Polar Aprotic Solvents Research Articles

Solvent-engineered performance improvement of graphene quantum dot sensitized solar cells with nitrogen functionalized GQD photosensitizers

We report for the first time that the choice of solvent used in the synthesis of nitrogen-doped graphene quantum dots (N-GQDs) has a significant effect on the photovoltaic performance of quantum dot sensitized solar cells (QDSSC) where N-GQDs work as photosensitizers. Switching from protic water (H2O) solvent to aprotic N-N dimethylformamide (DMF) causes significant change in structural, photophysical and electronic properties of N-GQDs working as active materials in QDSSC. Unlike traditional dye-sensitized solar cells, N-GQDs replace toxic and readily degradable organic dyes as an active material, due to enhanced stability, cost-efficient fabrication, and environment-friendly processing. We discussed compositional, optical, and electronic properties of N-GQDs synthesized in different solvents, and their role in the photoconversion efficiency of quantum dots sensitized solar cells. Spectroscopic results reveal that nitrogen-doped graphene quantum dots with green emission (G-GQDs) have relatively shorter effective conjugation length and lower content of pyrrolic nitrogen groups because water is a polar protic solvent, which suppresses the water elimination reaction by donating protons to the reaction medium. On the contrary, DMF, a polar aprotic solvent, cannot donate hydrogen, leading to enhanced nitrogen units in the graphene quantum dots framework and red emission (R-GQDs), thus improving carrier density and transport properties. QDSSCs fabricated from R-GQDs exhibit photovoltaic performance (PCE > 5.0%) superior to other previously reported GQD sensitized solar cells.

Novel insights into the mechanism for protic solvent promoting Pd/C-catalyzed hydrodechlorination of chlorinated organic compounds

• Protic solvents promoted catalytic HDC of 4-CBP with Et 3 N over Pd/C catalyst. • HDC rate of 4-CBP increased with increase of water content in mixed solvent systems. • Mechanism for protic solvents promoting Pd/C-catalyzed HDC reactions was elucidated. • Protic solvents participated in Pd/C-catalyzed HDC and hydrogenation reactions. Solvent effects in liquid-phase hydrodechlorination (HDC) of chlorinated organic compounds (COCs) over Pd/C catalyst were systematically studied. For the HDC of 4-chlorobiphenyl (4-CBP) with triethylamine (Et 3 N), Pd/C exhibited much higher catalytic activity in protic solvents than that in aprotic polar and non-polar solvents, and a clear correlation between the HDC rate and polarity of protic solvents was observed. Moreover, water promoted Pd/C-catalyzed HDC of 4-CBP in homogeneous alcohol-water solvents and biphasic organic-water solvents with Et 3 N, and the HDC rate of 4-CBP increased with the increase of water content in the above solvent systems. Catalyst characterization (FT-IR and XRD) combined with solvent parameters and isotope labelling analysis were introduced to explain in-depth the solvent effects in the HDC of 4-CBP with Et 3 N. It was found that protic solvents would transfer active hydrogen atom (H*) via hydrogen bonding network or exchange their hydroxyl hydrogen with H*, which was beneficial to the stabilization of H* and interface HDC reaction. Thus, the higher HDC rate was achieved in solvent systems contained protic solvents with higher hydrogen-bond donor capability ( α ) values. On the other hand, non-polar and polar aprotic solvents had a negative effect on H* and mass transfer, and thus suppressed interface HDC reaction. Similar solvent effects were observed in Pd/C-catalyzed hydrogenation of unsaturated bonds-containing groups (nitryl group, carbonyl group, and carbon-carbon double bond). The results presented here would provide vital guidance for the rational selection of solvent systems for Pd/C-catalyzed HDC of COCs and hydrogenation of unsaturated bonds-containing groups.

Electrocarboxylation of Spiropyran Switches through Carbon‐Bromide Bond Cleavage Reaction

AbstractThis manuscript deals with carbon capture and utilization to synthetize high‐added chemicals using CO2 as a C1‐organic building block for C−C bond formation. The study focuses on the electrocarboxylation of 1,3,3‐trimethylindolino‐6′‐bromobenzopyrylospiran switch (Br‐BIPS). Prior to the electrocarboxylation process, the electrochemical reduction mechanism of Br‐BIPS and CO2 is disclosed in polar aprotic solvents using two different cathodes (glassy carbon and silver) under nitrogen atmosphere. Once the role of the cathode in the reduction carbon‐bromide bond cleavage is understood, carboxylated spiropyran derivatives can be synthesized in moderate yields and conversion rates through an electrocarboxylation process using CO2 silver cathode and polar aprotic solvents. The “green” efficient route described in the current work would open a new sustainable strategy for designing and building “smart” surfaces with switchable physical properties.

Bio-Availability, Anticancer Potential, and Chemical Data of Lycopene: An Overview and Technological Prospecting.

The purpose of this review was to collect relevant chemical data about lycopene and its isomers, which can be extracted using different non-polar or polar aprotic solvents by SC-CO2 or biosynthesis as a friendly technique. Lycopene and other carotenoids can be identified and quantified by UV–Vis and HPLC using a C18 or C30 column, while their characterization is possible by UV–Vis, Fluorescence, FTIR, MS, NMR, and DSC assays. Among these techniques, the last four can compare lycopene isomers and identify cis or all-trans-lycopene. FTIR, MS, and NMR techniques are more suitable for the verification of the purity of lycopene extracts due to the signal complexity generated for each isomer, which enables identification by subtle differences. Additionally, some biological activities of lycopene isolated from red vegetables have already been confirmed, such as anti-inflammatory, antioxidant, and cytotoxic activity against cancer cells, probably by activating several pathways. The encapsulation of lycopene in nanoparticles demonstrated an improvement in oral delivery, and ex vivo assessments determined that these nanoparticles had better permeation and low cytotoxicity against human cells with enhanced permeation. These data suggest that lycopene has the potential to be applied in the food and pharmaceutical industries, as well as in cosmetic products.

Highly atom efficient synthesis of 2,2,4,5-tetrasubstituted 3(2H)-furanones having both hydroxyl and amino substituents

We have developed a highly atom efficient synthesis of tetrasubstituted 3(2H)-furanones from easily accessible starting materials such as C,N-diarylaldonitrones and dibenzoylacetylene. Control experiments revealed that reaction of aldonitrones having electron-withdrawing groups on the C-aryl substituent in polar aprotic solvents exhibited high product selectivity while reaction temperature has only a negligible effect on product yield and selectivity.

New polyamides based on diacid with decanediamide and methylene groups and aromatic diamines

AbstractA new aromatic diacid, containing preformed diamide functional group, C8 alkylene moiety, and two methylene spacers, viz; N, N′‐bis(4′‐carboxy methylene phenyl) decane diamide (BCPDD) was designed and successfully synthesized. The structure of BCPDD was confirmed by FT‐IR, NMR (1H, 13C) spectroscopy and mass spectrometry. The corresponding series of new polyamides were prepared via reactions of diacid (BCPDD) and commercial aromatic diamines by Yamazaki's phosphorylative direct polycondensation method. Physical properties of these polyamides such as inherent viscosity, solubility in organic solvents, glass transition temperatures by DSC, thermal stability by TGA, and amorphous‐crystalline mature by XRD were studied. The incorporation of preformed amide, methylene spacers, and C8 alkylene moiety greatly affected polyamide properties such as solubility in common organic polar solvents, glass transition temperature, and thermal stability. These polyamides were mostly amorphous in nature and dissolved in polar aprotic solvents such as N‐methyl‐2‐pyrrolidone, N, N‐dimethylacetamide, N, N‐dimethylformamide, dimethyl sulfoxide, m‐cresol, and pyridine. Inherent viscosities of these polyamides were in the range of 0.40–0.67dL/g; indicating the formation of moderate to high molecular weights. These polyamides exhibited good thermal stability having temperatures for 10% weight loss (T10) in the range of 404–578°C and the char yields at 800°C in the range of 35–65%. The glass transition temperatures; as determined by DSC were in the range of 204–235°C.

Acid-Catalyzed Condensation of Benzamide with Glyoxal, and Reaction Features.

Scholars from around the world have been attempting to simplify and cheapen the synthetic method for the promising high-energy compound CL-20 for decades. The lack of understanding of the formation mechanisms of hexaazaisowurtzitane derivatives―CL-20 precursors―is a barrier to solving the said problems. Here, we report the results from an in-depth study into the acid-catalyzed condensation between benzamide and glyoxal in a molar ratio of 2:1 in polar protic and aprotic solvents. Sixteen compounds were isolated and identified, of which eight were synthesized for the first time. A geminal diol, N,N’-(2,2-dihydroxyethane-1,1-diyl)dibenzamide, was synthesized. Two isomers of 1,2-bis(benzoylamino)-1,2-ethanediol were isolated and identified. N,N’-(1-oxoethane-1,2-diyl)dibenzamide and 2-oxo-2-[(phenylcarbonyl)amino]ethyl benzoate were produced that were likely formed due to the 1,2-hydride shift. N-polysubstituted 1,4-dioxane-2,3,5,6-tetramine was synthesized for the first time, whose structure may be of interest as a scaffold for new explosives. DMSO, THF and HCOOH were found to be able to engage in a reaction with benzamide, or condensation products thereof, and glyoxal under acid-catalyzed conditions.

Preparation of defect-free asymmetric gas separation membranes with dihydrolevoglucosenone (CyreneTM) as a greener polar aprotic solvent

Nonsolvent-induced phase separation (NIPS) is widely used to prepare asymmetric gas separation membranes. Most industrial NIPS casting solution formulations are limited to a small group of glassy polymers and, importantly, require toxic polar aprotic solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or N-methyl-2-pyrrolidone (NMP). Growing restrictions on the use of such solvents are spurring the search for more benign casting solution formulations that do not compromise membrane performance. This study reports high-flux, defect-free asymmetric polysulfone (PSf) gas separation membranes prepared using dihydrolevoglucosenone (CyreneTM), a polar aprotic solvent that is believed to be safer than DMAc, DMF, and NMP, as the majority casting solution component. Optimized formulations and casting conditions produce membranes with hydrogen permeances exceeding 100 gas permeance units (GPU) and selectivities at or above those of dense PSf films. Dry/wet NIPS membrane performance improved with shorter dry step times and increased CyreneTM loadings relative to the volatile solvent, tetrahydrofuran (THF), in the casting solution. The high water-CyreneTM Flory-Huggins interaction parameter, χ12, and high casting solution viscosities help suppress the formation of skin layer defects and sublayer macrovoids. In some cases, membrane selectivities were influenced by substructure resistance, providing insight into the relationship between sublayer morphology and membrane performance.

An ultrapermeable thin film composite membrane supported by “green” nanofibrous polyimide substrate for polar aprotic organic solvent recovery

The preparation of polymeric-based thin film composite (TFC) membrane with high permeance and superior solvent resistance in organic solvent nanofiltration (OSN) applications always involves the consumption of toxic chemicals or high energy, which does not meet the requirements of green chemistry. In this work, intrinsic insoluble polyimide (PI) nanofiber substrates were obtained by a two-step method including electrospinning of poly (amic acid) synthesized by polycondensation reaction between various monomers and subsequent thermal imidization, and the optimized one with low thermal imidization temperature was employed as substrate for TFC membrane in strong polar aprotic solvents recovery, therefore achieving the green process. The effects of different dianhydride and diamine monomers and different thermal imidization temperatures on the solvent resistance and microscopic morphology of nanofiber substrates are also studied. The optimized monomers in this work contribute to a low-temperature imidization of PI nanofiber substrate. The solvent permeance of corresponding TFC OSN membrane with the insoluble PI nanofiber substrate reaches up to 11.2 L m −2 h −1 bar −1 with 99.7% rejection in rose bengal/DMF system, and good long-term stability. This work provides potential guidelines for developing next-generation OSN membranes under a green process. • Insoluble polyimide (PI) nanofibrous substrate was prepared facilely with low-temperature thermal imidization. • A green modification without toxic chemical solvent involved is applied. • PI nanofibrous substrate can withstand strong polar aprotic solvents for more than three months. • The high porosity and interconnected pores endow substrate superior solvent permeance. • TFC membrane exhibits outstanding OSN performance and long-term stability.

Aromatic Polyesters Containing Ether and a Kinked Aromatic Amide Structure in the Main Chain: Synthesis and Characterisation

A novel bisphenol containing preformed multiple ether and amide linkages, N, N′-Bis (4-hydroxyphenoxyphenylene) isophthalamide (IPCD), was prepared and analysed by spectroscopic methods. New aromatic polyesters were prepared by polycondensation of IPCD with 1, 3-benzene diacidchloride and/or 1, 4-benzene diacidchloride. These obtained polyesters were structurally analysed by infra-red spectroscopy, measurements of inherent viscosity, wide-angle X-ray diffraction patterns, and thermal techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and solubility tests in organic solvents. The synthesised polyesters had high molecular weights, as indicated by their inherent viscosities from 0.67 to 0.78 dL/g in N-methyl-2-pyrrolidone. The incorporation of ether and kinked aromatic amide moieties in the main polyester chains greatly affected the properties of these aromatic polyesters. The prepared polyesters readily dissolved in amide-type polar aprotic solvents and pyridine, indicating their solution processability. The DSC curves above the polyesters showed glass transition temperatures of 194 to 269 °C. TGA indicated that these newly obtained polyesters were stable up to 301 °C and retained a 39 to 48% weight at 900 °C. W-XRD analyses showed that the newly synthesised polyesters were amorphous, which is reflected in their solubility behaviour.

Effect of solvents and temperature on the structural, thermodynamic and electronic properties of capped phenylalanine: A computational study

Effects of solvents and temperature on the structural, thermodynamic, and electronic properties of L-configuration of N-acetyl-phenylalaninyl amide (NAPA) were studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approach. Enthalpy (H), entropy (S) and specific heat capacity (Cv) were found to increase with the increase of temperature (100 K-1600 K) because of the increasing intensities of molecular vibration. On the contrary, Gibb’s free energy (G) was found to decrease with the increase of temperature. The UV-light absorption maximum, λmax, is red-shifted in the presence of polar protic, aprotic and non-polar solvents. On the other hand, calculation shows that dipole moment in polar solvents (protic and aprotic), non-polar solvents, and the gas phase are ~3.35, ~3.0, and 2.5 D, respectively. However, no significant change was found in the HOMO-LUMO energy gap in the presence of different types of solvents. J. Bangladesh Acad. Sci. 45(2); 205-215: December 2021

Acid–base reaction of a super‐photoacid with a cooperative amide hydrogen‐bonded chain

AbstractThe excited‐state proton transfer (ESPT) of the strong photoacid, N‐methyl‐7‐hydroxyquinolium (NM7HQ+), was studied in the presence of N‐methylbenzamide (NMB) as a base in the aprotic polar solvent, acetonitrile. According to the Benesi–Hildebrand relation, it was revealed that the hydrogen (H)‐bonded complex of NM7HQ+ and NMB exists in the ground state in a 1:1 stoichiometry with the association constant of 22.2 ± 1.7 M−1. The fluorescence quenching of the 1:1 complex was observed to follow the Stern–Volmer relation with the molecularity of one for NMB indicating that the ESPT of NM7HQ+ occurs with the H‐bonded chain of two NMB molecules. Our study highlights the cooperative nature of H‐bonding in the chemical reactivity of amide in acid–base reactions as has already been reported for alcohol.

Designing Ionic Liquids as the Solvent for Efficient and Stable Perovskite Solar Cells.

As a green solvent, ionic liquids (ILs) are considered as a promising alternative to conventional polar aprotic solvents for the production of efficient and stable perovskite solar cells (PSCs). Moreover, with the use of IL solvents, perovskite films can be prepared without antisolvent treatments in an ambient environment instead of in a glovebox with inert gases, which simplifies the film manufacturing process and is favorable for industrialization production. However, the type of IL solvents that have been studied is limited, and the influence of IL molecular structures on the perovskite-film crystallization and device performance is not completely understood. In this work, four different ILs, methylammonium formate (MAF), methylammonium acetate (MAAc), methylammonium propionate (MAP), and mthylammonium isobutyrate (MAIB), are synthesized as the perovskite precursor solvents. The interaction between the functional groups of the synthesized solvents and Pb2+ in the precursor solution is studied, which has a direct impact on the morphology and crystallization of the deposited perovskite film. It is found that MAP solvent gives a high-quality perovskite film, which leads to the best photovoltaic performance with a champion PCE of 20.56% compared to the devices based on the other IL solvents. Moreover, the MAP-based device maintains 88% of its original PCE after 1000 h of storage in a N2 atmosphere, demonstrating excellent device stability. Therefore, it is concluded that MAP is the most suitable solvent for MAPbI3 films with respect to photovoltaic applications as compared to the other ILs.

Binary Solvent System Composed of Polar Protic and Polar Aprotic Solvents for Controlling the Dimensionality of MOFs in the Solvothermal Synthesis

The ample choice of organic ligand and series of available metal ions offer a library of metal–organic frameworks (MOFs) to be designed, synthesized, and applied for various interesting applications. However, the way to achieve complete control over the formation of desired architectures and properties is still an elusive goal. Several factors often directly or indirectly influence the synthesis of MOFs such as nature of solvent, pH, temperature, reactant stoichiometry, concentration of precursors, counterions, etc. These parameters are crucial for the formation of the crystalline product in the first place and also dictate the overall network dimension or topology. Herein, we have synthesized six Zn(II)/ Co(II)/ Cu(II) based MOFs and rationalized the effect of the presence of polar protic solvents like water/ethanol in directing the overall network dimension. The presence of polar protic solvents like ethanol/water resulted in the formation of secondary building units (SBUs) that directs the network to extend on a plane while the absence/scarcity of such solvents leads to a different SBU that facilitate propagation of the network in three dimensions. Such variation was attributed to the competitive coordination ability of such solvents and the extent of hydrogen bonding with the ligand.

In-situ growth of UiO-66-NH2 in porous polymeric substrates at room temperature for fabrication of mixed matrix membranes with fast molecular separation performance

In-situ growth of UiO-66-NH2 in ordinary porous polymeric substrates offers promising opportunities to eliminate interfacial defects in mixed matrix membranes (MMMs). However, this strategy is still hard to be realized because conventional hydrothermal synthesis of UiO-66-NH2 involves harsh conditions (e.g., high temperatures, and polar aprotic solvents), which are destructive to ordinary polymer. Herein, UiO-66-NH2 was in-situ grown in polymeric substrates under room temperature via a successive immersion of a porous polyether sulfones substrate in a Zr4+ formic acid/ethanol solution and a 2-aminoterephthalic acid ethanol/formic acid/water solution. Attenuated total refraction Fourier transform infrared and X-ray diffraction characterizations demonstrated the successful incorporation of UiO-66-NH2 in the substrate. The optimized membrane possessed a high pure water permeance of 209.5 L-2h−1 bar−1 and rejections higher than 99.5% towards small molecules of Congo Red, xylene brilliant cyanin G, and Rose Bengal sodium salt. More importantly, after a 5-day immersion in water or an intense ultrasonication treatment, the membrane showed no significant change in separation performance, suggesting its excellent stability. The novel strategy regarding MMMs with UiO-66-NH2in-situ growth disclosed in this study paves the way to develop advanced UiO-66-NH2 membranes toward sustainable molecular separation in environmental applications.

Amino-functionalized polysaccharide derivatives: Synthesis, properties and application

Polysaccharides, cellulose and chitin are fundamental structural biopolymers of our biome, they therefore demonstrate relatively high tensile strength compared to other biopolymers and great diversity. Aqueous insolubility is a natural requirement for these polymers to be fit for purpose. However, non-natural aminated polysaccharides, such as 6-deoxy-6-amino derivatives, display improved solubility profiles, thus allowing further modification in a wider range of protic and aprotic polar solvents. Improved aqueous solubility and additional charge density aids, among others, modest antimicrobial, antioxidant, anticancer and gene transfection properties. Cellulosic and chitinous feedstock is naturally abundant and ideal for further valorisation. However, limitations in environmentally desirable solvents and inconsistency in chemical processing are a key hurdle in the path to commercial exploitation of 6-deoxy-6-aminocellulose and 6-deoxy-6-aminochitosan. This review intents to highlight the successes and challenges in the chemical process methodology that influence optimal valorisation of cellulosic and chitinous waste in the context of exploiting waste derived biopolymers. Note that this review is focused on the synthesis of 6-deoxy-6-amino derivatives and not 6-O-linked aminated derivatives.

Insight into the dehydration of high-concentration fructose to 5-hydroxymethylfurfural in oxygen-containing polar aprotic solvents

A high 5-HMF yield of 85.4% was achieved in polar aprotic oxygen-containing solvent with strong electrophilic maleic acid by quenching DHH.

Solvent dielectric delimited nitro-nitrito photorearrangement in a perylenediimide derivative.

The discovery of vibrant excited-state dynamics and distinctive photochemistry has established nitrated polycyclic aromatic hydrocarbons as an exhilarating class of organic compounds. Herein, we report the atypical photorearrangement of nitro-perylenediimide (NO2-PDI) to nitrito-perylenediimide (ONO-PDI), triggered by visible-light excitation and giving rise to linkage isomers in the polar aprotic solvent acetonitrile. ONO-PDI has been isolated and unambiguously characterized using standard spectroscopic, spectrometric, and elemental composition techniques. Although nitritoaromatic compounds are conventionally considered to be crucial intermediates in the photodissociation of nitroaromatics, experimental evidence for this has not been observed heretofore. Ultrafast transient absorption spectroscopy combined with computational investigations revealed the prominence of a conformationally relaxed singlet excited-state (SCR1) of NO2-PDI in the photoisomerization pathway. Theoretical transition state (TS) analysis indicated the presence of a six-membered cyclic TS, which is pivotal in connecting the SCR1 state to the photoproduct state. This article addresses prevailing knowledge gaps in the field of organic linkage isomers and provides a comprehensive understanding of the unprecedented photoisomerization mechanism operating in the case of NO2-PDI.

Dissolution behavior of cellulose in a novel cellulose solvent

We have found that cellulose can be dissolved rapidly in the mixed solvent of tetrabutylammonium acetate (TBAA) and a polar aprotic solvents (PAS) at 50 °C and the obtained cellulose solution could be regenerated into cellulose film and fiber. The factors affecting the dissolution behavior of cellulose were investigated and it was found that the solubility and dissolution rate of cellulose in the mixed solvent are significantly dependent on the species of PAS and the molar ratio of PAS/TBAA. The suitable PAS are dimethyl sulfoxide, pyridine, dimethylacetamide, dimethylformamide and N-Methyl-2-pyrrolidone, and dimethyl sulfoxide is the best one in regard to the solubility and dissolution rate of cellulose. The optimal molar ratio of PAS/TBAA was determined by DN of the polar aprotic solvents. The dissolution behaviour of cellulose in the mixed solvent was proposed to involve the solvent diffusion, solvation of TBA+ as well as disruption of the intermolecular or intramolecular hydrogen bonds of cellulose.

Facile biodegradation of N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone by source-derived Bacillus strain APS1 for water reclamation and reuse

Large volume of hazardous aprotic polar solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) are released to the environment through wastewater stream, generated from industries which include polymer membrane industries. Biodegradation of these solvents by bacterial strains is a convenient process but inherent toxicity of these solvents at high concentrations often limits the efficiency of the process. Current work reports a facile biodegradation of DMF, DMAc and NMP at high concentrations employing free cells of Bacillus cereus APS1 strain, isolated from DMF rich wastewater. The newly isolated strain is capable of degrading these solvents utilizing them as sole carbon and nitrogen source. The free cells of APS1 are highly tolerant to DMF concentration as high as 35000 mg/L. Biodegradation of solvents is monitored by refractive index, HPLC and 1H NMR spectroscopy. Effect of pH of the wastewater, cell growth and concentration of the solvents is evaluated. Almost complete biodegradation of DMF(30000 mg/L) present in wastewater occurs within 48 h, while 192 h is required at DMF concentration of 35000 mg/L. Time required for complete biodegradation of DMAc and NMP at concentration of 10000 mg/L is 72 h and 96 h respectively. In batch mode, the biodegradation efficacy of APS1 remains steady for multiple cycles. Ultrafiltration membranes prepared using reclaimed water and fresh water as nonsolvents show similar morphology and performance. This work shows that a strain isolated from DMF wastewater is advantageous for the biodegradation of DMF or similar kind of amide containing solvents.