Local Chemical Descriptors Research Articles

Structural, electronic, and thermal studies of Poly(ethylene oxide) based solid-state polymer electrolyte

Abstract All-solid-state polymer electrolytes have grown in significance for next-generation energy storage devices because of their high energy endurance, safety, and flexibility. Electrolytes made of poly(ethylene oxide) (PEO) have received a lot of interest because they can dissolve a wide range of ionic salts. We have observed the effects of lithium bis(trifluoromethanesulfonyl)imide salts on the structural, electronic, and thermal properties of solid-state polymer electrolyte systems incorporating PEO using methods based on density functional theory. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) i.e., HOMO-LUMO gap of the PEO and polymer electrolyte are found at 5.74 eV and 3.84 eV, respectively. The value of the HOMO-LUMO gap for PEO and solid-state polymer electrolyte shows similarity with the previous studies. The global and local chemical descriptors are calculated using the HOMO-LUMO gap. The electrochemical stability analysis is performed using the HOMO-LUMO method. Thermal functions also have been studied using density functional theory techniques. The theoretical vibrational frequencies of PEO and solid-state polymer electrolyte are investigated and compared with experimental values.

The effect of nitrogen-rich ionic liquid [EMIMDCA] on the electronic structure of solid polymer electrolyte (PEO-LiTFSI).

In our work, the ab-initio methods based on density functional theory (DFT) formalism are used to investigate the effect of nitrogen-rich ionic liquid (EMIMDCA; 1-ethyl-3-methylimidazolium dicyanamide) on the electronic structure of SPE (solid polymer electrolyte) (PEO-LiTFSI) electrolyte with B3LYP method and LANL2DZ basis set. The differences in energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), i.e., energy gap ([Formula: see text]) of the PEO, [EMIMDCA], SPE, and ionogel (IG), are found 5.74, 6.59, 3.25, and 2.80eV, respectively. In SPE, the reduced band gap ([Formula: see text]) is due to the transportation of cation of LiTFSI (Li+ ion). Finally, the reduced band gap of IG confirms that IL enhances the transportation of cation of LiTFSI (Li+ ion) through the oxygen atom of PEO. The global and local chemical descriptors and electrochemical stability windows (ESWs) are calculated using the HOMO-LUMO energy levels. Partial charge analysis is studied by Mulliken population analysis and molecular electrostatic potential surface.

Synthesis, crystal structure, antibacterial, antiproliferative and QSAR studies of new bismuth(III) complexes of pyrrolidineditiocarbamate of dithia-bismolane and bismane, oxodithia- and trithia-bismocane

Four new bismuth(III) complexes; (CH2S)2Bi[S2CN(CH2)4] (2), CH2(CH2S)2Bi[S2CN(CH2)4] (3), S(CH2CH2S)2Bi[S2CN(CH2)4] (4), O(CH2CH2S)2Bi[S2CN(CH2)4] (5) were prepared from the reaction of the sodium salt of pyrrolidine-dithiocarbamate (1) with four chloro-dithia-bismuth(III) compounds containing five-, six- and eight-membered heterocycles. The complexes were characterized by elemental analyses, infrared, and 1H and 13C NMR spectroscopy. In addition, the single crystal X-ray structures of 2–4 were obtained, showing an asymmetric bidentate coordination mode of the dithiocarbamate ligand moiety. The metal center in 2 and 3 is tetracoordinated, while in 4 a pentacoordinate metal center is observed, the latter is achieved through the 1,5-transannular Bi⋯S interaction, which is common in these types of metallocane rings. Antibacterial assays showed that 2–5 were active in ATCC and clinical isolated strains. Antiploliferation assays were carried out showing high antiproliferative effect against breast cancer cell lines, in vitro. A QSAR model employing quantum global and local chemical descriptors was constructed to gain further insight into their antibacterial activity.

Role of Reaction Conditions in the Global and Local Two Parabolas Charge Transfer Model.

The local and global charge transfer approach based on the two parabolas model is applied to several problems aiming to show the importance of incorporating the reaction conditions to evaluate the global and local chemical descriptors. It is shown that, by preparation of the reactants, the chemical potentials of the reacting species determined by the two parabolas model satisfy the condition for the transfer of electrons in the direction dictated by the chemical potential difference. The model is applied to the hydration of alkenes, showing that it recovers Markovnikov's rule, to aromatic nitration, and to the interaction of nitrobenzenes with 1,3-diethylurea, an electrochemically controlled hydrogen-bonding problem. The applications presented show that to satisfy the charge transfer directionality established by the chemical potential differences obtained from the two parabolas model, one has to incorporate the reaction conditions in the evaluation of the global and local chemical descriptors. The global and local charge transfer predicted along these lines allows one to determine the direction of electron transfer prevailing in the reaction and also the most relevant atoms participating in the interactions between the reactants, aiding in the unraveling of the chemical interactions present in the system under investigation.

Understanding selectivity of hard and soft metal cations within biological systems using the subvalence concept. I. Application to blood coagulation: direct cation-protein electronic effects vs. indirect interactions through water networks.

Following a previous study by de Courcy et al. ((2009) Interdiscip. Sci. Comput. Life Sci. 1, 55-60), we demonstrate in this contribution, using quantum chemistry, that metal cations exhibit a specific topological signature in the electron localization of their density interacting with ligands according to its "soft" or "hard" character. Introducing the concept of metal cation subvalence, we show that a metal cation can split its outer-shell density (the so-called subvalent domains or basins) according to it capability to form a partly covalent bond involving charge transfer. Such behaviour is investigated by means of several quantum chemical interpretative methods encompasing the topological analysis of the Electron Localization Function (ELF) and Bader's Quantum Theory of Atoms in Molecules (QTAIM) and two energy decomposition analyses (EDA), namely the Restricted Variational Space (RVS) and Constrained Space Orbital Variations (CSOV) approaches. Further rationalization is performed by computing ELF and QTAIM local properties such as electrostatic distributed moments and local chemical descriptors such as condensed Fukui Functions and dual descriptors. These reactivity indexes are computed within the ELF topological analysis in addition to QTAIM offering access to non atomic reactivity local index, for example on lone pairs. We apply this "subvalence" concept to study the cation selectivity in enzymes involved in blood coagulation (GLA domains of three coagulation factors). We show that the calcium ions are clearly able to form partially covalent charge transfer networks between the subdomain of the metal ion and the carboxylate oxygen lone pairs whereas magnesium does not have such ability. Our analysis also explains the different role of two groups (high affinity and low affinity cation binding sites) present in GLA domains. If the presence of Ca(II) is mandatory in the central "high affinity" region to conserve a proper folding and a charge transfer network, external sites are better stabilised by Mg(II), rather than Ca(II), in agreement with experiment. The central role of discrete water molecules is also discussed in order to understand the stabilities of the observed X-rays structures of the Gla domain. Indeed, the presence of explicit water molecules generating indirect cation-protein interactions through water networks is shown to be able to reverse the observed electronic selectivity occuring when cations directly interact with the Gla domain without the need of water.