Unsaturated Chains Research Articles

Theoretical Study on Abstraction and Addition Reaction Kinetics for a Medium-Size Unsaturated Methyl Ester: Methyl-3-hexenoate + H/OH Radicals.

Combustion chemistry of methyl esters with long alkyl chains and different degrees of unsaturation has been of particular interest for biodiesel combustion. Methyl-3-hexenoate (mhx3d) with a medium-size unsaturated aliphatic chain is regarded as a valuable surrogate of biodiesel components. Here, the abstraction and addition reaction kinetics of mhx3d + H/OH radicals are comprehensively investigated. An accurate and efficient exchange-correlation density functional M06-2X/ma-TZVP is validated by the DLPNO-CCSD(T)/CBS(T-Q) benchmark calculations and is used for the multistructural search, geometry optimization, potential energy profiles, and direct dynamic calculations. The multistructural torsional (MS-T) anharmonicity, variational effects, and tunneling effects including one-dimensional Winger tunneling, multidimensional zero-curvature tunneling (ZCT), and small-curvature tunneling (SCT) are also evaluated in rate coefficient calculations. The existence of reactant complexes of the abstraction and addition reactions is neglected for mhx3d + H due to weak van der Waals interaction but is considered for mhx3d + OH. Therefore, a pre-equilibrium model is employed to obtain the rate coefficients for mhx3d + OH. The calculation results show that the MS-T factor ranges from 0.29 to 11.41, the tunneling transmission coefficient calculated by SCT is in the range of 1.0-4.0, and the recrossing transmission coefficient is between 0.65 and 1.0. Moreover, the two OH-addition reactions exhibit negative temperature coefficient behavior. The branching ratios show that the H/OH-addition reactions are dominant at lower temperature, especially for mhx3d + H. Rate coefficients of the title reactions are fitted in terms of a modified three-parameter Arrhenius expression.

Synthesis of Novel 3’,3’‐cyclic Dinucleotide Analogues Targeting STING Protein

AbstractThe Stimulator of Interferon Genes (STING) plays an important role in innate immunity by inducing type I interferons in response to sensing viral or bacterial cytosolic DNA. Cyclic dinucleotides (CDNs) are known to activate STING. Here, we describe the synthesis and biological evaluation of two new 3’,3’‐CDN, in which the internucleotide linkages were replaced, respectively, by a 1,2,3‐triazole moiety (as more stable isosteres of phosphate linkers) and an unsaturated carbon chain (as flexibility can led to crucial binding affinity and specificity). Thus, CuAAC and macrocyclization by RCM are the two key steps.

Orientation of Cholesterol in Polyunsaturated Lipid Bilayers.

The local normal to the fluid liquid crystalline phase of the lipid membrane is an axis of motional symmetry for the molecules that make up the bilayer. The presence of cholesterol in the membrane increases not only the lipid hydrocarbon chain order but also the strength of the membrane's orienting potential. Cholesterol undergoes rapid reorientation about a diffusion axis that is roughly aligned with the long molecular axis, but there is also a slower reorientation of the diffusion axis, or "wobble", relative to the local bilayer normal. The extent of this second, slower motion depends on the degree of order of the lipids that make up the bilayer. We use 2H nuclear magnetic resonance of deuterium-labeled cholesterol to investigate quantitatively the effect of lipid chain unsaturation on cholesterol orientation in a series of phospholipid bilayers. We find that the hydrocarbon chains in membranes composed of polyunsaturated lipids are much more highly disordered than those in membranes composed of saturated lipids but that cholesterol remains aligned roughly along the bilayer normal.

Structure Analysis of Unsaturated Polymyxin E Components Based on High-Performance Liquid Chromatography - Quadrupole/ Time of Flight Tandem Mass Spectrometry and Photochemical Reaction

Background: Polymyxin E (PME), which is a complex of cationic cyclic lipodecapeptides, is used to treat multidrug-resistant gram-negative bacterial infections. Besides the main components PME1 and PME2, polymyxin containing unsaturated fatty acyl (FA) group with lower contents is hardly to determine the structure without chromatographic preparations and NMR. Introduction: The peptide sequences of PME components has been carried out based on high performance liquid chromatography-quadrupole / time-of-flight mass spectrometry (HPLC-Q/TOF-MS). However, the components with double bond on the FA, such as 2’, 3’-dehydro PME1, were difficult to be determined or easily misjudged by MS/MS. The transformation of such unsaturated components to be epoxidized components or di-hydroxylated components can promote the acquisition of more fragment ions in the MS/MS, so as to assist in judging the position of double bonds on FA. Methods: In this paper, the PME mixtures were dissolved in an equal proportion of 20% ACN aqueous solution and 2-acetylpyridine. The above PME solution was transferred to a quartz cuvette and irradiated with the ultraviolet lamp at 254 nm for 8h. The dehydro PME components were converted to be epoxy PMEs and dihydroxy PMEs. A fragmentation pathway of epoxidized components or di-hydroxylated components based on Q/TOF-MS/MS was proposed for the first time. Results: According to the characteristic ions of epoxidized components and di-hydroxylated components, 2’, 3’-epoxy PME1/E2 and 2’, 3’-dihydroxy PME1/E2 were confirmed. It can be inferred that the double bond is located at the 2’, 3’-position of FA. Conclusion: The structure of unsaturated PME component with double bond on the FA is elucidated by HPLC-Q/TOF-MS combined with photochemical reaction. This strategy is applicable to other lipopeptides containing unsaturated FA chain.

Unsaturation pattern of phosphatidylglycerols modulating the interaction of lysicamine with cells membrane models at the air-water interface

Lysicamine, an alkaloid with tumorigenic activity, was incorporated in cell membrane models made of lipid Langmuir monolayers. Dipalmitoylphosphocholine (DPPC), dioleoylphosphocholine (DOPC), and palmitoyloleoylcholine (POPC) represented non-tumorigenic cell membranes, and dipalmitoylphosphoserine (DPPS), dioleoylphosphoserine (DOPS), and palmitoyloleoylserine (POPS), tumorigenic ones. The monolayers were characterized by tensiometry, infrared spectroscopy, and Brewster Angle Microscopy (BAM). No significant shifts of the isotherms were observed for the saturated lipids (DPPC and DPPS), while for the others (DOPC, POPS, DOPS, and POPS), more significant changes were observed not only in the compression isotherms but also in the surface pressure-time curve for pre-compressed monolayers. The molecular organization, as well as the morphology of the drug-lipid monolayers, could be inferred with infrared spectroscopy and BAM. While the first revealed that the alkyl chain ordering changed upon lysicamine incorporation, the second showed how the drug could distinctly change the state of aggregation of molecular domains at the air-water interface. In conclusion, lysicamine could interact distinctly with each lipid at the air-water interface, showing the dependence not only on the lipid polar groups but also on the level of unsaturation of the alkyl chains.

Quantitative lipidomics reveals lipid perturbation in the liver of fatty liver hemorrhagic syndrome in laying hens

Fatty liver hemorrhagic syndrome (FLHS) is a metabolic disease that causes decreased egg production and even death in laying hens, which brings huge economic losses to the poultry industry. However, the pathogenesis of FLHS is unclear. The purpose of the present study was to identify the changes in lipid profile and the lipid species related to FLHS. In the present study, the FLHS disease model in Chinese commercial Jing Fen laying hens was induced by a high-energy low-protein diet. A lipidomics approach based on ultra-performance liquid chromatography-mass spectrometry coupled with multivariate statistical analysis was performed for the qualitative and quantitative analyses of the liver lipids. The results showed that a total of 29 lipid subclasses, including 1,302 lipid species, were detected and identified. Among them, the proportions of phosphatidylserine (Control/FLHS, 33.1% vs. 29.1%), phosphatidylethanolamine (22.7% vs. 15.5%), phosphatidylcholine (15.7% vs. 11.7%) and phosphatidylinositol (7% vs. 6%) were reduced, while triacylglycerol (7.1% vs. 18.3%) and diglyceride (3.9% vs. 11.7%) were increased. Between the Control and FLHS groups, distinct changes in lipid profile were observed in the score plots of principal component analysis and orthogonal partial least squares discriminant analysis. Twelve differential lipid species mainly involved in glycerophospholipid metabolism and linoleic acid metabolism were identified and considered to be related to the pathogenesis of FLHS. Fatty acid chain length and unsaturation were reduced, while the mRNA levels of elongation of very long chain fatty acids-2 (ELOVL2) were increased in the liver of laying hens with FLHS. Collectively, this study characterized the liver lipid profile and explored the changes in lipid species related to FLHS, which provided insights into the pathogenesis of FLHS from the view of lipid metabolism.

Characterization of the Biosynthetic Gene Cluster and Shunt Products Yields Insights into the Biosynthesis of Balmoralmycin.

Angucyclines are a family of structurally diverse, aromatic polyketides with some members that exhibit potent bioactivity. Angucyclines have also attracted considerable attention due to the intriguing biosynthetic origins that underlie their structural complexity and diversity. Balmoralmycin (compound 1) represents a unique group of angucyclines that contain an angular benz[α]anthracene tetracyclic system, a characteristic C-glycosidic bond-linked deoxy-sugar (d-olivose), and an unsaturated fatty acid chain. In this study, we identified a Streptomyces strain that produces balmoralmycin and seven biosynthetically related coproducts (compounds 2-8). Four of the coproducts (compounds 5-8) are novel compounds that feature a highly oxygenated or fragmented lactone ring, and three of them (compounds 3-5) exhibited cytotoxicity against the human pancreatic cancer cell line MIA PaCa-2 with IC50 values ranging from 0.9 to 1.2 μg/mL. Genome sequencing and CRISPR/dCas9-assisted gene knockdown led to the identification of the ~43 kb balmoralmycin biosynthetic gene cluster (bal BGC). The bal BGC encodes a type II polyketide synthase (PKS) system for assembling the angucycline aglycone, six enzymes for generating the deoxysugar d-olivose, and a hybrid type II/III PKS system for synthesizing the 2,4-decadienoic acid chain. Based on the genetic and chemical information, we propose a mechanism for the biosynthesis of balmoralmycin and the shunt products. The chemical and genetic studies yielded insights into the biosynthetic origin of the structural diversity of angucyclines. IMPORTANCE Angucyclines are structurally diverse aromatic polyketides that have attracted considerable attention due to their potent bioactivity and intriguing biosynthetic origin. Balmoralmycin is a representative of a small family of angucyclines with unique structural features and an unknown biosynthetic origin. We report a newly isolated Streptomyces strain that produces balmoralmycin in a high fermentation titer as well as several structurally related shunt products. Based on the chemical and genetic information, a biosynthetic pathway that involves a type II polyketide synthase (PKS) system, cyclases/aromatases, oxidoreductases, and other ancillary enzymes was established. The elucidation of the balmoralmycin pathway enriches our understanding of how structural diversity is generated in angucyclines and opens the door for the production of balmoralmycin derivatives via pathway engineering.

Conformations of Three Types of Ultra-Long-Chain Fatty Acids in Multicomponent Lipid Bilayers.

Ultra-long-chain fatty acids (ULCFAs) are biosynthesized in certain types of tissues, but their biological roles remain unknown. Here, we report how the conformation of ULCFAs depends on the length and unsaturated-bond ratio of the ultra-long chains and the composition of the host bilayer membrane using molecular dynamics simulations. The ultra-long chain of ULCFAs flips between the two leaflets and fluctuates among three conformations: elongated, L-shaped, and turned. Furthermore, we found that the saturated ultra-long chain exhibited an elongated conformation more frequently than the unsaturated chain. In addition, the truncation of the ultra-long chain at C26 had little effect on the remaining ULCFAs. ULCFAs respond to lipid-density differences in the two leaflets, and the ratio of the elongated and turned conformations changed to reduce this difference. However, in cholesterol-containing membranes, ULCFAs exhibit no density difference after the flip-flop of cholesterol removes the difference.

Short-clustered maltodextrin provides cryoprotection by maintaining cell membrane homeostasis of yeast during frozen storage

Cryoprotective polysaccharides have been extensively explored. We found that short-clustered maltodextrin (SCMD) effectively increased yeast viability. But the specific mechanism of SCMD affecting yeast is still not clear. Here, we detailedly analyze the effects of SCMD addition on cell membrane homeostasis. Firstly, the high-branched structure of SCMD was observed, and the microstructure of SCMD-protecting yeast was more integral. Analysis of membrane physicochemical property and glycerophospholipid metabolism demonstrated the fluidity of cell membrane of SCMD-protecting yeast was enhanced, as the relative abundances of glycerophospholipids with unsaturated acyl chains increased in comparison to Control yeast. Further, molecular dynamics simulations found that simplified SCMD could form more H-bonds with water molecules around lipid bilayers at 250 K to promote the mobility of lipid bilayers. Therefore, the hypothesis of “SCMD existence promotes the membrane fluidity under ice-crystal stress during frozen storage and helps maintain cell membrane homeostasis after thawing, increasing the thawed yeast viability” is proposed.

Bio-based coating resins derived from cardanol using carbocationic polymerization and their evaluation as one-component alkyd-type coatings

A novel biobased monomer, cardanol ethyl vinyl ether (CEVE) and its autooxidatively curable linear homopolymer and copolymers were synthesized using carbocationic polymerization. Cardanol, a component of cashew nut-shell liquid has a unique phenolic structure with an unsaturated fatty chain. The polymers were cured oxidatively at both ambient and elevated temperatures (120 and 150 °C) resulting in crosslinked networks with better physical and thermomechanical properties than two commercial reference alkyds. Variations in the glass transition temperature (Tg) (5.6 to 26 °C), crosslink density (3.92 to 16.6 mol/cm3), tensile properties (12.2 to 26.6 MPa), and hardness (15 to 40 Sec.) were achieved by changing the copolymer composition from poly(CEVE) to poly(CEVE-co-CHVE)-50/50. These results clearly show the potential of these cardanol-based polymers for use as surface coatings.

Dynamic modulations of sphingolipids and glycerophospholipids in COVID-19.

BackgroundA heterogeneous clinical phenotype is a characteristic of coronavirus disease 2019 (COVID‐19). Therefore, investigating biomarkers associated with disease severity is important for understanding the mechanisms responsible for this heterogeneity and for developing novel agents to prevent critical conditions. This study aimed to elucidate the modulations of sphingolipids and glycerophospholipids, which have been shown to possess potent biological properties.MethodsWe measured the serum sphingolipid and glycerophospholipid levels in a total of 887 samples from 215 COVID‐19 subjects, plus 115 control subjects without infectious diseases and 109 subjects with infectious diseases other than COVID‐19.ResultsWe observed the dynamic modulations of sphingolipids and glycerophospholipids in the serum of COVID‐19 subjects, depending on the time course and severity. The elevation of C16:0 ceramide and lysophosphatidylinositol and decreases in C18:1 ceramide, dihydrosphingosine, lysophosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol were specific to COVID‐19. Regarding the association with maximum severity, phosphatidylinositol and phosphatidylcholine species with long unsaturated acyl chains were negatively associated, while lysophosphatidylethanolamine and phosphatidylethanolamine were positively associated with maximum severity during the early phase. Lysophosphatidylcholine and phosphatidylcholine had strong negative correlations with CRP, while phosphatidylethanolamine had strong positive ones. C16:0 ceramide, lysophosphatidylcholine, phosphatidylcholine and phosphatidylethanolamine species with long unsaturated acyl chains had negative correlations with D‐dimer, while phosphatidylethanolamine species with short acyl chains and phosphatidylinositol had positive ones. Several species of phosphatidylcholine, phosphatidylethanolamine and sphingomyelin might serve as better biomarkers for predicting severe COVID‐19 during the early phase than CRP and D‐dimer. Compared with the lipid modulations seen in mice treated with lipopolysaccharide, tissue factor, or histone, the lipid modulations observed in severe COVID‐19 were most akin to those in mice administered lipopolysaccharide.ConclusionA better understanding of the disturbances in sphingolipids and glycerophospholipids observed in this study will prompt further investigation to develop laboratory testing for predicting maximum severity and/or novel agents to suppress the aggravation of COVID‐19.

Stimulating the sir2-spargel axis rescues exercise capacity and mitochondrial respiration in a Drosophila model of Barth syndrome.

ABSTRACTCardiolipin (CL) is a phospholipid required for proper mitochondrial function. Tafazzin remodels CL to create highly unsaturated fatty acid chains. However, when TAFAZZIN is mutated, CL remodeling is impeded, leading to mitochondrial dysfunction and the disease Barth syndrome. Patients with Barth syndrome often have severe exercise intolerance, which negatively impacts their overall quality of life. Boosting NAD+ levels can improve symptoms of other mitochondrial diseases, but its effect in the context of Barth syndrome has not been examined. We demonstrate, for the first time, that nicotinamide riboside can rescue exercise tolerance and mitochondrial respiration in a Drosophila Tafazzin mutant and that the beneficial effects are dependent on sir2 and spargel. Overexpressing spargel increased the total abundance of CL in mutants. In addition, muscles and neurons were identified as key targets for future therapies because sir2 or spargel overexpression in either of these tissues is sufficient to restore the exercise capacity of Drosophila Tafazzin mutants.

Cholesterol Stiffening of Lipid Membranes.

Biomembrane order, dynamics, and other essential physicochemical parameters are controlled by cholesterol, a major component of mammalian cell membranes. Although cholesterol is well known to exhibit a condensing effect on fluid lipid membranes, the extent of stiffening that occurs with different degrees of lipid acyl chain unsaturation remains an enigma. In this review, we show that cholesterol locally increases the bending rigidity of both unsaturated and saturated lipid membranes, suggesting there may be a length-scale dependence of the bending modulus. We review our published data that address the origin of the mechanical effects of cholesterol on unsaturated and polyunsaturated lipid membranes and their role in biomembrane functions. Through a combination of solid-state deuterium NMR spectroscopy and neutron spin-echo spectroscopy, we show that changes in molecular packing cause the universal effects of cholesterol on the membrane bending rigidity. Our findings have broad implications for the role of cholesterol in lipid–protein interactions as well as raft-like mixtures, drug delivery applications, and the effects of antimicrobial peptides on lipid membranes.Graphical

Structural changes in fasted state dietary mixed micelles upon solubilization of beta-carotene

It was aimed to investigate the structural changes taking place in duodenal mixed micelles (MM) at fasted state with the incorporation of fatty acids (FA) and the morphological transformations in these MMs upon solubilization of β-carotene (BCR) through coarse-grained (CG) molecular dynamics (MD) simulations. All simulations were performed with GROMACS 2019 simulation package using the Martini force field. Lauric acid (LA), stearic acid (SA) and linoleic acid (LNA) were used to explore the effects of FA chain length and unsaturation. Micelle swelling was observed with the incorporation of all FAs. The increase in size was in line with increasing FA chain length and unsaturation. MMs incorporating LA and SA were ellipsoidal in shape, while polyunsaturated LNA resulted in a worm-like MM. Upon solubilization of BCRs, swelling was observed only in the MMs with long-chain SA and LNA. No micelle growth was observed in the plain and LA MMs despite their smaller sizes. This was attributed to their low-density hydrophobic cores, which allowed a condensation effect induced by the interactions between BCRs and POPC tails. It is inferred that when the micelle is large enough to solubilize BCRs, whether or not swelling will take place depends on the core density. The increase in micelle size was very small in the MM incorporating LNA compared to that in the MM with SA, which was accompanied by an elliptical-to-cylindrical shape transformation. This was due to the fluid nature of the worm-like LNA micelle, which readily allowed the solubilization of 3 BCRs within its core. By resolving the internal structures of BCR incorporated MMs, this study gives valuable insight into the effects of FA chain length and unsaturation on the solubilization behavior of dietary MMs. The results are expected to give direction to the development of rational design strategies for effective BCR delivery systems.

A DFT Study on the Excited Electronic States of Cyanopolyynes: Benchmarks and Applications.

Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HC2m+1N (m = 0–13) and dinitriles NC2n+2N (n = 0–14). The results of time-dependent density functional theory (TD-DFT) calculations are compared with the available gas-phase and noble gas matrix experimental data. We assessed the performance of fifteen functionals and five basis sets for reproducing (i) vibrationless electronic excitation energies and (ii) vibrational frequencies in the singlet excited states. We found that the basis sets of at least triple-ζ quality were necessary to describe the long molecules with alternate single and triple bonds. Vibrational frequency scaling factors are similar for the ground and excited states. The benchmarked spectroscopic parameters were shown to be acceptably reproduced with adequately chosen functionals, in particular ωB97X, CAM-B3LYP, B3LYP, B971, and B972. Select functionals were applied to study the electronic excitation of molecules up to HC27N and C30N2. It is demonstrated that optical excitation leads to a shift from the polyyne- to a cumulene-like electronic structure.

Fabrication and characterizations of cyclic amylopectin-based delivery system incorporated with β-carotene

The aim of this work was to investigate the encapsulation potential of cyclic amylopectin (CA) as a novel delivery carrier for fortifying the solubility and environmental stability of β-carotene (βC). After measuring solubility, recovery, encapsulation rate and loading rate, the optimum ratio of CA to βC in the composite (CA-βC) was 5:1. The solubility of βC in the optimal composite reached a maximum value of 179.1 μg/mL and was significantly higher than that of raw βC. Structural characterizations showed that the βC crystals were successfully entrapped into the hydrophobic cavity of CA, resulting in a composite with an amorphous state. A higher stability of βC to light or chemical oxidation was observed. Additionally, in-silico simulations showed that the partially unsaturated fatty acid chain of the βC molecule was bound into the hydrophobic core of CA through hydrophobic interaction. Results indicate that CA is a suitable compound to encapsulate and improve the functionality of lipophilic phytochemicals. • CA-based delivery system significantly enhanced the water solubility of βC. • Composite showed the higher stability of βC against light and chemical oxidation. • Crystal βC was successfully entrapped into the hydrophobic cavity of CA. • CA is an attractive platform to improve the functionalities of phytochemicals.

Rotational Spectra of Unsaturated Carbon Chains Produced by Pyrolysis: The Case of Propadienone, Cyanovinylacetylene, and Allenylacetylene.

Several interstellar molecules are highly reactive unsaturated carbon chains, which are unstable under terrestrial conditions. Laboratory studies in support of their detection in space thus face the issue of how to produce these species and how to correctly model their rotational energy levels. In this work, we introduce a general approach for producing and investigating unsaturated carbon chains by means of selected test cases. We report a comprehensive theoretical/experimental spectroscopic characterization of three species, namely, propadienone, cyanovinylacetylene, and allenylacetylene, all of them being produced by means of flash vacuum pyrolysis of a suitable precursor. For each species, quantum-chemical calculations have been carried out with the aim of obtaining accurate predictions of the missing spectroscopic information required to guide spectral analysis and assignment. Rotational spectra of the title molecules have been investigated up to 400 GHz by using a frequency-modulation millimeter-/submillimeter-wave spectrometer, thus significantly extending spectral predictions over a wide range of frequency and quantum numbers. A comparison between our results and those available in the literature points out the clear need of the reported laboratory measurements at higher frequencies for setting up accurate line catalogs for astronomical searches.

Rapid calculation of the number of π-bonds, σ-bonds, single and double bonds in aliphatic unsaturated open chain and cyclic olefinic hydrocarbons

Rapid calculation of the number of π-bonds, σ-bonds, single and double bonds in aliphatic unsaturated open chain and cyclic olefinic hydrocarbons

Non-Covalent Interactions in Triglycerides: Vaporisation Thermodynamics for Quantification of Dispersion Forces

Qualitatively, the non-covalent interactions are well-known and help to explain many phenomena in chemistry and biochemistry. Quantitatively, determination of strength this force is a challenging task. The vaporization enthalpy is a reliable measure not only for the intermolecular interactions in the liquid phase, but also as the measure of intermolecular non-covalent interactions in the gas phase for the specific group of compounds, e.g., for the triglycerides. The vaporisation thermodynamics of four triglycerides were studied by using transpiration method, quartz crystal microbalance, and thermogravimetric analysis. Vapour pressure–temperature dependences were used to derive the enthalpies of vaporisation of these very low volatile liquids. Vaporisation enthalpies of the triglycerides available in the literature were collected and uniformly adjusted to the reference temperature 298.15 K and validated using structure–property relationships (chain-length dependence, correlation with retention indices, and correlation with normal boiling points). The consistent sets of evaluated vaporisation enthalpies for the linear and branched triglycerides were used to develop the “centerpiece” based group-additivity method for predicting enthalpies of vaporisation of triglycerides. It has turned out that the family of triglycerides do not obey the group-additivity rules. The reason for that is that the evaporated in the gas phase triglycerides exhibit intensive non-covalent attractive dispersion interactions strongly dependent on the alkyl-chain length. For the first time the intensity of the dispersion interactions was quantified for the family of aliphatic linear triglycerides with the chain length from 3 to 18 carbon atoms. The influence of the branching and unsaturation of the alkyl chains to the strength of the non-covalent interactions was also discussed.

Thio-imino-tetrahydroacridine Iron Complexes for Ethylene Polymerization

A series of thio-imino-tetrahydroacridine iron complexes, (TITha)FeCl2, were synthesized and applied to ethylene polymerization. This class of NNS type iron complexes were designed by integrating a fused ligand backbone into our previously reported thio-imino-quinoline iron complexes (TIQ)FeCl2, with a major purpose to improve the thermal stability. Among the (TITha)FeCl2 series, complex 3c with ortho-Et substituents on the N-aryl ring exhibits high activity and thermal stability [up to 10.1 × 106 g of PE (mol of Fe)−1 h–1 at 50 °C and 2.3 × 106 g of PE (mol of Fe)−1 h–1 at 100 °C], producing highly linear low molecular weight polyethylene wax with narrow molecular weight distributions and unsaturated chain end. The comparison of catalytic behavior between (TITha)FeCl2 and (TIQ)FeCl2 indicates the modification of the tridentate ligand by introducing a more rigid backbone not only enhances the catalytic performance at high temperature but also exerts a significant impact on controlling the structures of the polymers.