Berberine Inhibits Dengue Virus through Dual Mechanisms

Mosquito transmitted viruses, particularly those of the genus Flavivirus, are a significant healthcare burden worldwide, especially in tropical and sub-tropical areas. However, effective medicines for these viral infections remains lacking. Berberine (BBR) is an alkaloid found in some plants used in traditional medicines in Southeast Asia and elsewhere, and BBR has been shown to possess anti-viral activities. During a screen for potential application to mosquito transmitted viruses, BBR was shown to have virucidal activity against dengue virus (DENV; IC₅₀ 42.87 µM) as well as against Zika virus (IC₅₀ 11.42 µM) and chikungunya virus (IC₅₀ 14.21 µM). BBR was shown to have cellular effects that lead to an increase in cellular DENV E protein without a concomitant effect on DENV nonstructural proteins, suggesting an effect on viral particle formation or egress. While BBR was shown to have an effect of ERK1/2 activation this did not result in defects in viral egress mechanisms. The primary effect of BBR on viral production was likely to be through BBR acting through AMPK activation and disruption of lipid metabolism. Combined these results suggest that BBR has a dual effect on DENV infection, and BBR may have the potential for development as an anti-DENV antiviral.     

The first chelating olefin: Solid-state structure of bis-(η-4-phenyl-η-1-butene)silver (I) tetrafluoroborate

A complex of 4-phenyl-1-butene with silver ion has been prepared by mixing silver (I) tetrafluoroborate with the neat ligand at room temperature. Purification by crystallization produces a stable complex characterized by solid-state structure. The bis-(η¹-4-phenyl-η²-1-butene)silver (I) tetrafluoroborate complex contains a pair of olefin ligands that chelate a single silver atom via both olefin and aromatic Ag-C bonds. This is the first chelated organometallic silver complex reported in the literature assembled with only Ag-C bonds.     

Combining metal-microbe and microbe-microbe dual direct electron transfer on Fe(0)-cathode of bio-electrochemical system to enhance anaerobic digestion of cellulose wastewater

Considering that cathode of microbial electrochemical system (MES) is a good electrons source for methane production via direct/indirect electron transfer to electroactive microorganisms, and that Fe(0) is also a confirmed electron donor for some electroactive microorganisms through metal-microbe direct electron transfer (DET), Fe(0)-cathode was equipped into an MES digester to enhance cathodic methane production. The results of this study indicated that the potential DET participator, Clostridium possibly obtained electrons directly from Fe(0)-cathode via metal-microbe electrons transfer, then transferred electrons directly to the definite DET participators, Methanosarcina/Methanothrix via microbe-microbe electrons transfer for CH₄ production. In addition, Methanobacterium is another specially enriched methanogen on Fe(0)-cathode, which might obtain electrons directly from Fe(0)-cathode to produce CH₄ via metal/electrode-microbe DET. The increment of conductivity of cathodic sludge in Fe(0)-cathode MES digester (R1) further confirmed the enrichment of electroactive microorganisms participating in DET process. As a consequence, a higher CH₄ production (1205–1508 mL/d) and chemical oxygen demand (COD) removal (79.0%-93.8%) were achieved in R1 compared with graphite-cathode MES digester (R2, 720–1090 mL/d and 63.6%-85.6%) and the conventional anaerobic digester (R3, 384–428 mL/d and 35.2%-41.0%). In addition, energy efficiency calculated indicated that the output energy of CH₄ production was 8.16 folds of electricity input in Fe(0)-cathode MES digester.     

Ru single atoms induce surface-mediated discharge in Na-O2 batteries

Sodium（Na）O₂ batteries have high energy density and low cost. However, high polarization, complex discharge products, and low Coulombic efficiency（CE） lead to poor cyclability. Here, we proposed an atomically dispersed Ru catalyst on nitrogen-doped graphene for Na-O₂ batteries. The catalysts enable the discharge to proceed via a surface-mediated route, which leads to uniform deposition of Na_2-xO₂ and low polarization during recharge. The first-principl...     

Helicity-driven chiral self-sorting supramolecular polymerization with Ag+: right- and left-helical aggregates

The study of chiral self-sorting is extremely important for understanding biological systems and for developing applications for the biomedical field. In this study, we attempted unprecedented chiral self-sorting supramolecular polymerization accompanying helical inversion with Ag⁺ in one enantiomeric component. Bola-type terpyridine-based ligands (R-L¹ and S-L¹) comprising R- or S-alanine analogs were synthesized. First, R-L¹ dissolved in DMSO/H₂O (1 : 1, v/v) forms right-handed helical fibers (aggregate I) via supramolecular polymerization. However, after the addition of AgNO₃ (0.2–1.1 equiv.) to the R-L¹ ligand, in particular, it was found that aggregate II with left-handed helicity is generated from the [R-L¹(AgNO₃)₂] complex through the [R-L¹Ag]⁺ complex via the dissociation of aggregate I by a multistep with an off pathway, thus demonstrating interesting self-sorting properties driven by helicity and shape discrimination. In addition, the [R-L¹(AgNO₃)₂] complex, which acted as a building block to generate aggregate III with a spherical structure, existed as a metastable product during the formation of aggregate II in the presence of 1.2–1.5 equiv. of AgNO₃. Furthermore, the AFM and CD results of two samples prepared using aggregates I and III with different volume ratios were similar to those obtained upon the addition of AgNO₃ to free R-L¹. These findings suggest that homochiral self-sorting in a mixture system occurred by the generation of aggregate II composed of the [R-L¹Ag]⁺ complex via the rearrangement of both, aggregates I and III. This is a unique example of helicity- and shape-driven chiral self-sorting supramolecular polymerization induced by Ag⁺ starting from one enantiomeric component. This research will improve understanding of homochirality in complex biological models and contribute to the development of new chiral materials and catalysts for asymmetric synthesis.

Chiral self-sorting supramolecular polymerization of bola-type terpyridine-based ligands (R-L¹ and S-L¹) comprising R- or S-alanine analogs occurred upon addition of Ag⁺ in one enantiomeric component.     

Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C₃H₅NS₂)] was synthesized and characterized by chemical and spectroscopic measurements, DFT studies and biological assays. Infrared (IR) and ¹H, ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on DFT confirmed nitrogen coordination to gold(I) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Thermal decomposition starts at temperatures near 160 °C, leading to the formation of Au⁰ as the final residue at 1000 °C. The gold(I) complex with 2-mercaptothiazoline (Au-MTZ) is soluble in dimethyl sulfoxide (DMSO), and is insoluble in water, methanol, ethanol, acetonitrile and hexane. The antibacterial activities of the Au-MTZ complex were evaluated by an antibiogram assay using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of the cytotoxic effect of the Au-MTZ complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a potent cytotoxic activity, inducing 85% of cell death at a concentration of 2.0 μmol L⁻¹.     

Visible light-mediated radical fluoromethylation via halogen atom transfer activation of fluoroiodomethane

Incorporation of the fluoromethyl group can profoundly influence the physicochemical properties of organic molecules, offering a promising strategy for the discovery of novel pharmaceutical agents. Direct fluoromethylation of unfunctionalized C(sp²) centres can be achieved using fluoromethyl radicals, but current methods for their generation usually rely on the activation of non-commercial or expensive radical precursors via inefficient single electron transfer pathways, which limits their synthetic application. Here we report the development of a fluoromethylation strategy based on the generation of fluoromethyl radicals from commercially available fluoroiodomethane via halogen atom transfer. This mode of activation is orchestrated by visible light and tris(trimethylsilyl)silane, which serves as both a hydrogen- and halogen atom transfer reagent to facilitate the formation of C(sp³)–CH₂F bonds via a radical chain process. The utility of this metal- and photocatalyst-free transformation is demonstrated through the multicomponent synthesis of complex α-fluoromethyl amines and amino acid derivatives via radical addition to in situ-formed iminium ions, and the construction of β-fluoromethyl esters and amides from electron-deficient alkene acceptors. These complex fluoromethylated products, many of which are inaccessible via previously reported methods, may serve as useful building blocks or fragments in synthetic and medicinal chemistry both in academia and industry.

Generation of fluoromethyl radicals via visible light-mediated halogen atom transfer activation of fluoroiodomethane facilitates both the multicomponent synthesis of α-fluoromethyl amines and the hydrofluoromethylation of electron-deficient alkenes.     

On-off-on fluorescence detection for biomolecules by a fluorescent cage through host-guest complexation in water

Detection of nucleoside derivatives has paramount importance because they are the essential biomolecular units for all life. Herein, we report a host-guest approach by using a fluorescent tetraphenylethenebased octacationic cage as host and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt(HPTS) as guest and fluorescent indicator to form non-fluorescent 1:1:1 host-(endo-exo)guest complex in water. This new host-(endo-exo)guest complex can be successfully used for detecting nucleosides(e.g., ...     

Lewis acid catalyzed heavy atom tunneling – the case of 1H-bicyclo[3.1.0]-hexa-3,5-dien-2-one

For many thermal reactions, the effects of catalysis or the influence of solvents on reaction rates can be rationalized by simple transition state models. This is not the case for reactions controlled by quantum tunneling, which do not proceed via transition states, and therefore lack the simple concept of transition state stabilization. 1H-Bicyclo[3.1.0]-hexa-3,5-dien-2-one is a highly strained cyclopropene that rearranges to 4-oxocyclohexa-2,5-dienylidene via heavy-atom tunneling. H₂O, CF₃I, or BF₃ form Lewis acid–base complexes with both reactant and product, and the influence of these intermolecular complexes on the tunneling rates for this rearrangement was studied. The tunneling rate increases by a factor of 11 for the H₂O complex, by 23 for the CF₃I complex, and is too fast to be measured for the BF₃ complex. These observations agree with quantum chemical calculations predicting a decrease in both barrier height and barrier width upon complexation with Lewis acids, resulting in the observed Lewis acid catalysis of the tunneling rearrangement.

The ring-opening of a highly strained cyclopropene to a carbene proceeds via heavy-atom tunneling. This rearrangement is accelerated in the presence of H₂O, ICF₃ or BF₃, resulting in a novel Lewis-acid catalyzed tunneling reaction.     

Identification of potential inhibitors against nuclear Dam1 complex subunit Ask1 of Candida albicans using virtual screening and MD simulations

Identification of hit compounds against specific target form the starting point for a drug discovery program. A consistent decline of new chemical entities (NCEs) in recent years prompted a challenge to explore newer approaches to discover potential hit compounds that in turn can be converted into leads, and ultimately drug with desired therapeutic efficacy. The vast amount of omics and activity data available in public databases offers an opportunity to identify novel targets and their potential inhibitors. State of the art in silico methods viz., clustering of compounds, virtual screening, molecular docking, MD simulations and MMPBSA calculations were employed in a pipeline to identify potential ‘hits’ against those targets as well whose structures, as of now, could only predict through threading approaches. In the present work, we have started from scratch, amino acid sequence of target and compounds retrieved from PubChem compound database, modeled it in such a way that led to the identification of possible inhibitors of Dam1 complex subunit Ask1 of Candida albicans. We also propose a ligand based binding site determination approach. We have identified potential inhibitors of Ask1 subunit of a Dam1 complex of C. albicans, which is required to prevent precocious spindle elongation in pre-mitotic phases. The proposed scheme may aid to find virtually potential inhibitors of other unique targets against candida.     

Ligand enabled none-oxidative decarbonylation of aliphatic aldehydes

Decarbonylation of aldehydes is a basic organic transformation, which has been developed for more than six-decade. However, as comparing to well-studied aromatic aldehydes, fewer examples for catalytic decarbonylation of aliphatic aldehydes were reported, mainly on simple or special substrates. For α-bulky or highly functionalized ones, stoichiometric Rh(I) were usually required for decent yields. Herein, we present a rare example of Ir(I)-catalyzed direct decarbonylation of α-quaternary aldehydes with broad substrate scope and good functional group compatibility via judicious selection of ligand. The α-chirality is memorized in this decarbonylation process. In addition, we report a broad-spectrum decarbonylation of α-secondary and α-tertiary aldehydes containing multifunctional groups with an improved Rh(I)/DPPP recipe. Finally, we realized selective decarbonylation of α-tertiary aldehydes in the presence of α-quaternary one via the reactivity differences.     

Kinetically controlled Ag+-coordinated chiral supramolecular polymerization accompanying a helical inversion

We report kinetically controlled chiral supramolecular polymerization based on ligand–metal complex with a 3 : 2 (L : Ag⁺) stoichiometry accompanying a helical inversion in water. A new family of bipyridine-based ligands (d-L1, l-L1, d-L2, and d-L3) possessing hydrazine and d- or l-alanine moieties at the alkyl chain groups has been designed and synthesized. Interestingly, upon addition of AgNO₃ (0.5–1.3 equiv.) to the d-L1 solution, it generated the aggregate I composed of the d-L1AgNO₃ complex (d-L1 : Ag⁺ = 1 : 1) as the kinetic product with a spherical structure. Then, aggregate I (nanoparticle) was transformed into the aggregate II (supramolecular polymer) based on the (d-L1)₃Ag₂(NO₃)₂ complex as the thermodynamic product with a fiber structure, which led to the helical inversion from the left-handed (M-type) to the right-handed (P-type) helicity accompanying CD amplification. In contrast, the spherical aggregate I (nanoparticle) composed of the d-L1AgNO₃ complex with the left-handed (M-type) helicity formed in the presence of 2.0 equiv. of AgNO₃ and was not additionally changed, which indicated that it was the thermodynamic product. The chiral supramolecular polymer based on (d-L1)₃Ag₂(NO₃)₂ was produced via a nucleation–elongation mechanism with a cooperative pathway. In thermodynamic study, the standard ΔG° and ΔH_e values for the aggregates I and II were calculated using the van''t Hoff plot. The enhanced ΔG° value of the aggregate II compared to that of the formation of aggregate I confirms that aggregate II was thermodynamically more stable. In the kinetic study, the influence of concentration of AgNO₃ confirmed the initial formation of the aggregate I (nanoparticle), which then evolved to the aggregate II (supramolecular polymer). Thus, the concentration of the (d-L1)₃Ag₂(NO₃)₂ complex in the initial state plays a critical role in generating aggregate II (supramolecular polymer). In particular, NO₃⁻ acts as a critical linker and accelerator in the transformation from the aggregate I to the aggregate II. This is the first example of a system for a kinetically controlled chiral supramolecular polymer that is formed via multiple steps with coordination structural change.

The nanoparticles were transformed into the supramolecular polymer as the thermodynamic product, involving a helical inversion from left-handed to right-handed helicity.     

Inhibition of Filamentous Thermosensitive Mutant-Z Protein in Bacillus subtilis by Cyanobacterial Bioactive Compounds

Antibiotic resistance is one of the major growing concerns for public health. Conventional antibiotics act on a few predefined targets and, with time, several bacteria have developed resistance against a large number of antibiotics. The WHO has suggested that antibiotic resistance is at a crisis stage and identification of new antibiotics and targets could be the only approach to bridge the gap. Filamentous Temperature Sensitive-Mutant Z (Fts-Z) is one of the promising and less explored antibiotic targets. It is a highly conserved protein and plays a key role in bacterial cell division by introducing a cytokinetic Z-ring formation. In the present article, the potential of over 165 cyanobacterial compounds with reported antibiotic activity against the catalytic core domain in the Fts-Z protein of the Bacillus subtilis was studied. The identified cyanobacterial compounds were screened using the GLIDE module of Maestro v-2019-2 followed by 100-ns molecular dynamics (MD) simulation. Ranking of the potential compound was performed using dock score and MMGBSA based free energy. The study reported that the docking score of aphanorphine (−6.010 Kcalmol⁻¹) and alpha-dimorphecolic acid (ADMA) (−6.574 Kcalmol⁻¹) showed significant role with respect to the reported potential inhibitor PC190723 (−4.135 Kcalmol⁻¹). A 100 ns MD simulation infers that Fts-Z ADMA complex has a stable conformation throughout the progress of the simulation. Both the compounds, i.e., ADMA and Aphanorphine, were further considered for In-vitro validation by performing anti-bacterial studies against B. subtilis by agar well diffusion method. The results obtained through In-vitro studies confirm that ADMA, a small molecule of cyanobacterial origin, is a potential compound with an antibacterial activity that may act by inhibiting the novel target Fts-Z and could be a great drug candidate for antibiotic development.     

Tailoring of new Ni(II), Hg(II) and UO2(II)–hydrazide complexes: characterization,studies in-vitro and in-silico as well as the Hartree-Fock modeling

A new hydrazide ligand was prepared to synthesize Ni(II), Hg(II) and UO₂(II) complexes, which elucidated by all possible tools. Accordingly, 1M:2L molar ratio was suggested for Ni(II) and Hg(II) complexes, while UO₂(II) complex close to 1:1 ratio. The ligand binds as a bidentate or tridentate mode either as a monobasic via deprotonation of azomethine group or as a neutral with Hg(II) complex. A square-planer geometry was suggested for [Ni(L)₂], while the other complexes reveal octahedral geometry. The antimicrobial screening was performed as well as the antioxidant and cytotoxic activity test towards Ehrlich ascites cells. The ligand and its Ni(II) complex produce a notable inhibition for microorganisms, while their antioxidant and cytotoxicity are up to the standards themselves. The DFT/B3LYP and Hartree-Fock (HF) methods were used to optimize the structures under suitable basis sets to obtain essential parameters and 3D-maps. Utilizing Swiss-ADME link reveals the positive response of the ligand to blood brain barrier and human intestinal absorption. Moreover, other silico tests were performed via Pharmacophore and Molecular Operating Environmental module (MOE) against different proteins. Finally, the agreement between vitro and silico results was noticed with the ligand and its Ni(II)complex.     

Tumor chemical suffocation therapy by dual respiratory inhibitions

The extraordinarily rapid growth of malignant tumors depends heavily on the glucose metabolism by the pathways of glycolysis and mitochondrial oxidative phosphorylation to generate adenosine 5′-triphosphate (ATP) for maintaining cell proliferation and tumor growth. This study reports a tumor chemical suffocation therapeutic strategy by concurrently suppressing both glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) via the co-deliveries of EDTA and rotenone into a glutathione (GSH)-overexpressed tumor microenvironment. EDTA is to block the glycolytic pathway through inhibiting the activity of glycolytic enzymes via the chelation of magnesium ion, a co-worker of glycolytic enzymes, despite the presence of Ca²⁺. Meanwhile rotenone is to inhibit the mitochondrial OXPHOS. This work provides a novel tumor suffocation strategy by the co-deliveries of glucose metabolism inhibitors, especially by de-functioning glycolytic enzymes via eliminating their co-worker magnesium.

The EDTA- and Rotenone-loaded MPER nanoparticles have been synthesized to suffocate tumor cells to death through inhibiting glycolytic process and mitochondrial oxidative phosphorylation simultaneously in vitro and in vivo.     

Mechanically durable biomimetic fibrous membrane with superhydrophobicity and superoleophilicity for aqueous oil separation

Developing an effective and mechanically durable biomimetic membrane for the separation of highly emulsified aqueous oil is significant but challenging owing to its low water flux and serious membrane fouling. In this work, a biomimetic membrane with superhydrophobicity and superoleophilicity was rationally developed via co-electrospinning of polysulfonamide/polyacrylonitrile (PSA/PAN) emulsion solution, followed by decorating of α-Fe₂O₃ nanowire onto the membrane surface to create membrane roughness, and grafting of 1H,1H,2H,2H-perfluorododecyltrichlorosilane (FTCS) to lower membrane surface free energy. Benefiting from the nanowire-wrapped rough membrane structure and the low surface free energy FTCS, the resultant membrane showed superhydrophobicity with a high water contact angle (WCA) of 156°, superoleophilicity with a low oil contact angle (OCA) of 0°, which can separate the highly emulsified aqueous oil with an ultrahigh permeation flux over 7000 L m⁻² h^-1 and high separation efficiency of about 99%. Significantly, the biomimetic membrane also displayed robust stability for long-term separation owing to its advantage of antifouling property, showing great potential applications in large-scale aqueous oil treatment.     

Design,synthesis and preclinical evaluations of (s)-2-((s)-1-benzyl-2,5-dioxopyrrolidin-3-yl)-3-(4-isopropylphenyl)-2-methylpropanal (succ-5) as cardioprotective,hepatoprotective and lipid lowering molecule. in-vivo and in-silico approaches

In this study, the newly synthesized compound (Succ-5) was analyzed through spectral methods, seen for potential receptor targets via molecular docking, and pre-clinically evaluated for therapeutic effects and safety profile using biochemical and histopathological techniques. The biochemical analysis included assessment of cardiac biomarkers, hepatic enzymes, and lipid profiles, while histopathology included evaluation of cardiac and liver tissues. The toxic dose was determined pre-clinically, followed by dividing albino rats into five treatment groups (each having n = 6). The control group received oral saline for eight days. The 5-FU (5-Fluorouracil) group received oral saline for 8 days and 5-FU (150 mg/kg I.P.) on day 5. The atenolol group was administered with atenolol (20 mg/kg) for 8 days and 5-FU (150 mg/kg I.P.) on day 5. Two groups of rats were administered with the test compound (Succ-5) at doses of 5 mg/kg I.P and 10 mg/kg I.P (for 8-days), followed by 5-FU (150 mg/kg I.P.) on day 5. Elevated serum levels of CK-MB (creatinine kinase myocardial band), cTnI (troponin I), LDH (lactate dehydrogenase), lipid profile, and selected liver enzymes including ALP (alkaline phosphatase), ALT (alanine transaminase), AST (aspartate aminotransferase), BT (bilirubin total) and BD (direct bilirubin) were associated with 5-FU toxicity. After administration of the test compound at the mentioned doses, these biomarkers significantly decreased. Likewise, histological examination revealed 5-FU damaged the heart and hepatic tissues, which were also considerably recovered following administration of the test compound. Immunohistochemistry of heart tissue also revealed the low expression of COX-2 and TNF-α in Succ-5 treated groups compared to toxic group. Dose-response evaluation showed that a dose of 10 mg/kg provided better results than 5 mg/kg. The analysis of binding energy values computed via docking simulations showed that Succ-5 interacts with the human beta2-adrenergic G protein-coupled receptor with a slightly stronger affinity than calcium channel T-type. In conclusion, the histological and biochemical findings revealed that the test compound had significant cardioprotective, hepatoprotective, and lipolytic effects in the 5-FU-induced toxicity.     

A temperature-regulated bioorthogonal reaction to target lysine: Hemiacetal pharmacophore in genipin irreversibly binds with UCP2, inhibiting mitochondrial thermogenesis

Mitochondria are essential for eukaryotic life as powerhouses for energy metabolism. Excessive mitochondrial hyperthermia and reactive oxygen species (ROS) production have been associated with aging, cancer, neurodegenerative diseases, and other disorders. Uncoupling protein 2 (UCP2) is the effector responsible for regulating cellular thermogenesis and ROS production via dissipating protons in an electrochemical gradient. A UCP2 inhibitor named genipin (GNP) is being researched for its effect on mitochondrial temperature, but little is known about its mechanisms. This study developed several molecular probes to explore the interactions between GNP and UCP2. The result indicated that the hemiacetal structure in GNP could selectively react with the ɛ-amine of lysine on the UCP2 proton leakage channel through ring-opening condensation at the mitochondrial, cellular, and animal levels. A notable feature of the reaction is its temperature sensitivity and ability to conjugate with UCP2 at high fever as lysine-specific covalent inhibitors that prevent mitochondrial thermogenesis. The result not only clarifies the existence of an antipyretic properties of GNP via its irreversible coupling to UCP2, but also reveals a bioorthogonal reaction of hemiacetal iridoid aglycone for selectively binding with the ɛ-amine of lysine on proteins.     

Partially biobased polymers: The synthesis of polysilylethers via dehydrocoupling catalyzed by an anionic iridium complex

Partially biobased polysilylethers (PSEs) are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex. Different types (AB type or AA and BB type) of monomers are suitable. Levulinic acid (LA) and succinic acid (SA) have been ranked within the top 10 chemicals derived from biomass. BB type monomers (diols) derived from LA and SA have been applied to the synthesis of PSEs. The polymerization reactions employ an air-stable anionic iridium complex bearing a functional bipyridonate ligand as catalyst. Moderate to high yields of polymers with number-average molecular weights (M_n) up to 4.38 × 10⁴ were obtained. A possible catalytic cycle via an Ir-H species is presented. Based on the results of kinetic experiments, apparent activation energy of polymerization in the temperature range of 0–10 °C is about 38.6 kJ/mol. The PSEs synthesized from AA and BB type monomers possess good thermal stability (T₅ = 418 °C to 437 °C) and low glass-transition temperature (T_g = −49.6 °C).     

Synthesis, spectral and thermal studies of N,N − -pyridine-2,6-diyl bis[N −-phenyl(thiourea)] and its metal complexes

Four new metal complexes with the general formula, [ML·mH₂O]nH₂O (where, M = Cu(I), Co(II), Ni(II) or Zn(II); L = N,N ^?-pyridine–2,6-diyl bis[N ^?-phenyl (thiourea)] (PDPT); m = 1 or 3 and n = 0.5 or 4.0), have been synthesized and characterized by elemental analyses, spectral analyses (IR, UV–Vis., ¹H-NMR and MS), thermal analyses (TGA), conductivity and magnetic measurements. The results showed that the ligand (PDPT) acts in a mononegative tridentate manner towards Cu(I) ion coordinating via the two thiol sulfurs and pyridyl nitrogen groups with displacement of only one hydrogen atom from the thiol group, while the ligand behaves in a binegative tridentate manner towards the Co(II), Ni(II) and Zn(II) ions with displacement of two hydrogen atoms from the two thiol groups. The value of magnetic measurements showed a diamagnetic character of the copper complex indicating the reduction of Cu(II) to Cu(I). Semi-empirical calculations of the ligand and its metal complexes have been used to study the molecular geometry using ZINDO/1, PM3 and AM1. Also, the harmonic vibration spectra of the ligand and its metal complexes have been investigated with the purpose to assist the experimental assignment of metal complexes. The results of the optical absorption studies reveal that the optical transition is direct with band gaps energy (E_g) values 2.62, 1.98 and 1.85 eV for Cu, Co and Ni complexes, respectively, indicating that these complexes can behave as semi-conductors.