Alkyl Substitution Research Articles

A Multitarget Approach against Neuroinflammation: Alkyl Substituted Coumarins as Inhibitors of Enzymes Involved in Neurodegeneration.

Neurodegenerative disorders (NDs) include a large range of diseases characterized by neural dysfunction with a multifactorial etiology. The most common NDs are Alzheimer's disease and Parkinson's disease, in which cholinergic and dopaminergic systems are impaired, respectively. Despite different brain regions being affected, oxidative stress and inflammation were found to be common triggers in the pathogenesis and progression of both diseases. By taking advantage of a multi-target approach, in this work we explored alkyl substituted coumarins as neuroprotective agents, capable to reduce oxidative stress and inflammation by inhibiting enzymes involved in neurodegeneration, among which are Carbonic Anhydrases (CAs), Monoamine Oxidases (MAOs), and Cholinesterases (ChEs). The compounds were synthesized and profiled against the three targeted enzymes. The binding mode of the most promising compounds (7 and 9) within MAO-A and -B was analyzed through molecular modeling studies, providing and explanation for the different selectivities observed for the MAO isoforms. In vitro biological studies using LPS-stimulated rat astrocytes showed that some compounds were able to counteract the oxidative stress-induced neuroinflammation and hamper interleukin-6 secretion, confirming the success of this multitarget approach.

Synthesis of sulfhydryl‐functionalized polymers for the efficient adsorption of Pd2+ and Ag+ from aqueous solution

AbstractHerein, two sulfhydryl‐functionalized polymers, namely, EDT‐HCPS and TMPMP‐HCPS, were synthesized according to the Friedel‐Craft s alkylation and nucleophilic substitution, and they were used to adsorb Pd2+ and Ag+ from aqueous solution. The Friedel‐Crafts alkylation offered the polymers with hyper‐cross‐linking frameworks composed of plentiful rigid methylene. The nucleophilic substitution brought abundant functional SH groups (the sulfur contents were 12.6 and 9.4 wt%, respectively) to the polymers. The adsorption results showed that the capacities of Pd2+ and Ag+ on EDT‐HCPS were larger than TMPMP‐HCPS, and the higher quantities of functional SH groups and the porosity played a beneficial role. The equilibrium data can be characterized by the Langmuir model, and the maximum capacities of Pd2+ and Ag+ on EDT‐HCPS at 308 K were predicted to be 383.92 and 212.93 mg g−1, respectively. The produced polymers represented superior adsorption selectivity, reproducibility, and reusability, demonstrating their excellent performance for the adsorption of Pd2+ and Ag+, and analysis of the adsorption mechanism demonstrated that the SH groups played a major role due to the strong chemical complexation of the functional SH with Pd2+/Ag+.

Theoretical Insight into the Imidazolium-Based Ionic Liquid Interface Structure and Differential Capacitance on Au(111): Effects of the Cationic Substituent Group.

Electric double layers (EDLs) play a key role in the electrochemical and energy storage of supercapacitors. It is important to understand the structure and properties of EDLs. In this work, quantum chemical calculations and molecular dynamics (MD) simulations are used to study the microstructure of EDLs of four different substituents of imidazolium-based bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) on the Au(111) surface. It is shown that the particle interactions influence the different arrangements of the anion and cation. More alkyl substitutions and longer alkyl chains result in a higher ELUMO and thus a stronger interaction energy between cations and electrodes. Strong interactions produce linear patterns of anions/cations on the electrode and a maximum value of differential capacitance near PZC, whereas weak interactions generate worm-like patterns of anions/cations on Au(111) and a minimum value of differential capacitance near the PZC. We hold the opinion that the alkyl substitution has more effects on the EDLs. Our analysis provides a new perspective on EDLs structures at the atomic and molecular level. This study provides a good basis and guidance for further understanding the interface phenomena and characteristics of ionic liquids in electrochemical and energy device applications.

Alkyl Chains Modulated Magnetization Dynamics of Mononuclear Trigonal Prismatic CoII Complexes.

Four benzeneboron-capped mononuclear CoII complexes with different alkyl substitutions on the fourth position of phenylboronic acid were obtained. The CoII ions are all wrapped by the pocket-like ligands and located in trigonal prismatic coordination geometries. Alternating-current magnetic susceptibility measurements reveal that they show different magnetization dynamics, such as distinct relaxation rates at the same temperature, the faster QTM rates for the ethyl and propyl substituted complexes, as well as different relaxation processes. Magneto-structural correlation study reveals that the various deviations of coordination geometry of CoII ion, diverse crystal packings and possible different vibration modes of substituents caused by modifying alkyl chains are the key factors affecting the magnetization dynamics. This work demonstrates that the alkyl chains even locating far away from the metal center can have a large impact on the magnetic behavior of the CoII complex with a very rigid coordination geometry, offering a new perspective towards transition metal based single-molecule magnets.

Gossypetin Is a Novel Modulator of Inflammatory Cytokine Production and a Suppressor of Osteosarcoma Cell Growth.

Osteosarcoma (OS) is a common childhood sarcoma, and its treatment is hindered by adverse effects, chemoresistance, and recurrence. Interleukin (IL)-6 production by tumors plays a significant role in inflammation, carcinogenesis, and metastasis. This study aimed to investigate the antiproliferative potential of luteolin derivatives in OS and to evaluate interleukin production. MG-63, Saos-2, HOS, and 143B human OS cell lines were incubated with luteolin and eight derivatives containing hydroxy, chlorine, or alkyl substitutions. The cell viability and growth were evaluated in the presence of these compounds. Apoptosis was also examined through the analysis of the Bax expression and caspase-3 activity. Finally, the gossypetin effects were measured regarding the production of proinflammatory cytokines interleukin (IL)-6, IL-1β, and IL-12p70. Our findings show that gossypetin was the most potent compound, with proliferation-suppressing activities that induced a series of critical events, including the inhibition of the cell viability and growth. Apoptosis was associated with enhanced caspase-3 activity and increased Bax expression, indicating the involvement of the intrinsic pathway of apoptosis. Moreover, pre-/co-treatment with gossypetin significantly reduced the autocrine production of proinflammatory cytokines. Further investigation is required; nevertheless, considering the link between inflammation, carcinogenesis, and metastasis in OS, our findings suggest that gossypetin exhibits anti-proliferative and anti-inflammatory properties that are potentially relevant in the clinical context.

Substituent Dependence on the Reactions of Criegee Intermediates with Carbon Dioxide and Carbon Monoxide.

Criegee intermediates (CIs), R1 R2 COO, are active molecules produced in the atmosphere from the ozonolysis of alkenes. Here, we systematically evaluated the reactivity of ten CIs with carbon monoxide and carbon dioxide using CCSD(T)-F12/cc-pVTZ-F12//B3LYP/6-311+G(2d,2p) energies and transition state theory. Many previous studies focused on alkyl substitution, but here we evaluated both alkyl and vinyl substitution toward the reactivity by studying five anti-type CIs: CH2 OO, anti-CH3 CHOO, anti-cis-C2 H5 CHOO, anti-trans-MACRO, anti-cis-MACRO; and five syn-type CIs: syn-CH3 CHOO, (CH3 )2 COO, syn-trans-C2 H5 CHOO, syn-trans-MVKO, and syn-cis-MVKO. Our study showed that reactions involving CO2 have a large substituent dependence varying nearly five orders of magnitude, while those involving CO have a much smaller two orders of magnitude difference. Analysis based on the strain interaction model showed that deformation of the CI is an important feature in determining the reactivity with CO2 . On the other hand, we used the OO and CO bond ratios to analyze the zwitterionic character of the CIs. We found that vinyl substitution with π-conjugation results in smaller zwitterionic character and lower reactivity with CO. Lastly, the reactivity of CIs with CO as well as CO2 were found to be not fast enough to be important in an atmospheric context.

High Energy Density Porous RuO2 micro-Supercapacitors Using Protic Ionic Liquid Electrolytes

The rapid development of the Internet of Things (IoT) demands reliable and long-term energy supply to microelectronic devices distributed over the network with high power performance and less maintenance required.[1] Micro-supercapacitors (MSCs) have come to the foreground as miniaturized energy storage devices showing outstanding power density and long cycle life. However, the low cell voltage and low energy density remain major bottleneck that prevents their adoption in real device applications. To this end, several studies have been devoted to the engineering of MSC electrode materials and structural architecting of current collectors within the limited available footprint. This approach could offer opportunities to enhance the electrochemically active surface and mass loading of active materials with fast ion diffusion kinetics, leading to high areal energy density performance.[2] Although several efforts have been put forth in this direction, the complex synthesis route, unfavourable interfacial and mechanical stability of the electrode, electrolyte compatibility issues, etc. remain an arduous challenge.[3] The low cell voltage is another major issue preventing from achieving high energy density values in MSCs as it is directly linked to the electrochemical stability window (ESW) of the electrolytes used.[4] In addition, liquid-state electrolytes currently employed are inappropriate for the microfabrication route as it is prone to evaporation, leakage, and potential safety issues. Hence, a lot of research attention has been given to developing solid-state electrolytes able to afford large operational windows and help promote the application of on-chip MSCs. In this work, we have demonstrated the use of protic ionic liquid (PIL)-based electrolytes able to provide pseudocapacitance in hydrous ruthenium dioxide (RuO2) electrodeposited on interdigitated MSC substrates with extended operational cell voltage. As a pseudocapacitive material, RuO2 exhibits excellent conductivity, high electrochemical reversibility, and cycling stability.[5] On the other hand, as room temperature molten salts, PILs help to overcome evaporation and encapsulation problems associated with the conventional aqueous electrolytes and flammability and safety issues linked to common organic electrolytes.[6-9] We explored pyrrolidinium-based PILs with varying alkyl substitutions, their structure-property, and electrochemical studies for RuO2 MSCs. To further expand the use of these PILs in real devices, 3D MSCs with higher active material mass loading was realised using interdigitated porous Au current collector substrates. The PIL-based porous RuO2 MSCs showed superior charge storage and higher energy density performance as compared to conventional aqueous electrolytes. To envision the practical application of RuO2 MSCs and their subsequent integration with microelectronic devices, ionogel-based solid-state electrolytes were developed. This work opens pathways to develop micro-supercapacitors exhibiting high energy and power density by combining pseudocapacitive metal oxide-based active materials and protic ionic-liquid-based non-aqueous electrolytes and help their integration with on-chip IoT devices.

Helical Polycyclic Heteroaromatic as Hole Transport Material for Perovskite Solar Cell: Remarkable Impact of Alkyl Substitution Position

AbstractPolycyclic aromatic hydrocarbons play a critical role in the development of organic semiconductors. This study unravels the impact of alkyl substitution position on the molecular energy level, glass transition temperature, diffusion of external species, and hole transport of a pyrrole‐rich, helical polycyclic heteroaromatic, that is TBPC. Compared to terminal substitution, internal hexyl substitution results in steric repulsion with TBPC, weakening π─π stacking and therefore improving thin film morphology. Internal substitution also reduces energy disorder, lowers reorganization energy, and increases intermolecular transfer integrals, leading to enhanced hole mobility. Notably, the organic semiconductor with internal hexyl substitution (TBPC‐611) exhibits a higher molecular packing density, resulting in a markedly higher glass transition temperature and slower diffusion of external species. Using TBPC‐611 as the hole transport material, this work successfully fabricates perovskite solar cells with an average power conversion efficiency above 24%, showing good photostability and thermostability. These findings contribute new insights to the development of high‐performance organic semiconductors.

Aqueous Polyelectrolyte Electrodeposition: The Effects of Alkyl Substitution and Varying Supporting Electrolyte Concentrations on the Deposition Efficiency

AbstractThe controlled growth of surface‐modifying polymer films by electrodeposition often fails because of the lack of redox activity of these compounds. Here, electroactive complexants help to electrodeposit non‐electroactive polymers. Hence, we investigate the counterion‐induced electrodeposition of polyelectrolytes: three quaternized poly(N,N‐dialkylaminoethyl methacrylate)s (qPDAAEMA), in particular their methyl, ethyl, and isopropyl derivatives (i. e. qPDMAEMA, qPDEAEMA, and qPDPAEMA), provide transparent solutions in the presence of hexacyanoferrate(II) (ferrocyanide) at specific concentration windows of the KCl supporting electrolyte. Below a certain KCl concentration, insolubility dominates irrespective of the hexacyanoferrate valency, whilst above an upper threshold, full solubility is observed. Between these limits, oxidation reversibly electrodeposits polymer/hexacyanoferrate(III) (ferricyanide) complexes. Hydrodynamic voltammetry (and data analysis using in‐house software) provides access to the deposition efficiency (DE). qPDEAEMA with ethyl substituents shows highest DEs; larger or smaller substituents fall short because of a balance between “hydrophobicity” and charge separation, shifting the window toward smaller salt concentrations with increasing alkyl size. We always observe a DE maximum close to the minimum salt concentration, whilst electrochemical quartz crystal microbalance (EQCM) measurements indicate a change in film water content close to the maximum. These effects, being also discussed in terms of polymer conformation, can direct the future engineering of electroassisted coatings.

Synthesis of hyperbranched polyethylene and carboxylate functionalized polyethylene using bis(benzocyclopentyl) α-diimine Pd(II) catalysts with axial substituent-constrained strategy

Preparation of hyperbranched polyethylene and its polar functionalized polyethylene by chain walking polymerization technology is convenient and efficient. In this work, two bis(benzocyclopentyl) α-diimine ligands with different backbones and the corresponding Pd(II) catalysts were designed and synthesized. The axially open palladium catalysts enabled the polymerization of ethylene to afford hyperbranched polyethylene with low molecular weights (2.58–8.21 kg/mol) and high branching densities (111–142/1000C). Moreover, hyperbranched E-MA copolymers with high MA incorporation ratios (up to 20.7 mol%) were obtained by copolymerization of ethylene with MA using these Pd(II) catalysts. In addition, the polyethylene and E-MA copolymers obtained from the catalyst with butyl backbone exhibited significantly higher molecular weights with remarkably higher catalytic activities compared to those obtained from the acenaphthene backbone catalyst. Most interestingly, the axial substituent-constrained strategy of o-aryl bis(benzocyclopentyl) substituents provides a more open axial space, facilitating the insertion of methyl acrylate, and the formation of branching, compared to the conventional chain o-aryl alkyl substitution.

Novel 1,4 benzothiazine 3-one derivatives as anticonvulsant agents: Design, synthesis, biological evaluation and computational studies

In this study, two series of novel 1,4-benzothiazine-3-one derivatives with alkyl substitution (series 1: 4a-4f) and aryl substitution (series 2: 4g-4l) were designed and synthesized based on the chemical scaffolds of perampanel, hydantoins, progabide and etifoxine as anti-convulsant agents. The chemical structures of the synthesized compounds were confirmed by FT-IR, 1H NMR and 13C NMR spectroscopy. Anti-convulsant effect of the compounds was examined through intraperitoneal pentylenetetrazol (i.p. PTZ) induced epilepsy mouse models. Compound 4h (4-(4-bromo-benzyl)− 4 H-benzo[b] [1,4] thiazin-3(4 H)-one) demonstrated a promising activity toward chemically-induced seizure experiment. Molecular dynamics simulation on GABA-Aergic receptors as a plausible mechanism were also done to achieve the binding and orientation of compounds in the active site of the target to evaluate the results of docking and experimental studies. The computational results were confirmed the biological activity. DFT study of 4c and 4h was performed on B3LYP/6–311 G** level of theory. Reactivity descriptors such as HOMO, LUMO, electron affinity, ionization potential, chemical potential, hardness and softness were studied in detail and show that 4h has higher activity than 4c. Also, the frequency calculations were performed on the same level of theory and the results are in line with experimental data. Moreover, in silico ADMET properties were done to establish a relationship between the physiochemical data of the designed compounds and their in-vivo activity. Appropriate plasma protein binding and high blood-brain barrier penetration are the main features of desired in-vivo performance.

Chalcone derivatives as novel, potent and selective inhibitors against human Notum: Structure–activity relationships and biological evaluations

Human Notum (hNotum) inhibitors could be used for treating Wnt signalling-associated diseases including colorectal cancer. Herein, two series of chalcone derivatives were designed and synthesized aiming to find selective and potent hNotum inhibitors. Structure–activity relationship (SAR) studies showed that 2-methoxyl and 5-bromine substitutions on A-ring significantly enhanced anti-hNotum effect, while 4′-ethoxyl and 3′-alkyl substitutions on B-ring were beneficial for hNotum inhibition. Among all tested chalcones, B11 displayed the most potent anti-Notum effect (IC50 = 3.6 nmol/L), good selectivity, excellent chemical stability and suitable metabolic stability. Further investigations showed that B11 acted as a competitive inhibitor of hNotum, while this agent (5 µmol/L) significantly weaken the migration abilities of colorectal cancer cells. Collectively, this study deciphers the SARs of chalcones as hNotum inhibitors and reports a novel and potent hNotum inhibitor with the anti-migration effect on colorectal cancer cells, which offers a promising lead compound to develop novel anti-cancer agents.

Interactive Organic Reaction Trajectory Animation iPhone Application (iORA) and Web Site (webORA)

Organic reaction trajectories show atomic motion and molecular reorganization of reactants during a single product-forming collision. iORA is a free (available from the Apple App Store), easy to use, highly interactive iPhone application that provides on-the-fly 3D rendering of organic reaction trajectories calculated with density functional theory (DFT) direct dynamics simulations. Visualization of trajectories using iORA enables qualitative and quantitative learning about organic reaction pathways. iORA users can interactively zoom, rotate, and translate the reaction animations. Users can track distances, angles, and dihedral angles. Other iORA features include buttons to jump to the transition state, control the animation speed, and 3D image display. Currently available reaction classes include Bronsted acid–base, alkyl substitution, alkene addition, alkyne addition, diene addition, rearrangement, oxidation, reduction, carbonyl addition, radical, pericyclic, and aromatic substitution. WebORA is a web-based site that also displays interactive DFT-based organic reaction trajectory simulations from these reaction classes. It can be used by all web browsers and operating systems. iORA and webORA also offer brief trajectory descriptions.

Structure and nuclear quadrupole coupling interaction in hydroxylamines: The rotational spectrum of N,N-diethyl(2H)hydroxylamine

The ground-state rotational spectrum of N,N-diethyl(2H)hydroxylamine (C2H5-NOD-C2H5) was measured by Fourier transform microwave spectroscopy. Six rotational transition lines were assigned to the most stable conformer with the alkyl chain in the trans arrangement and the hydroxyl trans to the bisector of the CNC angle, that is, with the NOD frame in the bc-symmetry plane. Rotational constants are A= 7210.938(2), B= 2018.628(1), and C= 1739.696(1) MHz. These data together with those previously determined for the parent species and 13C and 15N isotopologues, were used to determine a partial r0 structure. The hyperfine structure due to the nuclear quadrupole coupling (NQC) interaction of both 14N and D nuclei was disentangled allowing to obtain the diagonal NQC-constants. On the basis of the determined geometry, the NQC-tensor values in the electric field-gradient principal axis system were determined (χxxN= 0.71, χyyN= 5.90, χzzN= −6.61 MHz; χxxD= −0.11, χyyD= −0.15, χzzD= 0.26 MHz). Comparison with other amines shows that using ammonia as reference, χzzN can be estimated with an additive model: +0.4 and +1.7 MHz from hydrogen to alkyl and hydroxyl substitution, respectively. From the analysis of the available data on the 1:1 water complex of N,N-diethylhydroxylamine, a 8% electric field gradient decrease at the nitrogen nucleus due to the formation of the hydrogen bond involving the nitrogen lone pair was found.

Elucidation of Structure–Function Relationships of Hyaluronic Acid-Based Polymers via Combinatorial Approaches

Hydrogels have been identified as biomaterials of significant interest owing to their unique properties─hydrophilic structures, high degree of structural flexibility, low toxicity, biocompatibility─that qualify them as ideal candidates in a wide range of biomedical and pharmaceutical applications from wound dressing surface coatings, to drug delivery composites, and tissue scaffolds. However, such desired properties of hydrogels simultaneously endow these materials with inherent shortcomings that have hindered their prolific implementation in even more industrial applications; specifically, hydrogels suffer from low mechanical stability and loss of native function upon exposure to industrial solvents. One proposed technique to overcome these challenges and thus functionalize hydrogels to increased their wider range of industrial applications is their chemical modification to elicit controllable changes in their structure and function to thus fulfill the user-defined end goal. The chemical modification strategy further drives the need for an in-depth understanding of the physical and chemical phenomena that control the assembly of modified biopolymers and thus determine their functionality. We hypothesize that a combinatorial approach employing both molecular dynamics (MD) simulations and analytical techniques could be used to probe the self-assembly of alkyl chain-modified hyaluronic acid (HYA)─model biopolymer chosen for its hydrophilicity, relative abundance, biocompatibility, and periodic carboxylate reactive group─and thus will allow us to control the assembly dynamics and its end structure properties when alkyl-chain-modified HYA networks are to be constructed, especially porosity, average pore aperture size, and accessible surface area. For this purpose, modified HYA chains were synthesized via (1)-ethyl-3-(3-dimethylaminopropyl) carbodiimide chloride (EDC)-mediated amine group attachment of dodecylamine to the periodic carboxylate group onto the HYA backbone. Material characterization including Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis was conducted to confirm the expected EDC reaction chemistry and further assess the water uptake capacity of the resulting modified hydrogels. MD simulations of both unmodified HYA and modified HYA chains─with varied lengths of attached alkyl groups as well as varied degrees of alkyl group substitution on the HYA backbone─were carried out to analyze the self-assembly dynamics of such chains and thus determine how differences in chemical modification eventuate the critical differences in the end structure properties of the resulting networks. Our findings demonstrate that targeted, atomic-level investigation and corroborated analytical analyses of the assembly of chemically modified hydrogels are necessary to develop the next generation of fully optimized biomaterials that have extended applicability in industrial settings.

Type-I Hemins and Free Porphyrins from a Western Australian Sponge Isabela sp.

Two novel free porphyrins, isabellins A and B, as well as the known compounds corallistin D and deuteroporphyrin IX were isolated from a marine sponge Isabela sp. LC-MS analysis of the crude extract revealed that the natural products were present both as free porphyrins and iron(III) coordinated hemins, designated isabellihemin A, isabellihemin B, corallistihemin D and deuterohemin IX, respectively. Structures were determined via high-resolution mass spectrometry, UV-Vis spectroscopy and extensive NOESY NMR spectroscopic experiments. The type-I alkyl substitution pattern of isabellin A and isabellihemin A was assigned unambiguously by single crystal X-ray diffraction. Biological evaluation of the metabolites revealed potent cytotoxicity for isabellin A against the NS-1 murine myeloma cell line.

Synthesis and immunopharmacological evaluation of novel TLR7 agonistic triazole tethered imidazoquinolines.

Toll-like receptors-7 and -8 are expressed abundantly on antigen-presenting cells, and their agonists make potential adjuvant candidates for the development of new efficacious vaccines. In view of the importance of new efficacious imidazoquinoline based adjuvants, herein we have synthesized a focused library of a new class of imidazoquinolines retaining the N-isobutyl substitution of an imidazole moiety as in imiquimod and introduced a 1,2,3-triazolyl moiety upon alkyl substitution at the imidazolemethyne carbon employing triazolyl click chemistry. All the novel analogues were characterized using various spectroscopic techniques and the target specificity of these molecules was determined using HEK TLR7/8 transfected cell lines. TLR7/8 activity and also the molecular docking results correlated primarily to the position of the substituent for aromatic groups and also to the chain length in alkyl substitutions. The immunomodulatory properties of these analogues were evaluated using murine DC activation and also with hPBMC activation markers, cytokines which revealed that these analogues after modification were able to target the TLR7 receptors and also had a pro-inflammatory immune response.

Simple magnesium alkoxides: synthesis, molecular structure, and catalytic behaviour in the ring-opening polymerization of lactide and macrolactones and in the copolymerization of maleic anhydride and propylene oxide.

The synthesis of two chiral bulky alkoxide pro-ligands, 1-adamantyl-tert-butylphenylmethanol HOCAdtBuPh and 1-adamantylmethylphenylmethanol HOCAdMePh, is reported and their coordination chemistry with magnesium(II) is described and compared with the coordination chemistry of the previously reported achiral bulky alkoxide pro-ligand HOCtBu2Ph. Treatment of n-butyl-sec-butylmagnesium with two equivalents of the racemic mixture of HOCAdtBuPh led selectively to the formation of the mononuclear bis(alkoxide) complex Mg(OCAdtBuPh)2(THF)2. 1H NMR spectroscopy and X-ray crystallography suggested the selective formation of the C2-symmetric homochiral diastereomer Mg(OCRAdtBuPh)2(THF)2/Mg(OCSAdtBuPh)2(THF)2. In contrast, the less sterically encumbered HOCAdMePh led to the formation of dinuclear products indicating only partial alkyl group substitution. The mononuclear Mg(OCAdtBuPh)2(THF)2 complex was tested as a catalyst in different reactions for the synthesis of polyesters. In the ROP of lactide, Mg(OCAdtBuPh)2(THF)2 demonstrated very high activity, higher than that shown by Mg(OCtBu2Ph)2(THF)2, although with moderate control degrees. Both Mg(OCAdtBuPh)2(THF)2 and Mg(OCtBu2Ph)2(THF)2 were found to be very effective in the polymerization of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) also under mild reaction conditions that are generally prohibitive for these substrates. The same catalysts demonstrated efficient ring-opening copolymerization (ROCOP) of propylene oxide (PO) and maleic anhydride (MA) to produce poly(propylene maleate).

Effect of pyrrole substitution on the optical limiting properties of 3,5-distyrylBODIPYdyes

The optical limiting properties of three meso-pyridyl-distyrylBODIPY dyes with differing alkyl substitution patterns at the 2,6- and 1,7-positions on the pyrrole moieties are investigated. Styryl groups are introduced at the 3,5-positions to form dyes with strong donor-[Formula: see text]-acceptor (D-[Formula: see text]-A) properties. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability obtained for a dye that is unsubstituted at both the 2,6- and 1,7-positions suggesting that the optical limiting properties are enhanced when the meso-aryl ring can freely rotate into the plane of the BODIPY core.

Alkyl-phenanthrenes in early life stage fish: differential toxicity in Atlantic haddock (Melanogrammus aeglefinus) embryos.

Tricyclic polycyclic aromatic hydrocarbons (PAHs) are believed to be the primary toxic components of crude oil. Such compounds including phenanthrene are known to have direct effects on cardiac tissue, which lead to malformations during organogenesis in early life stage fish. We tested a suite of 13 alkyl-phenanthrenes to compare uptake and developmental toxicity in early life stage haddock (Melanogrammus aeglefinus) embryos during gastrulation/organogenesis beginning at 2 days post fertilization via passive dosing. The alkyl-phenanthrenes were tested at their solubility limits, and three of them also at lower concentrations. Measured body burdens were linearly related to measured water concentrations. All compounds elicited one or more significant morphological defects or functional impairment, such as decreased length, smaller eye area, shorter jaw length, and increased incidence of body axis deformities and eye deformities. The profile of developmental toxicities appeared unrelated to the position of alkyl substitution, and gene expression of cytochrome 1 a (cyp1a) was low regardless of alkylation. Mortality and sublethal effects were observed below the expected range for baseline toxicity, thus indicating excess toxicity. Additionally, PAH concentrations that resulted in toxic effects here were far greater than when measured in whole crude oil exposures that cause toxicity. This work demonstrates that, while these phenanthrenes are toxic to early life stage fish, they cannot individually account for most of the developmental toxicity of crude oil, and that other compounds and/or mixture effects should be given more consideration.