Interaction Of Solvent Molecules Research Articles

Ionomer solution to film solidification dependence upon solvent type and its impact upon morphology and ion transport

Ionomer chain and solvent molecule interactions during solution-casting, solvent evaporation, and solidification impacts chain entanglements, spatial arrangement of functional groups, microstructure development, morphology, and physical properties. These concepts were investigated using poly(t-butylstyrene-b-ethylene-alt-propylene-b-sulfonatedstyrene-b-ethylene-alt-propylene-b-t-butylstyrene) with a fixed ion-exchange capacity of 1.0, and estimated solubility parameter of 21.8 (J/cm3)1/2. Films were solution-cast using an equal volume cyclohexane:heptane mixture (C:H), chloroform (CHCl3), and tetrahydrofuran (THF). Subsequent film structures were evaluated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), FT-IR, and electrochemical impedance spectroscopy. A commercially supplied film had sulfonated domains randomly distributed throughout it, and its initial proton conductivity was 11.8mS/cm. A film created by solution-casting from C:H had a morphology containing randomly distributed sulfonated domains. This random morphology became more ordered with a lamella-like morphology when solution-cast using THF. The film produced from CHCl3 had a morphology that was between random and ordered. Film morphology differences were attributed to a poorer solvent system that inhibited chain solvation. The solution-cast film’s proton conductivity was 1.0mS/cm for a random morphology, and 15.3mS/cm with a lamella-like structure. Increasing the ionomer-THF solution-casting temperature to 40°C produced a film with a 103% increase in conductivity (31.2mS/cm). This led to a water uptake change from 29wt% to 80wt%. Cycling a THF solution-cast film from its dry to a wet state revealed that a lamella-like morphology would maintain its conductivity, but the commercial film’s conductivity decreased from 11.8mS/cm to 0.98mS/cm. Ionomer film properties were found to be dependent upon solvent quality and processing.

The Role of Structure Making/Breaking Ions in Solvation Shell and Redox Reaction Entropy of Outer Sphere Electron Transfer Reactions

Marcus theory1 of electron transfer is the dominant theory to describe the rate constant of electron transfer reactions both in chemistry and biology during last several decades. The general treatment on the solvation free energy of reactants is largely based on Born model2 that the solvent is assumed as a dielectric continuum and each reactant is treated as a sphere where the first solvation layer is dielectrically saturated. However, these assumptions could shield the fact of non-covalent interactions within the solvation shell of reactants, including reactant nuclei-solvent, reactant nuclei-inert ion, inert ion-solvent interactions and hydrogen bonding of solvent molecules. The entropy change of an electron transfer reactions, , is the difference of standard molar entropy between the reduced and oxidized forms of a redox couple. The reaction entropy of outer sphere self-exchange can be qualitatively described by Born model even though the Born prediction differs from the experimental data of some redox couples, according to previous studies3. It was shown that the reaction entropy of a given redox couple increases with decreasing in solvent acceptor number. This dependence of upon the solvent nature could be associated with the degree of “internal order” of solvent molecules. Besides solvent-solvent molecule interaction, the “internal order” of solvent could be disrupted by dissolved charged species, including the reactant nuclei of redox couples and inert ions either from the counter-ion of redox couples or from the supporting electrolyte. Depending on its effects on water structure and vice versa, ions are usually categorized in either “structure maker” or “structure breaker”4, which could affect surrounding hydrogen bonds and water molecular arrangement around itself5. In addition to solvent-solvent and ion-solvent interactions, the coulombic interaction between the redox couples and the ions with opposite sign of charge to those of redox couples has been suggested6. It could form an ionic atmosphere and, thereby affects to the reaction entropy of redox couples. In aqueous electrolyte, a simple description of this coulombic interaction by an electrostatic energy necessary for forming an ionic atmosphere by surrounding the species with the counter ions seems not to be prudent due to the fact of ternary interactions of redox nuclei, counter ions and solvent molecules. However, the non-covalent interactions have not, to the best of our knowledge, previously been considered in terms of the entropy change of outer sphere self-exchange electron transfer reactions, and it is the impact of structure making/breaking ions on the structure of the solvation shell of the reactant nuclei that constitutes the focus of this work. Here, we studied reaction entropy of two outer sphere reactions: [Fe(H2O)6]2+/3+ and [Fe(CN)6]3-/4- upon the nature and the concentration of anions and cations, respectively. For both positively and negatively charged redox couples, it was shown that structure maker ions enhance the “order” in vicinity of redox nuclei while structure breaker ions promote “disorder”. We suggest also molecular level models for redox nuclei solvation by taking into account reactant nuclei-solvent, reactant nuclei-inert ion, inert ion-solvent interactions and hydrogen bonding of solvent molecules. References (1) Marcus, R. A. J. Chem. Phys. 1956, 24, 966. (2) Born, M. Z. Für Phys. 1920, 1 (1), 45–48. (3) Hupp, J. T.; Weaver, M. J. Inorg. Chem. 1984, 23 (22), 3639–3644. (4) Marcus, Y. Chem. Rev. 2009, 109 (3), 1346–1370. (5) Miller, D. J.; Lisy, J. M. J. Am. Chem. Soc. 2008, 130 (46), 15381–15392. (6) Yamato, Y.; Katayama, Y.; Miura, T. J. Electrochem. Soc. 2013, 160 (6), H309–H314.

The Effect of Li Ion Dissociation Level in Gel Polymer Electrolytes on Electrochemical Performance of Li-O2 Batteries

Li-O2 batteries have been recently considered as next generation of energy storage systems for electric vehicle application due to their high specific energy densities, which are comparable to gasoline [1]. Li-O2 batteries however suffer poor cycling and reachability due to a sever electrolyte decomposition [2]. It has been shown that the electrolyte decomposition by-products such as lithium carbonate species gradually cover the surface of cathodes and shuts down the batteries quickly [3]. Although many attempts have been made to overcome the detrimental formation of these carbonate species on the surface of cathode, their formation and electrolyte instability still remains a very big challenge in this filed [4]. Recently, it has been reported that tailoring the coordination of Li ion and solvent molecules in Li-O2 battery electrolytes is a promising method to improve the electrolyte stabilities [5,6]. In this study, we report that the inclusion of inorganic fillers in gel polymer electrolytes using different salt concentration can reduce the electrolyte decomposition by-products such as lithium carbonate species during the Li-O2 battery cycling. The improved electrochemical performance of Li-O2 batteries can be attributed to the interaction of filler with Li salt which in turn can tailor the interaction of Li ion and solvent molecules. To asses our hypothesis different electrochemical tests including in-depth electrochemical impedance spectroscopy, lithium transference number measurements along with other characterization methods such as Raman spectroscopy has been used. [1] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, W. Wilcke, Lithium-air battery: Promise and challenges, J. Phys. Chem. Lett. 2010,1, 2193–2203. [2] B. D. McCloskey, C. M. Burke, J. E. Nichols and S. E. Renfrew, Chem. Commun., 2015, 51, 12701–12715 [3] S. A. Freunberger, Y. Chen, N. E. Drewett, L. J. Hardwick, F. Bardé and P. G. Bruce, Angew. Chemie - Int. Ed., 2011, 50, 8609–8613 [4] R. Younesi, G.M. Veith, P. Johansson, K. Edstrom, T. Vegge, Lithium salts for advanced lithium batteries: Li-metal, Li-O2, and Li-S, Energy Environ. Sci.,2015, 8, 1905–1922. [5] F. Li, T. Zhang, Y. Yamada, A. Yamada and H. Zhou, Adv. Energy Mater., 2013, 3, 532–538. [6] B. Liu, W. Xu, P. Yan, X. Sun, M. E. Bowden, J. Read, J. Qian, D. Mei, C. M. Wang and J. G. Zhang, Adv. Funct. Mater., 2016, 26, 605–613.

Competitive solvent-molecule interactions govern primary processes of diphenylcarbene in solvent mixtures.

Photochemical reactions in solution often proceed via competing reaction pathways comprising intermediates that capture a solvent molecule. A disclosure of the underlying reaction mechanisms is challenging due to the rapid nature of these processes and the intricate identification of how many solvent molecules are involved. Here combining broadband femtosecond transient absorption and quantum mechanics/molecular mechanics simulations, we show for one of the most reactive species, diphenylcarbene, that the decision-maker is not the nearest solvent molecule but its neighbour. The hydrogen bonding dynamics determine which reaction channels are accessible in binary solvent mixtures at room temperature. In-depth analysis of the amount of nascent intermediates corroborates the importance of a hydrogen-bonded complex with a protic solvent molecule, in striking analogy to complexes found at cryogenic temperatures. Our results show that adjacent solvent molecules take the role of key abettors rather than bystanders for the fate of the reactive intermediate.

Complexation and Phase Evolution at Dimethylformamide–Ag(111) Interfaces

The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF)2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV–STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF)2, through the saturation monolayer limit, in which these two chemical species phase separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF)2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure–composition phase diagram, which allows structure prediction over arbitrary experimental conditions. This work reveals new surface coordination chemistry for an important electrolyte–electrode system and illustrates how surface pressure can be used to tune monolayer phases.

Acoustical Investigation of N–(2-hydroxybenzylidene)-3-Substituted Pyridine -2- Amine Schiff bases by Ultrasonic Velocity Measurements in Dioxane at Different Temperatures

<div><p><em>The present work deals with the study of acoustic parameters like ultrasonic velocity (V), </em><em>adiabatic compressibility (β<sub>s</sub>), apparent molar volume (</em><em>f</em><em><sub>v</sub></em><em>) and intermolecular free length (L<sub>f</sub>) by ultrasonic </em><em>interferometric measurements</em><em> which reflects structural interaction of water molecules and organic solvent molecules with substituted Schiff bases. The study of N–(2-hydroxybenzylidene)-3-substituted pyridine -2- amine Schiff bases were carried in different percentage of 1,4-dioxane-water medium, at 293, 297 and 300 K. The densities and velocities thus obtained were used to evaluate acoustic parameters for all the ligands.</em></p></div>

Solvation of coumarin6 studied by vibrational spectroscopy and density functional theory

Effect of solvation on coumarin6 dye has been studied with density functional theory (DFT). Optimized structure of the dye has been obtained in various solvents and frequencies of various vibrational bands have been calculated in these solvents. Calculations predict shift in the frequency of certain bands in the solvents. Similar shifts have been observed experimentally in the vibrational spectra of the dye in solvents. In order to ascertain the origin of these shifts, the interactions of solvent molecules with the coumarin6 molecule have been studied using various tools of DFT like donor-acceptor interactions, Molecular Electrostatic potential (MEP) and HOMO-LUMO analysis etc.

Unfolding of Hydrated Alkyl Diammonium Cations Revealed by Cryogenic Ion Mobility-Mass Spectrometry.

Hydration of the ammonium ion plays a key role in determining the biomolecular structure as well as local structure of water in aqueous environments. Experimental data obtained by cryogenic ion mobility-mass spectrometry (cryo-IM-MS) show that dehydration of alkyl diammonium cations induces a distinct unfolding transition at a critical number of water molecules, n = 21 to 23, n = 24 to 26, and n = 27 to 29, for 1,7-diaminoheptane, 1,8-diaminooctane, and 1,10-diaminodecane, respectively. Results are also presented that reveal compelling evidence for unique structural transitions of hydrated ammonium ions associated with the development of the hydrogen-bond network around individual charged groups. The ability to track the evolution of structure upon stepwise dehydration provides direct insight into the intricate interplay between solvent-molecule interactions that are responsible for defining conformations. Such insights are potentially valuable in understanding how ammonium ion solvation influences conformation(s) of larger biomolecules.

Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Non-Aqueous Electrolytes

Rechargeable Mg batteries have been identified as a candidate storage system for the next-generation high energy density rechargeable batteries because of the possibility of pairing a non-dendrite forming Mg metal anode (~2.37 V vs. SHE) with high theoretical specific capacity (2205 A h kg-1) [1] with a Mg intercalation-based cathode. However, several daunting problems still prevent the realization of Mg-battery: (i) the limited selectivity of electrolyte systems that display reversible Mg deposition, (ii) the narrow electrochemical window of the electrolyte, (iii) lack of high-voltage cathode materials, (iv) irremediable interruption of the battery functions by passivation of the anode material. While it is well established that Mg can be deposited reversibly from complex ethereal solutions of Mg-Chloro complex reagents, the stripping/deposition mechanism at the anode is still debated [2,3]. In this talk we present a detailed atomistic DFT study of the interaction of solvent molecules i.e. THF, and the salts (Mg-Chloro complex) when in contact with Mg-anode surfaces, focusing on the competitive absorption of these chemical species at the interface [4]. Ab initiomolecular dynamics results will complement adsorption calculations providing a better understanding of the morphology of the electrolyte/anode interface. These models are essential to clarify the challenging electron-transfer mechanism occurring at the electrode/solvent interface [4].

Evidence of carbon nanoparticle–solvent molecule interactions in Raman and fluorescence spectra

Interactions of oxidized detonation nanodiamond and carbon dots with protic solvent molecules in suspensions of water, methanol, and isopropyl alcohol were studied by Raman and fluorescence spectroscopy. The structure of the solvent at the interface with nanoparticles and the strength of the hydrogen bonds between the functional groups on the surface of the nanoparticles and the solvent molecules depend on the type of solvent. The molecules of the solvent affect the fluorescent properties of the nanoparticles. It was found that the more intense fluorescence of nanoparticles corresponds to weaker hydrogen bonding between the surface of the carbon nanoparticles and the surrounding molecules of the solvent. The mechanism of mutual influence of the carbon nanoparticles and the solvent on the properties of each other has been suggested.Fluorescence properties of nanodiamonds in the solvents with different hydrogen bonding.

Spectral, Electrochemical and Molecular Orbital Studies on a New Solvatochromic Binuclear Mixed Ligand Copper(II) Complexes

A new series of solvatochromic binuclear mixed ligand complexes with the general formula: Cu2(DMCHD)(Am)2X3 (where, DMCHD: 5.5-Dimethyl cyclohexanate 1,3-dione, Am=N,N,N’-trimethylethylenediamine (Me3en), N,N,N’,N’- tetramethylethylenediamine (Me4en), or N,N,N’,N’,N’’-penta-methyldiethylenetriamine (Me5dien) and X=ClO4- or Clhave been synthesized and characterized by the analytical, spectral methods, magnetic and molar conductance as well as electrochemical measurements. The formation constant values for HDMCHD ligand with various metal ions are much lower than expected for similar β-diketones revealing a monobasic unidentate nature of this ligand. The d-d absorption bands of the prepared complexes in weak donor solvents suggest square-planar, distorted octahedral and/ or distorted trigonal bipyramid geometries for the perchlorate and chloride of diamine in addition to triamine complexes, respectively. However, an octahedral structure was identified for the complexes in strong donor solvents. Perchlorate of diamine complexes show a remarkable color change from violet to green as the Lewis basicity of the donor solvent or anions increases, whereas chloride complex is mainly affected by the Lewis acidity of the acceptor solvent. Specific and non-specific interactions of solvent molecules with the complexes have been investigated using the unified solvation model. Band’s oscillator strength of the d-d transition has been calculated and discussed. Cyclic voltammetric measurements on the prepared complexes in different solvents showed a quasi-reversible or irreversible and mainly diffusion controlled reduction process. Such behavior has been explained according to the EECE mechanism. A linear correlation has been found between the Cu(II) reduction potential and the spectral data. Structural parameters of the free ligands and their Cu(II)- complexes have been calculated on the basis of semiemperical PM3 level and correlated with the experimental data.

Reactivity and molecular modeling of new solvatochromic mixed-ligand copper(II) chelates of 2-acetylbutyrolactone and dinitrogen bases

A new series of solvatochromic mononuclear mixed ligand chelates with the general formula: Cu(AcBL)(L)X; where AcBL=2-acetylbutyrolactonate, L=N,N,N′,N′-tetramethylethylenediamine (Me4en), N,N,N′,N′-tetramethylpropylene diamine (Me4pn), 1,10-phenanthroline (Phen) or 2,2′-bipyridyl (Bipy) and X=ClO4−, NO3− or Br− have been synthesized and characterized by the analytical and spectral methods, as well as magnetic and molar conductance measurements. The d–d absorption bands of Me4en-chelates as Nujol mulls or weak donor solvents solutions revealed square-planar, distorted octahedral and/or distorted trigonal bipyramid geometries for the perchlorate, nitrate and bromide chelates, respectively. However, an octahedral structure is identified for chelates in strong donor solvents. Perchlorate chelates show a remarkable color change from violet to green as the Lewis basicity of the donor solvent increases, whereas bromide chelates are mainly affected by the Lewis acidity of solvent. Specific and non-specific interactions of solvent molecules with the chelates were investigated on the basis of unified solvation model. Structural parameters of the free ligands and their Cu(II)-chelates have been calculated on the basis of semiempirical PM3 level and correlated with the experimental data.

Stability optimisation of molecular electronic devices based on nanoelectrode–nanoparticle bridge platform in air and different storage liquids

The long-term stability of metal nanoparticle–molecule junctions in molecular electronic devices based on nanoelectrodes (NEL) is a major challenge in the effort to bring related molecular electronic devices to application. To optimize the reproducibility of molecular electronic nanodevices, the time-dependent modification of such junctions as exposed to different media needs to be known. Here, we have studied (1) the stability of Au-NEL and (2) the electrical stability of molecule–Au nanoparticle (AuNP) junctions themselves with the molecule being 1,8-octanedithiol (ODT). Both the NELs only and the junctions were exposed to air and liquids such as deionized water, tetrahydrofuran, toluene and tetramethylethylenediamine (TMEDA) over a period of 1 month. The nanogaps remained stable in width when stored in either deionized water or toluene, whereas the current through 1,8-octanedithiol–NP junctions remained most stable when stored in TMEDA as compared to other solvents. Although it is difficult to follow the chemical processes in such devices in the 10-nm range with analytical methods, the behavior can be interpreted from known interactions of solvent molecules with electrodes and ODT.

Effect of cosolvent on protein stability: a theoretical investigation.

We developed a statistical thermodynamic algorithm for analyzing solvent-induced folding/unfolding transitions of proteins. The energetics of protein transitions is governed by the interplay between the cavity formation contribution and the term reflecting direct solute-cosolvent interactions. The latter is viewed as an exchange reaction in which the binding of a cosolvent to a solute is accompanied by release of waters of hydration to the bulk. Our model clearly differentiates between the stoichiometric and non-stoichiometric interactions of solvent or co-solvent molecules with a solute. We analyzed the urea- and glycine betaine (GB)-induced conformational transitions of model proteins of varying size which are geometrically approximated by a sphere in their native state and a spherocylinder in their unfolded state. The free energy of cavity formation and its changes accompanying protein transitions were computed based on the concepts of scaled particle theory. The free energy of direct solute-cosolvent interactions were analyzed using empirical parameters previously determined for urea and GB interactions with low molecular weight model compounds. Our computations correctly capture the mode of action of urea and GB and yield realistic numbers for (∂ΔG°/∂a3)T,P which are related to the m-values of protein denaturation. Urea is characterized by negative values of (∂ΔG°/∂a3)T,P within the entire range of urea concentrations analyzed. At concentrations below ∼1 M, GB exhibits positive values of (∂ΔG°/∂a3)T,P which turn positive at higher GB concentrations. The balance between the thermodynamic contributions of cavity formation and direct solute-cosolvent interactions that, ultimately, defines the mode of cosolvent action is extremely subtle. A 20% increase or decrease in the equilibrium constant for solute-cosolvent binding may change the sign of (∂ΔG°/∂a3)T,P thereby altering the mode of cosolvent action (stabilizing to destabilizing or vice versa).

Swelling dynamics and swelling induced structural changes of polyelectrolyte ultrathin films

Swelling dynamics and swelling induced structural evolution of spin coated poly(sodium-4-styrenesulfonate) (NaPSS) ultrathin films in presence of water vapor have been studied using X-ray scattering and AFM techniques. Swelling dynamics of the films has been modelled in terms of the swelling of gyration ellipsoid of polyelectrolyte chains. In presence of water vapor swelling of these gyration ellipsoids is found to be independent of the film thickness. In presence of water vapor not only the thickness of the film increases but their in-depth and in-plane structures undergo continuous modification; that being different for thinner and thicker films. In–plane structural studies of the films indicate that undulations or faceting are present on film surface and contribution from each facet shows an oscillating behaviour with swelling time for thinner films. While for thicker films in-plane modification was unidirectional. The structural changes of the films in presence of water vapor are found to be permanent in nature for both thinner and thicker films and overall film quality diminishes on prolonged swelling. Pre and post annealing XRR data shows that rather than stress relaxation, solvent–molecule interaction is mainly responsible for the structural evolution of the polyelectrolyte films.

Structural, molecular orbital and optical characterizations of binuclear mixed ligand copper (II) complex of phthalate with N,N,N′,N′-tetramethylethylenediamine and its applications

A new binuclear mixed ligand complex, [Cu2(Phth)(Me4en)2(H2O)2(NO3)2]·H2O (where, Phth=phthalate, and (Me4en)=N,N,N′,N′tetramethylethylenediamine) was synthesized and characterized using analytical, spectral, magnetic, molar conductance, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The XRD data of Cu(II)-complex was analyzed on the basis of Williamson–Hall (W–H) and compared with TEM results. The results indicate that the complex is well crystalline and correspond to hexagonal crystal structure. Analysis of the absorption coefficient near the absorption edge reveals that the optical band gaps are indirect allowed transition with values of 1.17 and 1.78eV. The d–d absorption bands of the complex (dissolved in various solvents) exhibit a color changes (solvatochromic). Specific and non-specific interactions of solvent molecules with the complex were investigated using Multiple Linear Regression Analysis (MLRA). Transient photocurrent characteristics of Cu(II)-complex/n-Si heterojunctions indicate that photocurrent under illumination increase with increasing of light intensity and explained by continuous distribution of traps. Structural parameters of the free ligands and their Cu(II) – complex were calculated on the basis of semi-empirical PM3 level and compared with the experimental data. The present copper (II) complex was screened for its antimicrobial activity against some Gram-positive and Gram-negative bacteria and fungus strain.

Indomethacin Embedded into MIL-101 Frameworks: A Solid-State NMR Study

Interactions of drug molecules embedded within the pores of drug-delivery matrices significantly influence the drug-release rate and profile. In this Article, we used solid-state NMR experiments to inspect the interactions of indomethacin drug and tetrahydrofuran solvent molecules within mesoporous MIL-101 metal–organic framework materials. MIL-101 matrices were prepared using two types of linkers, terephthalic acid for MIL-101(Cr) and MIL-101(Fe), and amino-terephthalic acid for MIL-101(Al)-NH2 and MIL-101(Fe)-NH2. Loading MIL-101 matrices with indomethacin proved to be very efficient; the obtained delivery systems accommodated from 0.9 to 1.1 g of indomethacin per 1 g of MIL-101 material. NMR measurements showed that regardless of the type of the framework metal centers or the type of the organic linker indomethacin did not attach to the metal–organic framework. Interactions between indomethacin molecules themselves were also not detected. On the contrary, the smaller tetrahydrofuran solvent molecules d...

EPR Spectroscopy of Mercury-Organic Compounds with Nitroxide Radicals

Intramolecular electron spin exchange as a function of temperature, solvent viscosity and polarity has been studied by X-band electron paramagnetic resonance (EPR) spectroscopy for two nitroxide biradicals containing mercury-organic groups in the bridge connecting two 1-oxyl-2,2,6,6-tetramethylpiperidine-3,4-ene-nitroxide rings, R. The temperature dependence of the isotropic hyperfine splitting (hfs) constant a N and the exchange integral value |J/a| of the biradicals were measured from EPR spectra and subsequently analyzed comparing to a N and a Hg hfs constants of ClHgR radical dissolved in the same solvents. In all cases, the interaction of solvent molecules (SM) with >N–O fragments of nitroxide rings led to a slight decrease in a values with increasing temperature. The |J/a| value varied slightly with temperature T changes. The changes of |J/a| are much less comparing to those with variation of the solvent polarity. The interaction between SM and Hg atoms inside the bridge is observed and discussed.

Structural, molecular orbital and optical characterizations of solvatochromic mixed ligand copper(II) complex of 5,5-Dimethyl cyclohexanate 1,3-dione and N,N,N′,N′N″-pentamethyldiethylenetriamine

In this work, a new solvatochromic mononuclear mixed ligand complex with the formula, Cu(DMCHD)(Me5dien)NO3 (where, DMCHD=5,5-Dimethyl cyclohexanate 1,3-dione and (Me5dien)=N,N,N′,N′N″-pentamethyldiethylenetriamine was synthesized and characterized by analytical, spectral, magnetic, molar conductance, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The formation constant-value for copper (II)-DMCHD was found to be much lower than the expected for similar β-diketones, revealing monobasic unidentate nature of this ligand. The d–d absorption bands of the prepared complex exhibit a color changes in various solvent (solvatochromic). Specific and non-specific interactions of solvent molecules with the complex were investigated using Multi Parametric Linear Regression Analysis (MLRA). Structural parameters of the free ligands and their Cu (II) – complex were calculated on the basis of semi-empirical PM3 level and compared with the experimental data. The crystallite size and morphology of Cu(DMCHD)(Me5dien)NO3 were examined using XRD analysis and TEM, revealing that the complex is well crystalline and correspond to the monoclinic crystal structure. The lattice strain and mean crystallite size were estimated by Williamson–Hall (W–H) plot using X-ray diffraction data. The main important absorption parameters such as extinction molar coefficient, oscillator strength and electric dipole strength of the principal optical transitions in the UV–Vis region were calculated. The analysis of absorption coefficient near the fundamental absorption edge reveals that the optical band gaps are direct allowed transitions with values of 2.78eV and 3.59eV. The present copper (II) complex was screened for its antimicrobial activity against Staphylococcus Aureus and Bacillus Subtilis as Gram-positive bacteria, Escherichia Coli and Salmonella Typhimurium as Gram-negative bacteria and Candida Albicans as fungus strain.

Investigation of Ethanol–Peptide and Water–Peptide Interactions through Intermolecular Nuclear Overhauser Effects and Molecular Dynamics Simulations

Molecular dynamics simulations have been used to explore solvent-solute intermolecular nuclear Overhauser effects (NOEs) on NMR (nuclear magnetic resonance) signals of [val5]angiotensin dissolved in 35% ethanol-water (v/v). Consideration of chemical shift, coupling constant and intramolecular NOE data suggest that conformations of the peptide are adequately sampled by simulations of up to 0.6 μs duration. Calculated cross relaxation terms at 0 and 25 °C are compared to experimental values and to terms predicted using a particulate model of the solvent. Many calculated solvent NOEs are in agreement with experimental results; disagreements are particularly striking for hydrogens of the Phe8 residue of the peptide. Calculations show that individual molecules of either solvent component can spend many ns in association with the peptide but dipolar interactions within such a complex account for only a few percent of an observed cross relaxation rate. Most parts of the peptide interact selectively with ethanol. Diffusion of both solvent components is slowed when they are close to the peptide. Solvent-solute cross relaxation terms for acetic acid in the same solvent obtained from simulations agree with experiment. Preferential interactions of solvent molecules with acetic acid are largely absent, as are effects of this solute on solvent diffusion rates.