Benign Solvent Research Articles

Spirobifluorene-based non-fullerene acceptors for the environmentally benign process

Spirobifluorene based non-fullerene acceptors (NFAs) having meta-ethylhexyl oxy (m-OEh) substituents (PBDB-T: spiro-bridged NFAs) were synthesized. The orthogonal molecular structure of the m-OEh-substituted spirobifluorene with different end groups provided high solubility and kept the stable morphology between donor-acceptor. Organic Photovoltaic (OPV) device performance was not significantly affected by switching the processing solvent from a chlorinated solvent to an environmentally benign solvent, because suitable morphology and crystallinity were retained. The ITO/ZnO/PBDB-T:spiro-bridged NFA/MoOx/Ag OPV devices prepared using a chlorobenzene as the processing solvent displayed maximum efficiency in the range of 6.44–5.78%, while the devices made using xylene as the processing solvent had a lower maximum efficiency ranging from 6.14–4.66%. The OPV performance of the devices made using chlorobenzene decreased in the order of sp-mOEh-ITIC > sp-mOEh-ITIC-M > sp-mOEh-ITIC-F > sp-mOEh-ITIC-Cl because an electron donating end group increased open-circuit voltage (Voc), while the electron withdrawing end group increased the short-circuit current density (Jsc). Although the OPV performance of the four spiro-bridged derivatives by xylene was showed to be similar order of that by chlorobenzene solvent processing, the efficiency drop from chlorobenzene solvent to xylene solvent showed following order sp-mOEh-ITIC < sp-mOEh-ITIC-M < sp-mOEh-ITIC-F < sp-mOEh-ITIC-Cl, which depended on the polarity effect of end groups.

Lignin-First Fractionation of Softwood Lignocellulose Using a Mild Dimethyl Carbonate and Ethylene Glycol Organosolv Process.

A mild lignin-first acidolysis process (140 °C, 40 min) was developed using the benign solvent dimethyl carbonate (DMC) and ethylene glycol (EG) as a stabilization agent/solvent to produce a high yield of aromatic monophenols directly from softwood lignocellulose (pine, spruce, cedar, and Douglas fir) with a depolymerization efficiency of 77-98 %. Under the optimized conditions (140 °C, 40 min, 400 wt % EG and 2 wt % H2 SO4 to pinewood), up to 9 wt % of the aromatic monophenol was produced, reaching a degree of delignification in pinewood of 77 %. Cellulose was also preserved, as evidenced by a 85 % glucose yield after enzymatic digestion. An in-depth analysis of the depolymerization oil was conducted by using GC-MS, HPLC, 2 D-NMR, and size-exclusion chromatography, which provided structural insights into lignin-derived dimers and oligomers and the composition of the sugars and derived molecules. Mass balance evaluation was performed.

Moldable Crystalline α-Chitin Hydrogel with Toughness and Transparency toward Ocular Applications

A N-acetylated chitosan hydrogel was investigated for ocular applications. One of the drawbacks in the original hydrogel protocol, poor moldability, was circumvented by optimizing the addition of the acetylating agent, acetic acid anhydride (Ac2O), at −10 °C. This simple but significant optimization realized the preparation of N-acetylated chitosan hydrogels with a wider variety of parameters such as higher chitosan concentration and molecular weight, the use of a more benign solvent (ethanol replaced methanol), and the arbitral shapes ranging from microbeads and contact lenses to bulky blocks that could be gripped. The prepared N-acetylated chitosan hydrogels exhibited high transparency and integrity given the nanofibrous network made of highly crystalline α-chitin. Furthermore, the gel retained a regenerable character: an oven-dried gel was reswollen by emersion in an acid bath. These previously unnoticed advantages and the innate high biocompatibility of chitosan and chitin elevate N-acetylated chitosan hydrogel as a next-generation bio-derived soft material for ocular applications such as contact lenses, artificial corneas, and drug delivery vehicles.

Expeditious Green Synthesis of Novel 4-Methyl-1,2,5,6-tetraazafluoranthen-3(2H)-one Analogue from Ninhydrin: N/S-Alkylation and Aza-Michael Addition.

A straightforward green synthesis of 4-methyl-1,2,5,6-tetraazafluoranthen-3(2H)-one 6 is reported from ninhydrin 1 via condensation with ethyl acetoacetate, followed by cyclization with hydrazine hydrate in water as a benign solvent. Tetraazafluoranthen-3-thione 7 was obtained using Lawesson’s reagent. N-alkylated tetraazafluoranthen-3-one 8–12 and S-alkylated analogues 13–15 were synthesized via alkylation. The investigation of the unique reactivity of 4-methyl-1,2,5,6-tetraazafluoranthen-3(2H)-one/thione toward the alkylation and aza-Michael additions was explored.

Comparison of acidic deep eutectic solvents in production of chitin nanocrystals

Five different acidic deep eutectic solvents (DESs) composed of choline chloride and organic acids were applied to fabricate chitin nanocrystals (ChNCs). All DESs resulted in high transmittance and stable ChNCs suspensions with very high mass yield ranging from 78 % to 87.5 % under proper reaction conditions. The acidic DESs had a dual role in ChNCs fabrication, i.e. they promoted hydrolysis of chitin and acted as an acylation reagent. Physicochemical characterization of chitin revealed that the removal of amorphous area during DES treatments led to increased crystallinity of ChNCs and a dimension diversity correlated the DES used. The average diameter and length of individual ChNCs ranged from 42 nm to 49 nm and from 257 nm to 670 nm, respectively. The thermal stability of ChNCs was comparable to that of pristine chitin. Thus, acidic DESs showed to be non-toxic and environmentally benign solvents for production of functionalized chitin nanocrystals.

An Environment-Friendly Method for Green Synthesis of Pyranopyrazole Derivatives Catalyzed by CoCuFe2O4 Magnetic Nanocrystals under Solvent-Free Conditions

An efficient and rapid four component reaction of ethyl acetoacetate, hydrazine hydrate, malononitrile and different aldehydes at environmentally benign room temperature and solvent free conditions. This research has developed for synthesis of pyranopyrazole derivatives in the presence of CoCuFe2O4 magnetic nanocrystals as reusable catalyst. The catalyst prepared and characterized by FT-IR, XRD, SEM, EDX and VSM techniques. The products confirmed by spectroscopic and physical data such as; melting points, FT-IR and 1H NMR analyses.

Ultrasonic preparation and nanosheets supported binary metal oxide nanocomposite for the effective application towards the electrochemical sensor.

Binary metal oxides (La2O3@SnO2) decorated reduced graphene oxide nanocomposite was synthesized by ultrasound process in an environmentally benign solvent with a working frequency of 25 and 40kHz (6.5l200 H, Dakshin, India and maximum input power 210W). Further, to enhance the electrocatalytic activity, the reduced graphene oxide (rGO) was prepared from graphene oxide by ultrasonication method. As prepared La2O3@SnO2/rGO was scrutinized using XRD, TEM, EDX and quantitative test for the structural and morphology properties. As modified La2O3@SnO2/rGO nanocomposite exhibits better electrochemical activity towards the oxidation of methyl nicotinate with higher anodic current compared to other modified and unmodified electrode for the detection of methyl nicotinate with larger linear range (0.035-522.9µM) and lower limit of detection (0.0197µM). In addition, the practical feasibility of the sensor was inspected with biological samples, reveals the acceptable recovery of the sensor in real samples.

Polycaprolactone Electrospun Fiber Mats Prepared Using Benign Solvents: Blending with Copper(II)-Chitosan Increases the Secretion of Vascular Endothelial Growth Factor in a Bone Marrow Stromal Cell Line.

Inducing the formation of new blood vessels (angiogenesis) is an essential requirement for successful tissue engineering. Approaches have been proposed to enhance angiogenesis using growth factors and other biomolecules; however, this approaches present drawbacks in terms of high cost and patient safety. Copper is known to effectively regulate angiogenesis and can offer a more cost-effective alternative than the direct use of growth factors. With this study, a strategy to incorporate copper in electrospun fibrous scaffolds with pro-angiogenic properties is presented. Polycaprolactone (PCL) and copper(II)-chitosan are electrospun using benign solvents. The morphological and physicochemical properties of the fiber mats are investigated through scanning electron microscopy (SEM), static contact angle measurements, energy dispersive X-ray, and Fourier-transform infrared spectroscopies. Scaffold stability in phosphate buffered saline at 37 °C is monitored over 1 week. A bone marrow stromal cell line (ST-2) is cultured for 7 days and its behavior is evaluated using SEM, fluorescence microscopy and a tetrazolium salt-based colorimetric assay. Results confirm that PCL/copper(II)-chitosan is suitable for electrospinning. The fiber mats are biocompatible and favor cell colonization and infiltration. Most notably, the angiogenic potential of PCL/copper(II)-chitosan blends is confirmed by a three-fold increase in VEGF secretion by ST-2 cells in the presence of copper(II)-chitosan.

Sterically driven metal-free oxidation of 2,7-di-tert-butylpyrene

A new metal-free ortho oxidation of 2,7-di-tert-butylpyrene provides in high yield the corresponding 4,5-dione and 4,5,9,10-tetraone in environmentally benign solvents.

Accessible and sustainable Cu(0)-mediated radical polymerisation for the functionalisation of surfaces

Towards use of environmentally benign solvents and ambient conditions for surface functionalisation by controlled growth of thick cationic polymer brushes.

Ni nanoparticle-confined covalent organic polymer directed diaryl-selenides synthesis.

The present work describes the preparation of a new covalent organic polymer (COP) and its application as a hetero support for diaryl selenides synthesis. A nitrogen rich COP (CGP) has been synthesized via SNAr reaction of cyanuric chloride with guanidinium hydrochloride. The successful confinement of COP with Ni nanoparticles through post-synthetic transformations (Ni@CGP) provides excellent catalytic activity for the transformation of aryl halides into diaryl selenides using elemental selenium powder. The synthetic transformations are well confirmed using various modern analytical and spectroscopic techniques which reveal high chemical and thermal durability. The N-rich framework of CGP fortifies the confinement of Ni NPs. Ni@CGP provides an efficient approach for diaryl selenides synthesis using a very cheap selenating reagent under water benign solvent conditions (DMSO : H2O) at room temperature with high reusability. Significantly, our work not only contributes the opportunity for developing economical and effective non-noble metal decorated COPs as heterogeneous catalysts, but also delivers an efficient approach to produce industrially important C-Se coupling products.

Neat Ionic liquid and α-Chymotrypsin-Polymer Surfactant Conjugate-Based Biocatalytic Solvent.

Performing biocatalysis in nonaqueous solvents is advantageous as it imparts enhanced solubility to hydrophobic substrates and an ability to increase the temperature for shifting reaction equilibrium in the forward direction. In this work, we show the design and development of another class of nonaqueous composite solvent obtained by mixing surface modified enzyme and neat ionic liquid (IL). We systematically probe the interaction and solubility of industrially relevant α-chymotrypsin in its native or surface-bound polymer-surfactant bioconjugated form, with neat protic (N-methyl-2-pyrrolidonium trifluoromethanesulfonate; [NMP][OTf]), or aprotic (1-methyl-3-(4-sulfobutyl)-1H-imidazol-3-ium trifluoromethanesulfonate; [HO3S(CH2)4MIm][OTf]), ILs. Polarized optical micrographs show that the lyophilized powder of native α-chymotrypsin, nCT, does not disperse in either of the neat ILs, however, its polymer surfactant (PS)-coated bioconjugate counterparts, PScCT, in the waterless state, can be well-dispersed and solubilized in the neat [HO3S(CH2)4MIm][OTf]. The solubilization of waterless bioconjugates of PScCT in neat aprotic IL provides a composite liquid, WL-ImPScCT (WL: waterless, Im: [HO3S(CH2)4MIm][OTf]), having a viscosity of 69.6 Pa·s at 25 °C with a shear-thinning behavior, ≈ 15 w/w % α-chymotrypsin, and ≈ 1.2 w/w % residual water content. Detailed secondary structural analysis using circular dichroism and Fourier self-deconvolution on the ATR-FTIR data of WL-ImPScCT liquid reveals retention of the near native secondary structure of α-chymotrypsin. Further, using a combination of fluorescence spectroscopy and electron spray ionization mass spectrometry, we show that scattering of dry and powdered bovine serum albumin (BSA) protein on the WL-ImPScCT composite liquid results in the solubilization of the former, followed by limited proteolysis of BSA by the α-chymotrypsin. Our results, therefore, show the stabilization of α-chymotrypsin in a neat aprotic IL environment to yield a composite liquid, which not only acts as a nonaqueous, nonvolatile, and environmentally benign solvent, but also provides a biocatalytic platform capable of carrying out reactions relevant for biotransformations, food processing, drug delivery, and various other applications.

Lewis acid–catalyzed green synthesis and biological studies of pyrrolo[3,4‐c]pyrazoles in aqueous medium

AbstractAn environmentally benign approach in aqueous medium by means of Lewis acid catalyst affords a wide spectrum of pyrazoline derivatives in satisfactory yields. [3+2] cycloaddition reactions of substituted azomethine‐N‐imines to maleimide in aqueous medium at relatively high concentrations of Lewis acid catalyst have emerged as an environment friendly alternative to conventional solvents. Promising catalytic activity has been revealed by Lewis acid like Cu (NO3)2 in aqueous medium. The obvious features of this synthetic protocol were short reaction time, high efficiency, less hazardous synthesis by benign solvent, catalysis, modest workup, and a clean reaction methodology.

Processing Strategies for an Organic Photovoltaic Module with over 10% Efficiency

Summary A series of readily accessible and scalable benzo[1,2-b:4,5-b′]dithiophene (BDT)-2,5-dithienyl-thieno[3,4-c]pyrrole-4,6-dione (TPD-T2)-based donor polymers are utilized in organic photovoltaic (OPV) cells blended with the non-fullerene acceptor IT-4F. All polymers readily dissolve in chlorine-free solvents such as xylene, and the corresponding photoactive blend films can be processed in ambient from this solvent to fabricate cells with power conversion efficiencies (PCEs) >12%–14%. Furthermore, the blend processing and OPV metrics are remarkably insensitive to the processing methodology (spin coating versus blade coating), processing solvent, polymer molecular mass and dispersity index, and the results were rationalized by UV-vis, PL, fsTA, AFM, TEM, GIWAXS, and SCLC measurements. These properties enable the first OPV modules, processed in ambient from a benign solvent, with a certified PCE of 10.1% for an area of 20.4 cm2 and >7% after light soaking. The same module also delivers a power of ∼40 μW/cm2 (PCE ∼22%) under indoor lighting.

Polyvinylpyrrolidone - Reduced Graphene Oxide - Pd Nanoparticles as an Efficient Nanocomposite for Catalysis Applications in Cross-Coupling Reactions

This paper reported a scientific approach adopting microwave-assisted synthesis as a synthetic route for preparing highly active palladium nanoparticles stabilized by polyvinylpyrrolidone (Pd/PVP) and supported on reduced Graphene oxide (rGO) as a highly active catalyst used for Suzuki, Heck, and Sonogashira cross coupling reactions with remarkable turnover number (6500) and turnover frequency of 78000 h-1. Pd/PVP nanoparticles supported on reduced Graphene oxide nanosheets (Pd-PVP/rGO) showed an outstanding performance through high catalytic activity towards cross coupling reactions. A simple, reproducible, and reliable method was used to prepare this efficient catalyst using microwave irradiation synthetic conditions. The synthesis approach requires simultaneous reduction of palladium and in the presence of Gaphene oxide (GO) nanosheets using ethylene glycol as a solvent and also as a strong reducing agent. The highly active and recyclable catalyst has so many advantages including the use of mild reaction conditions, short reaction times in an environmentally benign solvent system. Moreover, the prepared catalyst could be recycled for up to five times with nearly the same high catalytic activity. Furthermore, the high catalytic activity and recyclability of the prepared catalyst are due to the strong catalyst-support interaction. The defect sites in the reduced Graphene oxide (rGO) act as nucleation centers that enable anchoring of both Pd/PVP nanoparticles and hence, minimize the possibility of agglomeration which leads to a severe decrease in the catalytic activity.

Synthesis of Sulfonylisoureas via Sulfo-Click Reactions

The synthesis of sulfonylisoureas from thiocarbamates and sulfonyl azides via a new variant of the sulfo-click reaction is reported. Water was found to be the environmentally benign solvent of choice over various other solvents tested, and the use of any additives was not required to obtain complete conversion. The experimentally simple reaction­ tolerates a broad range of electron-donating and electron-withdrawing substituents attached on both the thiocarbamate and the sulfonyl azide, as shown with the synthesis of 27 sulfonylisoureas that were prepared in yields ranging from 34% to 78%.

Kinetic analysis of the complete mechanochemical synthesis of a palladium(II) carbene complex

Benzimidazoline-2-ylidene complexes of palladium(II) were synthesized mechanochemically in a vibratory ball mill. Complete syntheses began with preparation of benzimidiazolium halides from commercially available starting materials. These “greener chemistry” syntheses proceed in high yield and require minimal purification using environmentally benign solvents. Kinetic analysis shows that liquid assisted grinding impedes the production to benzimidazolium halides while enhancing the production of the palladium-carbene complex.

Recent Advances of Using Ionic Liquids for Biopolymer Extraction and Processing.

The evolution of petroleum-derived polymers is one of the crowning accomplishments of the past century. Although the significant economic gains from this industrial model of resource utilization are achieved, the environmental impacts are fatal. One of the principles of sustainable development is to replace such polymers with potential alternatives derived from renewable materials. Biopolymers derived from natural resources afford a new, versatile, environmentally benign feedstock that could exhibit closed-loop life cycles as part of a future material's industrial ecology. However, the solubility and processability of biopolymer materials provoke a serious bottleneck owing to their dense networks of inter - and intramolecular bondings and structural heterogeneity. Recently, ionic liquids (ILs) have emerged as promising green solvents and acquired augmented appreciation for their peerless power of biopolymer processing. Among the fourteen principle of green chemistry, the two key elements encourage the exploitation of renewable raw materials by using environmentally benign solvents that cover in dissolution of biopolymers using ILs. This mini review represents a brief overview of the comprehensive ILs assisted extraction and processing of various biopolymeric materials for value-added applications.

Organic/Inorganic Heterogeneous Silica‐Based Photoredox Catalyst for Aza‐Henry Reactions

The transformation of light into chemical energy is a leitmotiv in the development of sustainable and environmentally concerned chemical processes. Chemists invented original concepts to address this purpose, like photoredox catalysis, which became a wonderful tool to transform simple organic compounds into high‐value products. Nevertheless, the most relevant transition metal based photocatalysts suffer from major disadvantages like toxicity, cost, and poor recyclability potential. To circumvent this, we propose a new generation of heterogeneous photoredox catalysts resulting from the combination of porous silica materials and Rose Bengal. They promote carbon–carbon bond formations under visible‐light in environmentally benign solvent using air as the only stoichiometric redox partner. The pure covalent photocatalytic system provides a robust and recyclable system for greener catalysis. This report would be of broad significance because it addresses important sustainability issues: recycling, non‐toxic metal‐free photocatalysts, and less‐waste‐producing chemical process.

Identification and Characterization of Methyl Isoeugenol Compound from the Golden Yellow Hued Muga Silk Fiber of India

ABSTRACT Organic extraction of pigmentation constituents of the cocoons of Antheraea assamensis (muga) was investigated in this study. Chemical extraction of muga cocoon fibers and their host plant som (Machilus bombycina) leaves were carried out using two benign solvents: hexane and ethyl acetate. Thin-layer chromatography (TLC) revealed the presence of methyl isoeugenol and isoeugenyl acetate from extracts of cocoon fiber and som leaves, respectively. The compounds were further confirmed by gas chromatography-mass spectroscopy (GC-MS) and nuclear magnetic resonance (NMR) analysis. Methyl isoeugenol is a yellow colored compound, which resembles the color of the muga fiber and may be responsible for coloration of the same. It is anticipated that isoeugenyl acetate (also known as isoeugenol acetate), a phenylpropanoid compound present in the host plant might be converted to methyl isoeugenol during the course of metabolism in the silkworm larva, which in turn may be responsible for production of golden yellow colored silk fiber for building the cocoons. The present investigation might help to utilize methyl isoeugenol as a potential dyeing material for other fabrics in the industry thus providing a new dimension into the textile field.