Organic Solvent Molecules Research Articles

Computational studies of the unusual water adduct [Cp2TiMe(OH2)](+): the roles of the solvent and the counterion.

The recently reported cationic titanocene complex [Cp2TiMe(OH2)](+) was subjected to detailed computational studies using density functional theory (DFT). The calculated NMR spectra revealed the importance of including the anion and the solvent (CD2Cl2) in order to calculate spectra which were in good agreement with the experimental data. Specifically, two organic solvent molecules were required to coordinate to the two hydrogens of the bound OH2 in order to achieve such agreement. Further elaboration of the role of the solvent led to Bader's QTAIM and natural bond order calculations. The zirconocene complex [Cp2ZrMe(OH2)](+) was simulated for comparison.

Variation and decomposition of the partial molar volume of small gas molecules in different organic solvents derived from molecular dynamics simulations

The partial molar volumes, V(i), of the gas solutes H2, CO, and CO2, solvated in acetone, methanol, heptane, and diethylether are determined computationally in the limit of infinite dilution and standard conditions. Solutions are described with molecular dynamics simulations in combination with the OPLS-aa force field for solvents and customized force field for solutes. V(i) is determined with the direct method, while the composition of V(i) is studied with Kirkwood-Buff integrals (KBIs). Subsequently, the amount of unoccupied space and size of pre-formed cavities in pure solvents is determined. Additionally, the shape of individual solvent cages is analyzed. Calculated V(i) deviate only 3.4 cm(3) mol(-1) (7.1%) from experimental literature values. Experimental V(i) variations across solutions are reproduced qualitatively and also quantitatively in most cases. The KBI analysis identifies differences in solute induced solvent reorganization in the immediate vicinity of H2 (<0.7 nm) and solvent reorganization up to the third solvation shell of CO and CO2 (<1.6 nm) as the origin of V(i) variations. In all solutions, larger V(i) are found in solvents that exhibit weak internal interactions, low cohesive energy density and large compressibility. Weak internal interactions facilitate solvent displacement by thermal solute movement, which enhances the size of solvent cages and thus V(i). Additionally, attractive electrostatic interactions of CO2 and the solvents, which do not depend on internal solvent interactions only, partially reversed the V(i) trends observed in H2 and CO solutions where electrostatic interactions with the solvents are absent. More empty space and larger pre-formed cavities are found in solvents with weak internal interactions, however, no evidence is found that solutes in any considered solvent are accommodated in pre-formed cavities. Individual solvent cages are found to be elongated in the negative direction of solute movement. This wake behind the moving solute is more pronounced in case of mobile H2 and in solvents with weaker internal interactions. However, deviations from a spherical solvent cage shape do not influence solute-solvent radial distribution functions after averaging over all solvent cage orientations and hence do not change V(i). Overall, the applied methodology reproduces V(i) and its variations reliably and the used V(i) decompositions identify the underlying reasons behind observed V(i) variations.

Superconductivity of alkali metal intercalated TiNBr with α-type nitride layers

TiNBr with α-type nitride layers (isostructural with FeOCl) was electron-doped by the intercalation of alkali metal (Li, Na, K, and Rb), which can be cointercalated with organic solvent molecules such as tetrahydrofuran (THF) and propylene carbonate (PC), expanding the basal spacing (d) up to 16 Å. All of the alkali metal intercalation compounds with and without cointercalation become superconductors with transition temperatures (Tc) up to 17.2 K. The Tc varies in a narrow temperature range against a wide range change of 0.1 < x < 0.46 in AxTiNBr. The Tc decreases linearly with the decreasing value of 1/d. The layer structured superconductors show a low anisotropy on the upper critical field (Hc2). These are characteristic features very similar to those found for the intercalation compounds of the Cl homolog TiNCl.

Laser-induced selective crosslinking for scaling the heterointerfacial domain in polymer blends

Organic blends containing heterojunction structures at the interfacial phase have been applied extensively in organic optoelectronic devices to modify charge transfer, separation, and recombination processes. Scaling and controlling the transition domains at the hetero-interface are of crucial importance for deep insights into the involved physics and for architecturing the devices with improved performance. However, it is difficult to recognize and characterize these transition domains directly using the conventional microscopic techniques, in particular when different molecules are dissolved in the same solvent with equal solubility. In this work, we introduce a technique defined as laser-induced selective cross-linking to isolate the interfacial phase from other phases into a directly measurable practicity. Thus, the hetero-domains become visualized and directly measurable. Based on the insolubility of the selectively cross-linked molecules in organic solvents, a lift-off process may remove the uncross-linked or incompletely cross-linked molecules, so that the hetero-domain is more clearly visualized and more precisely measured. A transition domain in a scale of about 200 nm is resolved in the F8BT/PFB blend film between their respectively rich phases after the selective cross-linking of the F8BT molecules by a blue laser. Furthermore, hetero-crosslinking between F8BT and PFB molecules was also resolved by both microscopic and near-field spectroscopic investigations.

Expansion of Access Tunnels and Active‐Site Cavities Influence Activity of Haloalkane Dehalogenases in Organic Cosolvents

The use of enzymes for biocatalysis can be significantly enhanced by using organic cosolvents in the reaction mixtures. Selection of the cosolvent type and concentration range for an enzymatic reaction is challenging and requires extensive empirical testing. An understanding of protein-solvent interaction could provide a theoretical framework for rationalising the selection process. Here, the behaviour of three model enzymes (haloalkane dehalogenases) was investigated in the presence of three representative organic cosolvents (acetone, formamide, and isopropanol). Steady-state kinetics assays, molecular dynamics simulations, and time-resolved fluorescence spectroscopy were used to elucidate the molecular mechanisms of enzyme-solvent interactions. Cosolvent molecules entered the enzymes' access tunnels and active sites, enlarged their volumes with no change in overall protein structure, but surprisingly did not act as competitive inhibitors. At low concentrations, the cosolvents either enhanced catalysis by lowering K(0.5) and increasing k(cat), or caused enzyme inactivation by promoting substrate inhibition and decreasing k(cat). The induced activation and inhibition of the enzymes correlated with expansion of the active-site pockets and their occupancy by cosolvent molecules. The study demonstrates that quantitative analysis of the proportions of the access tunnels and active-sites occupied by organic solvent molecules provides the valuable information for rational selection of appropriate protein-solvent pair and effective cosolvent concentration.

Self-assembly of organic-inorganic hybrid nanolayers: effect of endgroup polarity on nanostructures

Molecular self-assembly (MSA) offers a convenient way to elaborate highly ordered and lightweight nanostructures with molecular-level control of material structure, composition, and dimensions. This sub-branch of supramolecular chemistry which focuses on the spontaneous and reversible construction of ordered aggregates through weak intermolecular interactions represents a facile route to produce organic-inorganic hybrid nanolayers with long-range ordering. Over the past twenty years, many efforts have been devoted to the construction and structural optimization of well-ordered organic-inorganic nanolayers from monofunctional organosilane surfactants [1-3]. The organization process of such building blocks has been extensively investigated and is known to be governed mainly by the hydrophobic effect arising from a competition of attractive and repulsive interactions between inorganic polar heads, organic nonpolar tails, solvent and water molecules [4, 5]. Such interactions guide the nonpolar chains to aggregate and polar heads to maximize their exposure to the surrounding aqueous medium thus forming structures such as bilayers [6], micelles [7], or vesicles [8]. Finally, van der Waals forces appear between alkyl chains whereas hydrogen bonds and then stronger covalent bonds are formed between inorganic heads thus conferring thermal and mechanical stability to films [9, 10]. This study aims to investigate the effect on nanolayer structures of a second polar group located at the chain termination of alkylsilane building blocks. As intermolecular interactions which direct the assembly process are strongly dependent on the chemical composition of precursors, it is expected that the presence of a second polar endgroup will significantly affect these weak interactions thus leading to an alternative structure of nanolayers. Monofunctional hexadecyltrimethoxysilane (HDTMS) and bifunctional 11bromoundecyltrimethoxysilane (BUDTMS) were used independently as building blocks to produce organicinorganic nanolayers. Structures of these solid thin films were then sequentially characterized and compared after solution assembly and deposition on silicon substrates.

A dynamic, luminescent and entangled MOF as a qualitative sensor for volatile organic solvents and a quantitative monitor for acetonitrile vapour

A new luminescent entangled (srs nets with two-fold interpenetration, linked via short Cu⋯Cu distances of ca. 2.8 Å) MOF, namely, [(CuCN)3L·(guest)x]n (L = 2,6-bis((3,5-dimethyl-1H-pyrazol-4-yl)methyl)pyridine; x = 1 or 2), which contains microporous channels, is synthesized. This MOF material shows structural dynamics upon adsorption of various volatile organic solvent molecules, accompanied by reversible guest responsive colour changes of the fluorescence emission that are discernible by the naked eyes. The vacuated form of this material can also exhibit qualitative solvate-optical sensing behaviours toward various mixed solvents. Moreover, a quantitative real-time monitoring device is constructed that implements the determination of acetonitrile vapour pressure through optical response, which causes a drastic emission change from blue to yellow. The detailed structural elucidation provides structure–property understanding for the host–guest responsive dynamics.

PEGylation of Membrane Proteins Like Bacteriorhodopsin as a Tool to Increase Their Stability toward Ethanol

Protection of biological compounds, for example, enzymes, viruses, or even whole cells, against degradation is very important for many applications. Embedding of such compounds into polymer matrices is a straightforward common method. However, in biotechnology and medicine there is a great interest to prepare micro- and nanosized shells around the biocomponents in order to protect them and having only a minor increase in size. The PEGylation of biological macromolecules has gained attention because degradation by proteolytic enzymes is significantly retarded and, in turn, their bioavailability is enhanced. We found that PEGylation is also a powerful tool to protect biomaterials from degradation by small organic solvent molecules, in particular, ethanol. Methoxy-polyethylene glycol (MPEG) modified BR survives exposure to significant concentrations of ethanol, up to 30%, and preserves its photochromism, whereas unmodified PM is instantaneously denatured at such concentrations. This is useful for potential technical applications of BR but is of relevance for many other applications where biomaterials and, in particular, biomembranes may be exposed to solvents.

Complexation of different metals with a novel N-donor bridging receptor and Hirshfeld surfaces analysis

A novel N-donor bridging receptor R: 4,4′-methanediylbis(2-ethyl-5-methyl-1H-imidazole) has been synthesized from 2-ethyl-4-methyl-1H-imidazole and formaldehyde in the presence of potassium hydroxide. This receptor then formed complexes with different transition metals ([Co(NO3)2, CoCl2, Ni(NO3)2 and CuCl2]) in different solvent systems and obtained five different complexes. Wherein, the complex formation of R with Co(NO3)2 resulted in two different structures in methanol and acetonitrile, respectively. A thorough structural investigation of the present receptor and the resulted five complexes show that the NH group of the receptor, the organic anions and solvent molecules play a key role in the construction of the five intriguing architectures. We also prepared molecular Hirshfeld surface and fingerprint plot for R as well as the five complexes, which revealed the influences of different metals to the coordinate behavior of R in terms of intermolecular interactions.

Simple solvothermal synthesis of hydrophobic magnetic monodispersed Fe3O4 nanoparticles

A new solvothermal method is proposed for the preparation of Fe3O4 nanoparticles (NPs) from iron acetylacetonate in the presence of oleylamine and n-hexane. The products are characterized by X-ray powder diffraction, infrared (IR) spectroscopy, transmission electron microscopy, thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and vibrating sample magnetometery. The new procedure yields superparamagnetic monodispersed Fe3O4 particles with sizes ranging from 7nm to 12nm. The nanocrystal sizes are controlled by adjusting the volume ratio of oleylamine to n-hexane. IR and TG/DTG analyses indicate that the oleylamine molecules, as stabilizers, are adsorbed on the surface of Fe3O4 NPs as bilayer adsorption models. The surface adsorption quantities of oleylamine on 7.5 and 10.4 nm-diameter Fe3O4 NPs are 18% and 11%, respectively. The hydrophobic surface of the obtained nanocrystals is passivated by adsorbed organic solvent molecules. These molecules provide stability against agglomeration, enable solubility in nonpolar solvents, and allow the formation of magnetic polymer micelles.

Influence of Organic Solvents on Enzymatic Asymmetric Carboligations

The asymmetric mixed carboligation of aldehydes with thiamine diphosphate (ThDP)-dependent enzymes is an excellent example where activity as well as changes in chemo- and stereoselectivity can be followed sensitively. To elucidate the influence of organic additives in enzymatic carboligation reactions of mixed 2-hydroxy ketones, we present a comparative study of six ThDP-dependent enzymes in 13 water-miscible organic solvents under equivalent reaction conditions. The influence of the additives on the stereoselectivity is most pronounced and follows a general trend. If the enzyme stereoselectivity in aqueous buffer is already >99.9% ee, none of the solvents reduces this high selectivity. In contrast, both stereoselectivity and chemoselectivity are strongly influenced if the enzyme is rather unselective in aqueous buffer. For the S-selective enzyme with the largest active site, we were able to prove a general correlation of the solvent-excluded volume of the additives with the effect on selectivity changes: the smaller the organic solvent molecule, the higher the impact of this additive. Further, a correlation to log P of the additives on selectivity was detected if two additives have almost the same solvent-excluded volume. The observed results are discussed in terms of structural, biochemical and energetic effects. This work demonstrates the potential of medium engineering as a powerful additional tool for varying enzyme selectivity and thus engineering the product range of biotransformations. It further demonstrates that the use of cosolvents should be carefully planned, as the solvents may compete with the substrate(s) for binding sites in the enzyme active site.

Stabilization of Candida antarctica lipase B in hydrophilic organic solvent by rational design of hydrogen bond

Enzymatic reactions conducted in organic solvents have many advantages. However, organic solvent molecules may replace water molecules at the protein surface and penetrate into the enzyme, which could lead to the denaturation of the enzyme or changes in its reaction kinetics and substrate specificity. Thus, it is important to enhance the stability of enzymes in organic solvents. To date, there has been no efficient rational approach developed to enhance enzyme stability in hydrophilic solvents. We developed a rational approach to enzyme design. The design rules were established by investigating stable mutants from previous studies of directed evolution. Candida antarctica lipase B (CalB) was used as a target enzyme due to its versatile applications in organic solvents. The N97Q, N264Q, and D265E mutants of CalB showed higher organic solvent stability than the wild type.

Superconductivity in electron-doped layered TiNCl with variable interlayer coupling

Titanium nitride chloride (TiNCl), a band semiconductor with the $\ensuremath{\alpha}$-form layered structure, becomes a superconductor with a transition temperature ${T}_{c}\ensuremath{\approx}$ 18.0 K by electron doping via alkali-metal intercalation. Upon cointercalation of various kinds of organic solvent molecules with alkali atoms, the superconducting layered crystals are swelled to different extents adjusting to the size of the molecules, and the ${T}_{c}$ decreases linearly down to 6.5 K as a function of 1/$d$, where $d$ is the interlayer separation (basal spacing) of the expanded nitride layers, implying the importance of the Coulomb interlayer coupling for superconductivity. This is in strong contrast to a previous finding that the ${T}_{c}$ of the electron-doped ZrNCl and HfNCl with the $\ensuremath{\beta}$-form layered structure rather increases with the increase of $d$ upon a similar cointercalation of solvent molecules.

Interaction of organic solvents with protein structures at protein-solvent interface

The effect of non-denaturing concentrations of three different organic solvents, formamide, acetone and isopropanol, on the structure of haloalkane dehalogenases DhaA, LinB, and DbjA at the protein-solvent interface was studied using molecular dynamics simulations. Analysis of B-factors revealed that the presence of a given organic solvent mainly affects the dynamical behavior of the specificity-determining cap domain, with the exception of DbjA in acetone. Orientation of organic solvent molecules on the protein surface during the simulations was clearly dependent on their interaction with hydrophobic or hydrophilic surface patches, and the simulations suggest that the behavior of studied organic solvents in the vicinity of hyrophobic patches on the surface is similar to the air/water interface. DbjA was the only dimeric enzyme among studied haloalkane dehalogenases and provided an opportunity to explore effects of organic solvents on the quaternary structure. Penetration and trapping of organic solvents in the network of interactions between both monomers depends on the physico-chemical properties of the organic solvents. Consequently, both monomers of this enzyme oscillate differently in different organic solvents. With the exception of LinB in acetone, the structures of studied enzymes were stabilized in water-miscible organic solvents.

Solvent Effects on the Adsorption Geometry and Electronic Structure of Dye-Sensitized TiO2: A First-Principles Investigation

The performance of dye-sensitized solar cells (DSSCs) depends significantly on the adsorption geometry of the dye on the semiconductor surface. In turn, the stability and geometry of the adsorbed molecules is influenced by the chemical environment at the electrolyte/dye/TiO2 interface. To gain insight into the effect of the solvent on the adsorption geometries and electronic properties of dye-sensitized TiO2 interfaces, we carried out first-principles calculations on organic dyes and solvent (water or acetonitrile) molecules coadsorbed on the (101) surface of anatase TiO2. Solvent molecules introduce important modifications on the dye adsorption geometry with respect to the geometry calculated in vacuo. In particular, the bonding distance of the dye from the Ti anchoring atoms increases, the adsorption energy decreases, and the two C–O bonds in the carboxylic moieties become more symmetric than in vacuo. Moreover, the adsorbed solvent induces the deprotonation of the dye due to the changing the acid/base ...

Prediction of Aqueous Solubility of Organic Solvents as a Function of Selected Molecular Properties

Prediction of Aqueous Solubility of Organic Solvents as a Function of Selected Molecular Properties The aqueous solubility of 66 organic solvents was examined. As an organic solvent molecule is not always simple (single-carbon) organic species, the aqueous solubility was tested as a function of some selected molecular properties (descriptors); namely and using VolSurf+ notation, CP, D1, D2, D3, FLEX, G, HSA, LogKow, MW, PHSAR, POL, PSA, PSAR, R, S, V, W1, W2, and W3. In general, the organic solvent solubility data can be best described by the two molecular descriptors LogKow and R, with PHSAR as the third refining or tuning-up factor (weight function).

Density functional theory calculations of dynamic first hyperpolarizabilities for organic molecules in organic solvent: Comparison to experiment

Against experimental values obtained from solution-phase dc electric field induced second-harmonic generation measurements at a fundamental wavelength of 1910 nm, the performance of 20 exchange-correlation functionals in density functional theory in evaluation of solvent modulated dynamic first hyperpolarizabilities of 82 organic molecules in chloroform, 1,4-dioxane, and/or dichloromethane was evaluated. The used exchange-correlation functionals consisted of generalized gradient approximation (GGA), meta-GGA, global hybrids, and range-separated hybrids. The PCM-X/6-311+G(2d,p)//PCM-B3LYP/6-31G(2df,p) level of theory was employed. The calculated results showed functionals with the exact asymptote of the exchange potential gave satisfying linear correlation with R(2) of 0.95 between experimental data and theoretical values. With a linear correction, these functionals also provided a better accuracy with mean absolute error of 5 × 10(-30) esu than other functionals. The solvent effect and solvation scheme on the calculated property were also studied.

Microfluidic Device for the Crystallization of Organic Molecules in Organic Solvents

A microfluidic chip suitable for studying crystallization of organic molecules in organic solvents was developed. In this device, supersaturation can be generated either by thermal gradient (i.e., when the crystallization solvent is not miscible with the continuous phase) or by mass transfer (when the crystallization solvent is partially miscible with the continuous phase) or both. The experimental setup allows the storage of up to 2000 droplets to get nucleation statistics and crystal growth rates under static conditions. Crystallization of eflucimibe in droplets of octanol generated in water was investigated by use of this experimental device. The results show that, at lower time scale, the first nucleation events result mainly from a heterogeneous nucleation process (due to the presence of impurities or to the octanol–water interface itself). At higher time scales, the nucleation rate falls off, all the crystals appear in the droplet volume, and nucleation becomes homogeneous. This microfluidic device ...

Solubility of drug-like molecules in pure organic solvents with the CPA EoS

Solubility data in different solvents are an important issue for separation processes involving complex molecules such as natural products and pharmaceutical drugs. Nonetheless, solubility data are in general scarce and difficult to obtain, and so models are important tools to generate the necessary estimates. Different correlative, statistical and thermodynamic models have been proposed to evaluate solubilities. From these, the more theoretically sound thermodynamic models allow to generate estimates at broader temperature, pressure and composition conditions while using a smaller amount of experimental information. Among these, the cubic-plus-association equation of state that combines the simplicity and robustness of a cubic equation of state with the Wertheim's association contribution has been under attention. In this work, this EoS is for the first time proposed to model organic phase solubilities of drug-like molecules in a wide range of temperatures. Solubilities of acetanilide, acetylsalicylic acid, adipic acid, ascorbic acid, hydroquinone, ibuprofen, paracetamol and stearic acid were estimated in alcohols, ketones, alkanes, esters, acids, aromatics, chlorinated solvents, as well as in other common solvents. The hydrogen bonding behaviour was explicitly accounted for with each associating group being treated individually, as well as multiple group substitutions. Accurate correlations were obtained using a single binary interaction parameter (global AAD of 24.2%), while considering the complexity of the studied systems predictions were generally also satisfactory.

Regular Solution Theories Are Not Appropriate for Model Compounds for Petroleum Asphaltenes

The solubility, melting point temperature, and enthalpy of fusion of a series of model compounds for heavy petroleum fractions were measured experimentally in n-heptane, toluene, dichloromethane, and mixtures thereof. Two porphyrins (meso-tetraphenylporphyrin and octaethylporphyrin), the vanadyl analogues of the same two porphyrins, and one model asphaltene (4,4′-bis-(2-pyren-1-yl-ethyl)-[2,2′]bipyridinyl) were selected to test the efficacy of the regular solution and the Flory−Huggins theories in predicting the solubility behavior of these complex polyaromatic molecules in organic solvents. These simple solubility models were not capable of qualitatively or quantitatively describing the solubility behavior of these high-melting solid compounds, even with the solubility parameter as an adjustable parameter. Various different methods of estimating the differential heat capacity, ΔCP, improved the fits in certain cases, although no universally acceptable method was identified. Several group contribution the...