Tetrabutylphosphonium Hydroxide Research Articles

Untapping the coal reserves: Green desulfurization using phosphonium based ionic liquids

Thar coalfields of Pakistan are the 16th largest lignite coal reserves in the world. This untapped fuel source has high density for energy production. However, sulfur content limits its cleaner use the present research is a green practice for desulfurization of bituminous and lignite coal. For this purpose tetrabutylphosphonium hydroxide with anions precursor perchloric acid, dimethyl sulfate, and trifloromethanesulfonic acid was refluxed separately at room temperature to produce tetrabutylphosphonium trifloromethanesulfonate [P4444+][CF3SO3−], tetrabutylphosphonium perchlorate [P4444+][ClO4−], and tetrabutylphosphonium methyl sulfate [P4444+][MeSO4−]. The synthesized acidic nature phosphonium based room temperature ionic liquids (PRTILs) were characterized using standardized analytical techniques of FTIR, 1H NMR, 13C NMR, HPLC and TGA/DSC. TD50 order of PRTILs was 47 ºC< 253 ºC < 292 ºC for [P4444+][CF3SO3−], [P4444+][ClO4−], [P4444+][MeSO4−] respectively. The proximate and ultimate analysis of coal samples from Balochistan coal field indicated low moisture and high carbon content along with gross calorific value of 6938–7589 Kcal/Kg. The coal samples from Shahrig and Sor-range coal mines with highest sulfur content (6.9–11.8 %) were selected for desulfurization procedures by using PRTILs and assessed through FTIR, HPLC and CHNS analyzer. The solvents were found more effective in removal of thiophene, benzothiophene, and dibenzothiophene in an oxidative environment along with an increase of GCV of coal samples to 7204–7792 Kcal/Kg. The regeneration of spent PRTILs for three cycles in 25 % ethanol reveal them as sustainable solvents for the coal desulfurization process.

PH-Responsive Cellulose/Silk/Fe3O4 Hydrogel Microbeads Designed for Biomedical Applications.

In this study, cellulose/Fe3O4 hydrogel microbeads were prepared through the sol-gel transition of a solvent-in-oil emulsion using various cellulose-dissolving solvents and soybean oil without surfactants. Particularly, 40% tetrabutylammonium hydroxide (TBAH) and 40% tetrabutylphosphonium hydroxide (TBPH) dissolved cellulose at room temperature and effectively dispersed Fe3O4, forming cellulose/Fe3O4 microbeads with an average diameter of ~15 µm. Additionally, these solvents co-dissolved cellulose and silk, allowing for the manufacture of cellulose/silk/Fe3O4 hydrogel microbeads with altered surface characteristics. Owing to the negatively charged surface characteristics, the adsorption capacity of the cellulose/silk/Fe3O4 microbeads for the cationic dye crystal violet was >10 times higher than that of the cellulose/Fe3O4 microbeads. When prepared with TBAH, the initial adsorption rate of bovine serum albumin (BSA) on the cellulose/silk/Fe3O4 microbeads was 18.1 times higher than that on the cellulose/Fe3O4 microbeads. When preparing TBPH, the equilibrium adsorption capacity of the cellulose/silk/Fe3O4 microbeads for BSA (1.6 g/g) was 8.5 times higher than that of the cellulose/Fe3O4 microbeads. The pH-dependent BSA release from the cellulose/silk/Fe3O4 microbeads prepared with TBPH revealed 6.1-fold slower initial desorption rates and 5.2-fold lower desorption amounts at pH 2.2 than those at pH 7.4. Cytotoxicity tests on the cellulose and cellulose/silk composites regenerated with TBAH and TBPH yielded nontoxic results. Therefore, cellulose/silk/Fe3O4 microbeads are considered suitable pH-responsive supports for orally administered protein pharmaceuticals.

Bleaching-free, lignin-tolerant, high-yield production of nanocrystalline cellulose from lignocellulosic biomass

Nanocrystalline cellulose (NCC) preparation in an integrated fractionation manner is expected to solve the problems of low yield and environmental impact in the traditional process. An integrated fractionation strategy for NCC production from wood was developed through catalytic biomass fractionation, the partial dissolution of cellulose-rich materials (CRMs) in aqueous tetrabutylphosphonium hydroxide, and short-term ultrasonication. The presented process could tolerate a high CRM lignin content of 21.2wt% and provide a high NCC yield of 76.6wt% (34.3wt% of the original biomass). The increase in the CRM lignin content decreased the NCC yield, facilitated the crystal transition of NCC from cellulose I to cellulose II, and showed no apparent effects on the NCC morphology. A partial/selective dissolution mechanism is proposed for the presented strategy. This study provided a promising efficient fractionation-based method toward comprehensive and high-value utilization of lignocellulosic biomass through effective delignification and high-yield NCC production.

Influence of Temperature and pH Conditions on the Swelling Properties of Rice Straw Derived Cellulose Hydrogel

Cellulose, one of the renewable and biodegradable polymers, has been extensively studied as a raw material for a newly and fully bio-based hydrogel. The synthesis of bio-hydrogel is based on the dissolution of extracted cellulose from rice straw in tetrabutylphosphonium hydroxide (TBPH) solvent followed by the gelation using epichlorohydrin (ECH) crosslinkers. The success of the extraction of cellulose from rice straw was evaluated by characteristic peaks of cellulose in Fourier Transform Infrared Spectroscopy (FTIR) spectrum. The hydrogel formation mechanism was investigated in this article, as well as the evaluation of swelling properties under different temperature and pH conditions. As hydrogel exhibited thermal and pH sensitive behavior, the highest swelling capacity was found at pH 7.0 and 60 ºC. The characterization of hydrogel was examined by Fourier Transform Infrared Spectroscopy (FTIR) and thermal analysis (TGA), indicating that the rice straw derived cellulose hydrogel was cellulose type II, similar to others hydrogels. The morphology of extracted cellulose and hydrogel were investigated by Scanning Electron Microscope (SEM). The hydrogel exhibited porousity structure with very large pore size that surrounded by cellulose/ECH layers. The purity of the hydrogel was determined through the amount of water immersed in the hydrogel for one day by Liquid Nuclear Magnetic Resonance (NMR) for the residual TBPH determination.

(Digital Presentation) Physicochemical Characterization of Sulfonate-Based Phosphonium Ionic Liquids

Ionic liquids (ILs) have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. ILs are also promising liquid materials available for various applications because their function can be easily controlled by changing the combination of cations and anions and by introducing substituents. Although many kinds of ILs have already been investigated, phosphonium cation based ILs have rarely been proposed. We have previously designed and synthesized the phosphonium ILs together with typical sulfonylamide-based anions such as bis(trifluoromethylsulfonyl)amide and bis(fluorosulfonyl)amide anions.1,2) On the other hand, interests in phosphonium ILs consisting of the other anions is increasing for diverse applications. In this work, we design and prepare the ILs based on tetrabutylphosphonium cation (P4444 +) together with various sulfonate-based anions (Fig. 1), characterizing their physicochemical properties as a new family of ILs. The phosphonium IL was prepared by an aqueous neutralization reaction of tetrabutylphosphonium hydroxide with the stoichiometric amounts of various sulfonic acids. The obtained phosphonium ILs were isolated by water evaporation, and were dried in vacuo for at least 1 day. The physicochemical properties of ILs, e.g. density, viscosity, conductivity (ac impedance method) and thermal decomposition temperature (thermogravimetric analysis), were measured under argon atmosphere.The phosphonium salts based on unsubstituted sulfonate anions such as SO3CH3, SO3CH2CH3 and SO3(CH2)2CH3 were white crystalline solids at room temperature, whereas both amino- and hydroxy- substituted sulfonate salts were viscous liquids at room temperature. All phosphonium salts obtained were hydrophilic. Table 1 summarizes the physicochemical properties of phosphonium ILs based on amino- and hydroxy-substituted sulfonate anions. These phosphonium ILs exhibited considerably high viscosities when compared to the previously published viscosity value of P4444-lactate IL (415 mPa s at 25 °C)3), which suggests that the electrostatic interaction between P4444 cation and the sulfonate anions is much stronger than those in the case of carboxylate-based phosphonium ILs. It should be noted that P4444-SO3(CH2)3NH2 obviously indicated not only the highest density but also the highest viscosity and the lowest conductivity, which might be due to the fact that the IL has the largest anion to give a significant van der Waals interaction. Figure 1

Green extraction processing of lutein from Chlorella saccharophila in water-based ionic liquids as a sustainable innovation in algal biorefineries

A billion tonnes of waste are generated every year in the food industry. Green extraction of natural antioxidants and therapeutics like carotenoids from microalgae using ionic liquids may help in improving the process efficiency and reducing the dependency on petroleum-based chemicals in the food industry. The extraction of carotenoids is solvent specific, and extraction efficiency varies greatly. The effect of 4 different ILs on carotenoid profiles of C. saccharophila was assessed and compared to a conventional solvent, methanol, to check their extractability. We found 40 % (w/v) Tetrabutyl phosphonium hydroxide as the best IL to extract the carotenoids. Tetrabutyl phosphonium hydroxide selectively extracts 2.26 mg g−1 dry cell weight (DCW) of lutein from wet biomass of C. saccharophila, whereas methanol extracts 0.10 mg g−1 DCW of lutein at room temperature-based extraction. Also, the combinatorial effect of temperature, extraction time, solvent: biomass ratio and ionic liquid concentration was investigated using a statistical modelling technique, Response Surface Modelling (RSM). It was found that lutein extraction is further improved by 10 % to 2.49 mg g−1 under the optimal extraction conditions [40 % (w/v) Ionic liquid concentration, 5 min extraction time, 0.5 (mL mg−1) Solvent: Biomass Ratio and 25 °C temperature]. Lutein remains 3 times more stable in IL than in conventional solvent methanol at 60 and 90 °C. Hence, Tetrabutyl phosphonium hydroxide can prospectively substitute conventional organic solvents in the downstream processing of bioactive compounds from microalgae.

Simple synthesis of cellulose hydrogels based on the direct dissolution of cellulose in tetrabutylphosphonium hydroxide followed by crosslinking

AbstractCellulose‐based hydrogels are valuable sustainable materials with significant potential applications in biomedical fields such as cell therapy, hemostasis, wound healing, tissue transplantation, regeneration technology, and drug delivery carrier to cells. In contrast to previous studies, the standard synthesis procedure needs high temperature, low cellulose concentration, and many additives. Here cellulose‐based hydrogels with a high cellulose concentration are produced at room temperature. The one‐pot preparation of chemical hydrogels involves the dissolution of cellulose in tetrabutylphosphonium hydroxide followed by epichlorohydrin crosslinking. The effects of the wide range of microcrystalline cellulose concentrations and the crosslinker ratio on swelling properties and crosslink density under different conditions are investigated. The hydrogels are characterized using Fourier transform infrared spectroscopy and X‐ray diffraction. The morphology of hydrogels is examined through scanning electron microscope. The transparency of hydrogel is determined by ultraviolet–visible (UV–vis) spectrophotometer.

Tuning the density of Brønsted acid sites on mesoporous ZSM-5 zeolite for enhancing light olefins selectivity in the catalytic cracking of n-octane

A molecular template (tetrapropylammonium hydroxide, TPAOH) and a phosphorus-containing template (tetrabutylphosphonium hydroxide, TBPOH or tetrabutylphosphonium bromide, TBPBr) were used as dual templates to prepare the mesoporous ZSM-5 zeolites. The physicochemical properties of the as-prepared ZSM-5 catalysts were characterized by means of XRD, N2 adsorption, NH3-TPD, FT-IR spectra of adsorbed pyridine, 27Al MAS NMR, etc., and their performances for the catalytic cracking of the n-octane to light olefins were investigated. The results indicated that the acidity of ZSM-5, especially the concentration of strong Brønsted acid sites (SBAS) can be finely modulated by tuning the molar ratio of TPA+/TBP+. The charge-compensation effect of TBP+ and the phosphorus species played critical roles in regulating the SBAS concentrations of ZSM-5. Consequently, the as-prepared ZSM-5 catalysts with suitable strong Brønsted acid sites density was favorable for enhancing the selectivity to light olefins. At the temperature of 600 °C, the selectivity of propene and light olefins over MFI-9/2.5 catalyst were achieved 34.7% and 70.4%, which were higher than those over conventional ZSM-5 by 2.4% and 5.1%, respectively. Selectivity to C2=∼C4= light olefins was found to be decreased with increasing the concentration of strong Brønsted acid sites due to the reduction of SBAS which inhibited the hydrogen transfer reaction. This work will provide insights and new platforms for the design of high-efficiency zeolite catalysts for important industrial reactions.

Facile isolation and analysis of sporopollenin exine from bee pollen

We present facile methods to obtain purified sporopollenin exine capsules, and provide mass balances for classical and novel purification procedures. An ionic liquid, tetrabutyl phosphonium hydroxide turned out to be the most effective in removing the intine wall. The sporopollenin capsules were investigated by fluorescent microscopy, AFM, solid-state NMR and infrared Raman spectroscopy. The latter two methods showed that sunflower and rape exines have different proportions of O-aliphatic and aromatic constituents. Purified exine capsules were coated with functionalized fluorophores. The procedures presented in this paper could contribute to further spread of the applications of this hollow, and chemically highly resistant material.

Compound heterozygous variants in Wiskott-Aldrich syndrome like (WASL) gene segregating in a family with early onset Parkinson's disease

BackgroundKnowledge of genetic determinants in Parkinson's disease is still limited. Familial forms of the disease continue to provide a rich resource to capture the genetic spectrum in disease pathogenesis, and this approach is exploited in this study. MethodsInformative members from a three-generation family of Indian ethnicity manifesting a likely autosomal recessive mode of inheritance of Parkinson's disease were used for whole exome sequencing. Variant data analysis and in vitro functional characterisation of variant(s) segregating with the phenotype were carried out in HEK-293 and SH-SY5Y cells using gene constructs of interest. ResultsTwo compound heterozygous variants, a rare missense (c.1139C > T:p.P380L) and a novel splice variant (c.1456 + 2 delTAGA, intron10) in Wiskott-Aldrich syndrome like gene (WASL, 7q31), both predicted to be deleterious were shared among the proband and two affected siblings. WASL, a gene not previously linked to a human Mendelian disorder is known to regulate actin polymerisation via Arp2/3 complex. Based on exon trapping assay using pSPL3 vector in HEK-293 cells, the splice variant showed skipping of exon10. Characterisation of the missense variant in SH-SY5Y cells demonstrated: i) significant alterations in neurite length and number; ii) decreased reactive oxygen species tolerance in mutation carrying cells on Tetrabutylphosphonium hydroxide induction and iii) increase in alpha-synuclein protein. Screening for WASL variants in two independent PD cohorts identified four individuals with heterozygous but none with biallelic variants. ConclusionWASL, with demonstrated functional relevance in neurons may be yet another strong candidate gene for autosomal recessive PD encouraging assessment of its contribution across populations.

Improvement of lipid solubility and oral bioavailability of a poorly water- and poorly lipid-soluble drug, rebamipide, by utilizing its counter ion and SNEDDS preparation

Among drugs in development and/or in market, there are poorly water-soluble and poorly lipid-soluble compounds. Rebamipide, classified into BCS class IV, is one of those drugs which provide very low bioavailability and/or the difficulty of formulation for oral administration. Because of its low solubility in available lipoidal excipients, it was impossible to prepare an adequate SNEDDS formulation of rebamipide. Then, we tried to increase the solubility of rebamipide in lipoidal excipients for preparing a more practical SNEDDS formulation by making the complex with its counter ion, tetrabutylphosphonium hydroxide (TBPOH) or NaOH. Rebamipide concentration in ethanol was proportionally increased with the increment of TBPOH or NaOH added, indicating that the formation of complex with a counter ion should contribute to the solubilization of rebamipide in ethanol. Both Rebamipide-TBPOH complex (Reb-TBPOH) and Rebamipide-NaOH complex (Reb-NaOH) obtained by lyophilization showed no endothermic peak in DSC and no diffraction peak in XRPD, suggesting that the solid state of both complexes should be amorphous. Reb-TBPOH maintained the dissolution of rebamipide in SNEDDS vehicle (Capryol 90:Cremophor EL:Transcutol P = 4:3:3) at 20 mg/g at least for 28 days, while Reb-NaOH did it at 10 mg/g. In vitro dissolution study showed that Reb-TBPOH SNEDDS and Reb-NaOH SNEDDS containing rebamipide at 10 mg/g maintained the complete dissolution of rebamipide in FaSSIF (intestinal luminal condition). In the gastric luminal condition (pH3.9 acetate buffer), the high concentration, close to the complete dissolution, was transiently observed and quickly decreased to one-sixth of the maximum, but it was still around 70 times higher than that of the crystalline powder. The additional utilization of Eudragit EPO for SNEDDS preparations of both complexes successfully maintained the high concentrations of rebamipide in the gastric luminal condition. In vivo oral absorption studies clearly indicated that SNEDDS preparations utilizing Reb-counter ion complex successfully improved rebamipide absorption.

Comprehensive utilization strategy of cellulose in a facile, controllable, high-yield preparation process of cellulose nanocrystals using aqueous tetrabutylphosphonium hydroxide

Tetrabutylphosphonium hydroxide treatment of cellulose enabled facile, controllable, high-yield preparation of cellulose nanocrystals and effective enzymatic hydrolysis of cellulosic residue, resulting in a high utilization rate of more than 95%.

Long-range ordering of two-dimensional wide bandgap tantalum oxide nanosheets in printed films.

Two-dimensional oxide materials are a well-studied, interesting class of materials, enabled by the fact that their bulk layered metal oxides, such as titanates and niobates, can be easily exfoliated within minutes into 2D nanosheets. However, some promising oxide materials, such tantalum oxide, are much more difficult to delaminate, taking several weeks, due to the higher charge density resulting in stronger Coulombic interactions between the layers. This intrinsic constraint has limited detailed studies for exploiting the promising properties of tantalum oxide 2D nanosheets towards enhanced catalysis and energy storage. Here, we have studied in detail the exfoliation mechanism of high charge density 2D materials, specifically tantalum oxide (TaO3) nanosheets. Optimization of tetrabutylphosphonium hydroxide (TBPOH) as the exfoliation agent in a 2 : 1 ratio to HTaO3 has resulted in a dramatic reduction of the exfoliation time down to only 36 hours at 80 °C. Furthermore, single monolayers of TaO3 nanosheets with >95% coverage have been achieved by Langmuir–Blodgett deposition, while thicker layers (ranging from several tens of nanometers up to microns) exhibiting long-range ordering of the present nanosheets have been realized through inkjet printing. Interestingly, scanning tunneling microscopy analysis indicated a wide bandgap of ∼5 eV for the single TaO3 nanosheets. This value is significantly higher than the reported values between 3.5 and 4.3 eV for the layered RbTaO3 parent compound, and opens up new opportunities for 2D oxide materials.

Toward a facile fabrication route for all-cellulose composite laminates via partial dissolution in aqueous tetrabutylphosphonium hydroxide solution

The potential for a facile aqueous-based solvent processing route for the synthesis of all-cellulose composites (ACCs) is explored using aqueous solutions containing tertabutylphosphonium hydroxide (TBPH). Specifically, ACC laminates are prepared via the partial dissolution of a woven textile of cellulose II using aqueous TBPH solutions. The dissolved cellulose was then regenerated to reform a cellulose II matrix phase in situ that acts to bond the original undissolved fibres. The hygroscopic behaviour and dissolution analysis of the solvent system showed wide range in the choice of processing conditions suited to the production of ACC laminates via TBPH. The effect of solvent concentration on the microstructure, crystallinity and tensile properties of ACCs is reported. The use of TBPH enables reductions in the processing cycle time and improved control over the properties of ACCs, indicative of a promising solvent system for the upscaled production of ACCs and their laminates.

Effect of Cellulose Solvents on the Characteristics of Cellulose/Fe2O3 Hydrogel Microspheres as Enzyme Supports.

Cellulose hydrogels are considered useful biocompatible and biodegradable materials. However, as few cellulose-dissolving solvents can be used to prepare cellulose hydrogel microspheres, the use of unmodified cellulose-based hydrogel microspheres for enzyme immobilization remains limited. Here, we prepared cellulose/Fe2O3 hydrogel microspheres as enzyme supports through sol-gel transition using a solvent-in-oil emulsion. Cellulose-dissolving solvents including 1-ethyl-3-methylimidazolium ([Emim][Ac]), an aqueous mixture of NaOH and thiourea, tetrabutylammonium hydroxide, and tetrabutylphosphonium hydroxide were used to prepare regular shaped cellulose/Fe2O3 microspheres. The solvent affected microsphere characteristics like crystallinity, hydrophobicity, surface morphology, size distribution, and swelling properties. The immobilization efficiency of the microspheres for lipase was also significantly influenced by the type of cellulose solvent used. In particular, the lipase immobilized on cellulose/Fe2O3 microspheres prepared using [Emim][Ac] showed the highest protein loading, and its specific activity was 3.1-fold higher than that of free lipase. The immobilized lipase could be simply recovered by a magnet and continuously reused.

Coagulation using organic carbonates opens up a sustainable route towards regenerated cellulose films

Due to their biodegradability, biocompatibility and sustainable nature, regenerated cellulose (RC) films are of enormous relevance for green applications including medicinal, environmental and separation technologies. However, the processes used so far are very hazardous to the environment and health. Here, we disclose a simple, fast, environmentally friendly, nontoxic and cost-effective processing method for preparing RC films. High quality non-transparent and transparent RC films and powders can be produced by dissolution with tetrabutylphosphonium hydroxide [TBPH]/[TBP]+[OH]− followed by coagulation with organic carbonates. Investigations on the coagulation mechanism revealed an extremely fast reaction between the carbonates and the hydroxide ions. The high-quality powders and films were fully characterized with respect to structure, surface morphology, permeation and selectivity. This method represents a future-oriented green alternative to known industrial processes.

Facile Preparation and Tribological Properties of Water-Based Naphthalene Dicarboxylate Ionic Liquid Lubricating Additives

Taking 1,4-naphthalene dicarboxylic acid (1,4-ND), 2,3-naphthalene dicarboxylic acid (2,3-ND) and tetrabutyl ammonium hydroxide (N4444OH), tetrabutyl phosphonium hydroxide (P4444OH) as raw materials, water-based lubricant additives tetrabutyl ammonium 1,4-naphthalene dicarboxylate (1,4-NDN4444), tetrabutyl phosphonium 1,4-naphthalene dicarboxylate (1,4-NDP4444), tetrabutyl ammonium 2,3-naphthalene dicarboxylate (2,3-NDN4444), and tetrabutyl phosphonium 2,3-naphthalene dicarboxylate (2,3-NDP4444) were prepared in aqueous solution. The additives are not only simple to prepare, but also have good solubility in water. More importantly, they can significantly improve the friction reducing and anti-wear performances of water. On account of the mechanism analysis, it is estimated that the introduction of aromatic ring and more carboxyl groups to the additives play an important role for them to form stable lubrication protective films during the friction process and then to achieve excellent lubrication performance on steel/steel, copper/steel, and aluminum/steel friction pairs. Remarkably, the performances of 2,3-NDN4444 and 2,3-NDP4444 are superior to those of 1,4-NDN4444 and 1,4-NDP4444, which is ascribed to their stronger adsorption on the metal surfaces contributed by the two adsorption targets (two –COO− groups). For 1,4-NDN4444 and 1,4-NDP4444, there is only one –COO− group that can be simultaneously adsorbed on the metal surfaces from the perspective of space configuration. It weakens the adsorption and decreases the effectiveness of the lubrication protective films resulting in the reduced friction reducing and anti-wear properties of 1,4-NDN4444 and 1,4-NDP4444. Water-based lubricant additives tetrabutyl ammonium 1,4-naphthalene dicarboxylate (1,4-NDN4444), tetrabutyl phosphonium 1,4-naphthalene dicarboxylate (1,4-NDP4444), tetrabutyl ammonium 2,3-naphthalene dicarboxylate (2,3-NDN4444) and tetrabutyl phosphonium 2,3-naphthalene dicarboxylate (2,3-NDP4444) were prepared in aqueous solution. The additives are not only simple to prepare, but also have good solubility in water. More importantly, they can significantly improve the friction reducing and anti-wear performances of water. Evolution of the friction coefficients (a) and wear volume losses (b) for different samples on steel/steel friction pairs.

Crystallographic evidence of Watson–Crick connectivity in the base pair of anionic adenine with thymine

Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N4444]+) or tetrabutylphosphonium ([P4444]+) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N4444][Ad]·2H2O, and thymine, [P4444][Thy]·2H2O, as well as the double salt cocrystal, [P4444]2[Ad][Thy]·3H2O·2HThy. The cocrystal includes the anionic [Ad-(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson-Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.

Visible Light-Driven Photoreduction of CO2 to CH4 over TiO2 Using a Multiple-Site Ionic Liquid as an Absorbent and Photosensitizer

A novel four-site ionic liquid (IL) was designed via the neutralization of citrazinic acid with tetrabutylphosphonium hydroxide, which had the highest CO2 absorption capacity of 3.26 mol per molar ...

Thermodynamic and Transport Properties of Tetrabutylphosphonium Hydroxide and Tetrabutylphosphonium Chloride–Water Mixtures via Molecular Dynamics Simulation

Thermodynamic, structural, and transport properties of tetrabutylphosphonium hydroxide (TBPH) and tetrabutylphosphonium chloride (TBPCl)–water mixtures have been investigated using all-atom molecular dynamics simulations in response to recent experimental work showing the TBPH–water mixtures capability as a cellulose solvent. Multiple transitional states exist for the water—ionic liquid (IL) mixture between 70 and 100 mol% water, which corresponds to a significant increase in water hydrogen bonds. The key transitional region, from 85 to 92.5 mol% water, which coincides with the mixture’s maximum cellulose solubility, reveals small and distinct water veins with cage structures formed by the TBP+ ions, while the hydroxide and chloride ions have moved away from the P atom of TBP+ and are strongly hydrogen bonded to the water. The maximum cellulose solubility of the TBPH–water solution at approximately 91.1 mol% water, appears correlated with the destruction of the TBP’s interlocking structure in the simulations, allowing the formation of water veins and channeling structures throughout the system, as well as changing from a subdiffusive to a near-normal diffusive regime, increasing the probability of the IL’s interaction with the cellulose polymer. A comparison is made between the solution properties of TBPH and TBPCl with those of alkylimidazolium-based ILs, for which water appears to act as anti-solvent rather than a co-solvent.