Aromatic Solvents Research Articles

Stereochemical Behavior of Pyrrolo-Pyrazole Peptidomimetics Promoting Phase-Selective Supramolecular Organogels.

Supramolecular gels were developed by taking advantage of an assembly of small dipeptides containing pyrrolo-pyrazole scaffolds. The dipeptides were prepared through a robust and ecofriendly synthetic approach from the commercially available starting materials of diazoalkanes and maleimides. By playing with the functionalization of the scaffold, the choice of the natural amino acid, and the stereochemistry, we were able to obtain phase-selective gels. In particular, one peptidomimetic showed gelation ability and thermoreversibility in aromatic solvents at very low concentrations. Rheology tests showed a typical viscoelastic solid profile, indicating the formation of strong gels that were stable under high mechanical deformation. NMR studies were performed, allowing us to determine the conformational and stereochemical features at the base of the supramolecular interactions.

Do Electrostatics Control the Diffusive Dynamics of Solitary Water? NMR and MD Studies of Water Translation and Rotation in Dipolar and Ionic Solvents.

NMR-based measurements of the diffusion coefficients and rotation times of solitary water and benzene at 300 K are reported in a diverse collection of 13 conventional organic solvents and 10 imidazolium ionic liquids. Proton chemical shifts of water are found to be correlated to water OH-stretching frequencies, confirming the importance of electrostatic interactions in these shifts. However, the influence of magnetic interactions in aromatic solvents renders chemical shifts a less reliable indicator of electrostatics. Diffusion coefficients (DB) and rotational correlation times (τB) of benzene in the solvents examined are accurately described as functions of viscosity (η) by DB ∝ η-0.81 and τB ∝ η0.64. Literature values of DB and τB in alkane and normal alcohols, which were not included among the solvents studied here, are systematically faster than predicted by these correlations, indicating that factors beyond solvent viscosity play a role in determining the friction on benzene. In contrast to benzene, water diffusion and rotation are poorly described in terms of viscosity alone, even in the dipolar and ionic solvents measured here. The present data and the substantial literature data already available on dilute water diffusion show a systematic dependence of DW on solvent polarity among isoviscous solvents. The aspect of solvent polarity most relevant to water dynamics is the ability of a solvent to accept hydrogen bonds from water, as conveniently quantified by the frequency of water's OH stretching band, ΔνOH. The friction on translation, ζtr = kBT/DW, and rotation, ζrot = kBTτW, are both well correlated by functions of the form ζ(η, ΔνOH) = a1ηa2 exp (a3ΔνOH), where the ai are adjustable parameters. Molecular dynamics simulations reveal a strong coupling between electrostatic and nonelectrostatic water-solvent interactions, which makes it impossible to dissect the friction on water into additive dielectric and hydrodynamic components. Simulations also provide a tentative explanation for the unusual form of the correlating function ζ(η, ΔνOH), at least in the case of ζrot.

Theoretical analysis of hydrogen solubility in direct coal liquefaction solvents

The cyclic hydrogenation technology in a direct coal liquefaction process relies on the dissolved hydrogen of the solvent or oil participating in the hydrogenation reaction. Thus, a theoretical basis for process optimization and reactor design can be established by analyzing the solubility of hydrogen in liquefaction solvents. Experimental studies of hydrogen solubility in liquefaction solvents are challenging due to harsh reaction conditions and complex solvent compositions. In this study, the composition and content of liquefied solvents were analyzed. As model compounds, hexadecane, toluene, naphthalene, tetrahydronaphthalene, and phenanthrene were chosen to represent the liquefied solvents in chain alkanes and monocyclic, bicyclic, and tricyclic aromatic hydrocarbons. The solubility of hydrogen X (mol/mol) in pure solvent components and mixed solvents (alkanes and aromatics mixed in proportion to the chain alkanes + bicyclic aromatic hydrocarbons, bicyclic saturated aromatic hydrocarbons + bicyclic aromatic hydrocarbons, and bicyclic aromatic hydrocarbons + compounds containing heteroatoms composed of mixed components) are determined using Aspen simulation at temperature and pressure conditions of 373–523 K and 2–10 MPa. The results demonstrated that at high temperatures and pressures, the solubility of hydrogen in the solvent increases with the increase in temperature and pressure, with the pressure having a greater impact. Furthermore, the results revealed that hydrogen is more soluble in straight-chain alkanes than in other solvents, and the solubility of eicosanoids reaches a maximum of 0.296. The hydrogen solubility in aromatic ring compounds decreased gradually with an increase in the aromatic ring number. The influence of chain alkanes on the solubility of hydrogen predominates in a mixture of solvents with different mixing ratios of chain alkanes and aromatic hydrocarbons. The solubility of hydrogen in mixed aromatic solvents is less than that in the corresponding single solvents. Hydrogen is less soluble in solvent compounds containing heteroatoms than in compounds without heteroatoms.

A Systematic Investigation of the Kinetic Models Applied to the Transport Behaviors of Aromatic Solvents in Unfilled Hydrogenated Nitrile Rubber/Ethylene Propylene Diene Monomer Composites.

Kinetic models of solvent transport behaviors are widely used in rubber-solvent systems, and some key points are still worthy of attention. In this work, the Korsmeyer-Peppas and Peppas-Sahlin models were chosen to fit the transport behaviors of three aromatic solvents, benzene, toluene and p-xylene, in the hydrogenated nitrile rubber (HNBR)/ethylene propylene diene monomer (EPDM)-based vulcanizates. The different effects of the various selected transport times (ti) used for fitting on the results of the mathematical models were compared. Moreover, a method to obtain the n parameter for the Korsmeyer-Peppas model and the m parameter for the Peppas-Sahlin model at ti = 0 was discussed. It was found that the differences in values of ti greatly influenced the impact on the fitting results of all the parameters for the two models. In addition, the n parameter for the Korsmeyer-Peppas model along with the m parameter for the Peppas-Sahlin model, which can characterize the transport mechanism, showed differing applicability. But the n and m parameters at ti = 0 obtained by linear fitting showed similar rules with some differences in values. These discussions give important guidance for the application of kinetic transport models in rubber-solvent systems.

Poly(styrene-co-1-octene) behavioral differences in aliphatic and aromatic solvents: molecular dynamics simulation and DFT-D quantum calculations

Copolymerizing aromatic and aliphatic comonomers helps to create efficient superabsorbents to remove oil from seawater. In this work, the best sequence of styrene and 1-octene at different 1-octene molar percentages (x) was found for poly(styrene-r−1-octene) (CP-x) using neural network potential. According to the calculated characteristics of CP-x using molecular dynamics simulation, increasing the x amount up to 6% in the chain aromatic structure caused the chain expansion by ∼ 20% and the reduction of its diffusion coefficient in n-heptane by ∼ 70%. The determined Helmholtz free energy via thermodynamic integration formula showed a decrease from −2762.7 to −3818.3 kcal mol−1 (∼ 38% reduction) and entropy changes illustrated an increase from 5.12 to 8.21 kcal mol−1.K (∼ 60% increase) indicating a partial conversion of the copolymer nature from aromatic to aliphatic with raising x. This issue led to a ∼ 15% enhancement in the interaction energy between the chain and solvent media meaning a better tendency to n-heptane and the increment of the interfacial density of the solvent molecules around the copolymer chain with higher x. The quantum calculations also proved that toluene with the chain styrene ring, and n-heptane with the chain 1-octene have created a parallel orientation, due to the charge transfer energy arising from an occupied C-H bonding orbital to an adjacent one. This phenomenon moved the electron density to the boundary area between them and changed the chain conformation in the media. Compression of the CP-x characteristics in n-heptane and toluene unmasked the contrariwise behaviors of the copolymer in aliphatic and aromatic solvents, except CP-4, which is the best candidate to use in the oil absorption from water surfaces. The performed theoretical investigation of the CP-x has revealed the hidden molecular insights into the copolymer chain which can help experimentalists reduce their trial and error to manufacture efficient supper oil absorbents.

Direct lithium extraction from spent batteries for efficient lithium recycling

The flourishing expansion of the lithium-ion batteries (LIBs) market has led to a surge in the demand for lithium resources. Developing efficient recycling technologies for imminent large-scale retired LIBs can significantly facilitate the sustainable utilization of lithium resources. Here, we successfully extract active lithium from spent LIBs through a simple, efficient, and low-energy-consumption chemical leaching process at room temperature, using a solution comprised of polycyclic aromatic hydrocarbons and ether solvents. The mechanism of lithium extraction is elucidated by clarifying the relationship between the redox potential and extraction efficiency. More importantly, the reclaimed active lithium is directly employed to fabricate LiFePO4 cathode with performance comparable to commercial materials. When implemented in 56 Ah prismatic cells, the cells deliver stable cycling properties with a capacity retention of ∼90% after 1200 cycles. Compared with the other strategies, this technical approach shows superior economic benefits and practical promise. It is anticipated that this method may redefine the recycling paradigm for retired LIBs and drive the sustainable development of industries.

Rapid coating of millimeter‐scale hydrogel capsules with interfacial polymerization

AbstractA rapid and mild coating strategy was applied on the millimeter scale calcium alginate capsules (Ca‐SA caps) by in situ interfacial polymerization of ethyl cyanoacrylate (ECA). The generated poly(ethyl cyanoacrylate) (PECA) coating was initiated by trace water in the surface of the Ca‐SA caps. The effects of ECA content, reaction time, and type of aromatic solvent on the morphology and control‐release property of the resulting PECA‐coated Ca‐SA caps (Ca‐SA caps@PECA) were investigated. The results demonstrated a white PECA layer successfully coated on the surface of Ca‐SA caps. Notably, the Ca‐SA caps@PECA remained consistently pleasing spherical shape as prepared in methylbenzene and ethylbenzene. When the ECA was 6 mL, the thickness of PECA layer of the Ca‐SA caps@PECA was 43.52 μm. Compared with the Ca‐SA caps, the weight retention ratio of water in the Ca‐SA caps@PECA increased by 254.61%, indicating the effective delay of water diffusion from core of the Ca‐SA caps@PECA. Moreover, the PECA coating improved the stability of the Ca‐SA caps@PECA, which achieved release‐controlling of dye at different pH. This method provides solution for surface modification of fragile hydrogel capsules to effectively control the releasing of liquid core, which is highly valuable in the field of food, cosmetic, and medical delivery.

Multistimuli-responsive diaryldibenzofulvene derivatives and fluorescent detection of volatile organic vapors

Through molecule design, the aromatic fused ring groups (naphthyl and anthracyl) were introduced into 9-benzylidene-9H-fluorene to prepare the diaryldibenzofulvene derivatives with asymmetric structures, which exhibited typical aggregation induced emission (AIE) behavior. To multiple stimuli such as grinding, solvent fuming, and heating, the anthracene-based compound (9-(anthracen-9-yl(phenyl)methylene)-9H-fluorene) powders displayed high contrast fluorescence response behavior, whose emission could convert among yellow (570 nm), yellow green (560 nm), green (526 nm), and cyan (478 nm). Meanwhile, four single crystals of the anthracene-based compound were obtained from different conditions, exhibiting polymorphism phenomena. Through the XRD patterns and the data of the monocrystalline analysis, the different fluorescent emissions originated from changes in the molecular packing. Based on this, two fluorescent detection papers (A) and (B) were prepared using the anthracene-based compound in different solvents. The detection paper showed significant fluorescence quenching for THF and obvious fluorescence enhancement for aromatic solvents. Based on changes in fluorescence intensity and emission wavelength, various volatile organic vapors could be detected accurately by using both detection papers simultaneously. Therefore, this multi stimulus responsive fluorescent compound has potential applications in detection, recognition, sensing and other fields.

Playing with Protic Additives to Improve the Outcome of Rhodium‐Catalyzed Hydroarylation of Fullerene C60 with Arylboronic Acids

AbstractA new one‐phase process for hydroarylation of C60 fullerene using arylboronic acids and a rhodium catalyst in an aromatic solvent containing soluble protic additives is described. Yields of monohydroarylated product with tert‐butanol and water as the protic additive range from 14 to 50 % depending on which arylboronic acid is used after reaction times of 4 hours or less which is a significant improvement from the outcome of reactions carried out using conditions from the literature. Accurate monitoring of reaction outcomes was achieved by a combination of UV‐Vis spectroscopy and 1H‐NMR spectroscopy: C60 conversion was determined using an analytical HPLC‐UV‐vis method employing commonly available columns for the separation, while product formation was quantified by 1H‐NMR spectroscopy with an internal standard. Moreover, two new arylboronic acids carrying 4‐alkynyl aryl substituents, synthesized using Sonogashira couplings, are reported, as well as the use of these in the hydroarylation of C60.

Synthesis of Ultra-High-Molecular-Weight Polyethylene by Transition-Metal-Catalyzed Precipitation Polymerization.

Ultra-high-molecular-weight polyethylene (UHMWPE) plays an important role in many important fields as engineering plastics. In this contribution, a precipitation polymerization strategy is developed by combination of highly active phosphino-phenolate nickel catalysts with polymer-insoluble solvent (heptane) to access UHMWPE (M n up to 8.3 × 106 g mol-1) with good product morphology, free-flowing characteristics, and great mechanical properties. Compared with the academically commonly used aromatic solvent (toluene), the utilization of heptane offers simultaneous enhancement in important parameters including activity, polymer molecular weight, and catalyst thermal stability. This system can also generate polar functionalized UHMWPE with molecular weight of up to 1.6 × 106 g mol-1 in the copolymerization of ethylene with polar comonomers. More importantly, this precipitation polymerization strategy is generally applicable to several representative transition metal catalyst systems, leading to UHMWPE synthesis with good product morphology control.

Highly solvent-dependent naphthalene diimide-based fluorescent polymer sensors for detecting p-xylene

P-xylene (PX), as one of xylenes, is a kind of very important chemical raw material. It is generally fabricated using methanol (MeOH) and toluene (TOL), and serves as a useful intermediary. However, it is difficult to use a simple and convenient tool to distinguish it from TOL and MeOH. Herein, we reported a simple naphthalene diimide-based polycaprolactone polymer (NDI-PCL) as a high-sensitive fluorescent sensor for xylene detection from MeOH and TOL. NDI-PCL was synthesized via ring-opening polymerization (ROP) of ε-caprolactone. NDI-PCL showed a remarkable fluorescence change from blue to green and yellow because of the formation of charge transfer (CT) interaction between naphthalene diimide (NDI) and aromatic solvents. NDI-PCL was successfully applied as the high-sensitive sensor for discriminating binary solvent mixtures such as PX in TOL, MeOH in PX, and MeOH in TOL, and their limit of detection (LOD) were as low as 19 ppm, 16 ppm and 9 ppm. These excellent fluorescence properties ensured that NDI-PCL indicated great potential application in detecting aromatic solvents.

Nanoscale assembly of enantiomeric supramolecular gels driven by the nature of solvents.

Understanding the key parameters that control the self-assembly process is critical to predict self-assembly modes in multi-component systems, which will lead to the development of nanofibrous materials with tuneable properties. Enantiomeric amino acid-based low-molecular-weight gelators (LMWGs) were mixed in polar (polar protic) and aromatic apolar (aromatic) solvents and compared to their individual counterparts to probe the effect of solvent polarity on the self-assembly process. Scanning electron microscopy (SEM) reveals that xerogels of individual components display hollow needles in polar protic solvents, while chiral coils are observed in aromatic solvents. In contrast, the multi-component gel displays hollow needle morphologies in both solvents, indicating similar morphologies in polar protic solvents but an entirely different nanostructure for the individual gel networks in aromatic solvents. PXRD experiments performed on the dried gels showed that the nature of the solvents plays a vital role in the co-assembly process of multi-component gels. The self-assembly modes and the gel state structure of the gels are analysed by wide-angle X-ray diffraction (WAXS) and small-angle neutron diffraction (SANS), which reveals that the mixed gel undergoes different co-assembly modes depending on the nature of the solvent systems. This study shows that different co-assembly modes can be achieved for structurally similar components by varying the solvent polarity, demonstrating the importance of solvent choice in the self-assembly process of multi-component gels.

Solvent effects on the intramolecular charge transfer excited state of 3CzClIPN: a broadband transient absorption study.

The prediction of solvent properties using molecular probes often relies on correlating steady-state absorption and fluorescence measurements, as well as determining absorption maxima and/or Stokes shifts. In this study, we employ femtosecond broadband transient absorption (fs-bb-TA) spectroscopy to investigate the spectroscopic behaviour of the intramolecular charge transfer (ICT) excited state of 3CzClIPN (2,4,6-tri(9H-carbazol-9-yl)-5-chloroisophthalonitrile), a representative ICT organic molecule, in both aromatic and non-aromatic solvents. Unlike observations in non-aromatic media, fs-bb-TA spectra of 3CzClIPN in aromatic solvents exhibit enhanced spectral broadening that strongly correlates with the solvent's polarity. We hypothesise that this spectral broadening originates from a wider configurational energy landscape experienced by the positively charged carbazole Cz+ group, owing to the larger size and, consequently, reduced solvation effectiveness of aromatic solvent molecules.

Isothermal and non-isothermal transport properties of diluted fullerene binary and ternary aromatic solvent mixtures.

We present mass transport properties of C60 fullerene in five aromatic solvents, methylnaphthalene, toluene and three xylene isomers. Optical beam deflection and thermogravitational column techniques were used to determine molecular diffusion, thermodiffusion and Soret coefficients. All thermo-optical properties necessary to determine the abovementioned coefficients are also given at a mean working temperature of 298.15 K and an atmospheric pressure of 0.101 MPa. The magnitude of all transport properties is governed by the molecular weight ratio. In the particular case of the isomers, experiments revealed that movement under isothermal conditions (described by molecular diffusion) is dominated by density, while under non-isothermal conditions viscous forces affect the displacement (thermodiffusion depends on the dynamic viscosity). In the case of the Soret coefficients, as a combination of both, density is the dominant parameter and also the moment of inertia.

Selenium reduction pathways in the colloidal synthesis of CdSe nanoplatelets.

Several established procedures are now available to prepare zinc blende CdSe nanoplatelets. While these protocols allow for detailed control over both thickness and lateral dimensions, the chemistry behind their formation is yet to be unraveled. In this work, we discuss the influence of the solvent on the synthesis of nanoplatelets. We confirmed that the presence of double bonds, as is the case for 1-octadecene, plays a key role in the evolution of nanoplatelets, through the isomerization of the alkene, as confirmed by nuclear magnetic resonance spectroscopy and mass spectrometry. Consequently, 1-octadecene can be replaced as a solvent (or solvent mixture), however, only by one that also contains α protons to CC double bonds. We confirm this via synthesis of nanoplatelets in hexadecane spiked with a small amount of 1-octadecene, and in the aromatic solvent 1,2,3,4-tetrahydronaphthalene (tetralin). At the same time, the chemical reaction leading to the formation of nanoplatelets occurs to some extent in saturated solvents. A closer examination revealed that an alternative formation pathway is possible, through interaction of carboxylic acids, such as octanoic acid, with selenium. Next to shedding more light on the synthesis of CdSe nanoplatelets, fundamental understanding of the precursor chemistry paves the way to use optimized solvent admixtures as an additional handle to control the nanoplatelet synthesis, as well as to reduce potential self-polymerization hurdles observed with 1-octadecene.

Исследование строения -дикетонатов тетраарилсурьмы Ph4Sb[MeC(O)CHC(O)Ph], p-Tol4Sb[MeC(O)CEtC(O)Me] ∙ 1½ PhH, p-Tol4Sb[MeC(O)СHC(O)NHPh

Reaction of pentaphenylantimony and penta(para-tolyl)antimony with -diketones in benzene (100 °C, 1 h) forms tetraarylantimony -diketonates Ph4Sb[MeC(O)CHC(O)Ph] (1), p-Tol4Sb[MeC(O)CEtC(O)Me] ∙ 1½PhH (2), p-Tol4Sb[MeC(O)СHC(O)NHPh] (3), characterized by IR spectra and X-ray diffraction analysis. Crystals 1 [C34H29O2Sb, M 591.32; triclinic system, symmetry group P–1; cell parameters: a = 9.524(13) Å, b = 9.827(10) Å, c = 17.350(18) Å;  = 99.03(3), β = 101.50(6),  = 111.02(4), V = 1438(3) Å3, Z = 2; cal = 1.365 g/cm3], 2 [C44H48O2Sb, M 730.57; triclinic system, symmetry group P–1; cell parameters: a = 9.740(5) Å, b = 14.283(6) Å, c = 15.174(6) Å;  = 107.818(14), β = 90.292(18),  = 105.33(2), V = 1929,7(16) Å3, Z = 2; cal = 1.257 g/cm3], 3 [C34H30NO2Sb, M 606.34; monoclinic system, symmetry group P21/n; cell parameters: a = 9.396(17) Å, b = 10.23(2) Å, c = 29.45(6) Å; β = 95.91(6), V = 2817(10) Å3, Z = 4; cal = 1.430 g/cm3]. The obtained tetraarylantimony -diketonates are crystal-line compounds with a distinct melting point, resistant to moisture and atmospheric oxygen, and highly soluble in aromatic solvents and polyhalide solvents. Complex 2 is a solvate and contains 1½ benzene molecules. According to the X-ray diffraction data, the antimony atoms in complexes 1–3 have a distorted octahedral coordination, with the chelate ring and two aryl substituents locat-ed in the equatorial plane, while two aryl ligands occupy axial positions.

ANALYSIS OF DISSOLVING ABILITY OF LOWER ALCOHOLS AND ESTERS AQUEOUS AND HYDROCARBON SOLUTIONS TO ORGANIC MATTER OF BAZHENOV FORMATION ROCKS

This work is devoted to studying the characteristics of treatments with organic solvents on bazhenov formation rock samples, which contains a large amount of unconverted organic matter (kerogen, bitumen). This article contains the results of studying the dissolving abilities of individual low-molecular alcohols and esters, and solutions of these compounds in water and in a non-polar aromatic solvent (petroleum solvent). Among the individual solvents studied, esters of acetic acid showed the greatest dissolving ability; alcohols are less active. Petroleum solvent slightly dissolves the rock’s organic matter and needs the addition of more polar organic compounds. The dependences of dissolving ability of alcohols’ hydrocarbon solutions on alcohol concentration is extreme, with a maximum of 10 wt.%. Based on the obtained results, the mutual influence of solvents in the hydrocarbon fluid was additionally evaluated. It has been established that solutions of isopropanol and aromatic solvent show a synergistic effect to the dissolution of rock organic matter more than hydrocarbon solutions of esters. For the compositions that showed the greatest dissolving ability, a qualitative and semi-quantitative analysis was made for establishing changes in the composition of rock samples after extraction using X-Ray diffraction and Fourier-transform infrared spectroscopy. It is shown that mixtures of polar and non-polar solvents provide a more regular extraction of aliphatic and aromatic components of rock organic matter. Systems containing petroleum solvent, isopropanol and isopropyl acetate have been identified as the basis for the development of process fluids for increasing oil recovery in organic-rich reservoirs.

Solvent–base mismatch enables the deconstruction of epoxy polymers and bisphenol A recovery

The use of an alkaline base mismatched with an apolar aromatic solvent provides a new route to disassemble thermoset epoxy resins resulting in the recovery of the polymer building block bisphenol A.

Synthesis and characterization of a series of U(IV) trans-bis(phosphaylide)UX4 (X = Cl, Br, I) adducts

Addition of 2 equiv. of the phosphaylide reagents CH2PAr3 (Ar = Ph; 3,5-di-tert-butylphenyl (tBuAr)) to the tetravalent uranium halides, UX4(solvent)n (X = Cl, n = 0; X = Br, solvent = THF, n = 2; X = I, solvent = 1,4-dioxane, n = 2), generates the trans-bis(phosphaylide) adducts UX4(CH2PAr3)2 (Ar = Ph, X = Cl (1Ph-Cl), I (1Ph-I); Ar = tBuAr, X = Cl (2tBu-Cl), Br (2tBu-Br), I (2tBu-I)) in low to good yields. Complexes 1Ph-X exhibit poor solubility in aromatic solvents but are partially soluble in 1,2-difluorobenzene (o-DFB), while 2tBu-X possesses greatly improved solubility in these solvents. The solid-state molecular structures of 1Ph-X·C7H8 and 2tBu-X·n(o-DFB), reveal U-Cylide bonds that range from = 2.506(3)–2.58(1) Å, generally shorter than those found in other uranium-phosphaylide (2.60(1)–2.71(1) Å) and untethered, monodentate U-CNHC (2.62(1)–2.79(1) Å) complexes. Notably, a general contraction of the U-Cylide bond is observed in the UX4(CH2PAr3)2 as the halide series is descended. Attempts to oxidize 2tBu-Cl with Ag+ or Fc+ salts leads to complicated product mixtures from which a few crystals of {[(tBuAr)3PCH2]UCl3(μ-Cl)}2·C7H8 can be isolated, whereas addition of the reductant Cp*2Co to 2tBu-I, in the presence of an extra equiv. of CH2P(tBuAr)3, leads to the formation of the highly encumbered U(III) tris(phosphaylide) adduct UI3[CH2P(tBuAr)3]3 (3tBu-I). Preliminary experiments show these complexes are amenable to substitution reactions as treatment of 2tBu-Cl with 2 equiv. of LiCH2SiMe3 generates the thermally sensitive bis(alkyl) bis(phosphaylide) complex trans-UCl2[CH2P(tBuAr)3]2(CH2SiMe3)2 (4tBu-TMS), a mixed ylide-alkyl system featuring distinct U-Cylide and U-Calkyl σ-bonds. This chemistry demonstrates that untethered, neutral phosphaylide ligands, when coordinated to uranium, are compatible with redox transformations and metathesis reactions. The report of these UX4(CH2PAr3)2 complexes significantly expands the library of known uranium-phosphaylide compounds and contributes to the relatively small collection of uranium complexes featuring neutral C-donor ligands.

Colloid Chemistry of Fullerene Solutions: Aggregation and Coagulation

This review article is devoted to the colloidal properties of fullerene solutions. According to generally accepted understandings, all solvents in relations to fullerenes are divided into “good”, “poor”, and “reactive”. We have consistently considered the state of fullerenes in these systems. In “good”, predominantly non-polar aromatic solvents and CS2, non-equilibrium dissolution methods lead to the formation of colloidal aggregates, whereas the utilization of equilibrium methods results in the formation of molecular solutions. The latter, however, have some unusual properties; new results considered in this review confirm previously expressed ideas about colloidal properties of these solutions. In “poor” (polar) solvents, lyophobic colloidal systems appear. Both “bottom-up” and “top-down” methods of preparation are well documented in the literature. However, N-methylpyrrolidine-2-one, DMSO, and DMF dissolve fullerenes quite easily and with less energy consumption. These solvents can be considered a subset of “poor” solvents that have some features of being “reactive” at the expense of basic properties. New data confirm that hydrosols of fullerenes are typical hydrophobic colloids that obey the Schulze–Hardy rule and other regularities in the presence of electrolytes. Organosols in acetonitrile and methanol are much less stable with respect to the effects of electrolytes. This allows us to assume a non-DLVO stabilizing factor in the hydrosols. Accordingly, a new estimate of the Hamaker constant of fullerene–fullerene interaction is proposed. In DMSO and DMF, the coagulation of fullerene sols is hindered due to strong solvation with these basic solvents.