Wiley Periodicals, Inc.

High Coulombic efficiency aluminum-ion battery using an AlCl3-urea ionic liquid analog electrolyte.

In recent years, impressive advances in harvesting renewable energy have led to a pressing demand for the complimentary energy storage technology. Here, a high Coulombic efficiency (∼99.7%) Al battery is developed using earth-abundant aluminum as the anode, graphite as the cathode, and a cheap ionic liquid analog electrolyte made from a mixture of AlCl3 and urea in a 1.3:1 molar ratio. The battery displays discharge voltage plateaus around 1.9 and 1.5 V (average discharge = 1.73 V) and yielded a specific cathode capacity of ∼73 mAh g-1 at a current density of 100 mA g-1 (∼1.4 C). High Coulombic efficiency over a range of charge-discharge rates and stability over ∼150-200 cycles was easily demonstrated. In situ Raman spectroscopy clearly showed chloroaluminate anion intercalation/deintercalation of graphite (positive electrode) during charge-discharge and suggested the formation of a stage 2 graphite intercalation compound when fully charged. Raman spectroscopy and NMR suggested the existence of AlCl4-, Al2Cl7- anions and [AlCl2·(urea)n]+ cations in the AlCl3/urea electrolyte when an excess of AlCl3 was present. Aluminum deposition therefore proceeded through two pathways, one involving Al2Cl7- anions and the other involving [AlCl2·(urea)n]+ cations. This battery is a promising prospect for a future high-performance, low-cost energy storage device.

Kamlet-Taft Solvation Parameters of Solvate Ionic Liquids.

The Kamlet-Taft solvent parameters of solvate ionic liquids (SILs) prepared from lithium salts with glyme and glycol ligands are determined. The dipolarity/polarisibilities (π*) are high, similar to those found in conventional ionic liquids. The H-bond basicities (ß) depend strongly on the anion. The H-bond acidities (α) are high in both glyme and glycol SILs, indicating that the lithium is acting as a H-bond donor site. "Poor" SILs have glyme-rich and salt-rich regions. In these liquids the π* and ß values are almost identical to the parent glyme or glycol, and the α values are determined by the salt alone.