Mechanical and physicochemical properties of matrices for fiber reinforced plastics based on low-melting phthalonitrile monomers

The mechanical properties of cured phthalonitrile matrices for fiber reinforced plastics (FRP) based on low-melting phenylmethylsilanediyl-bis[oxymethylene(1,4-phenylene-4’-oxyphthalodinitrile)] (1) or its mixture with 1,3-phenylene-bis(oxy-4-phthalodinitrile) (2, comonomer) were studied. The flexural strength, Young’s modulus, fracture toughness, and some other characteristics of the cured resins based on monomer 1 (PN-1) and the mixture of monomers 1 and 2 (PN-1m) were determined. It is noted that the PN-1 resin can be processed by vacuum infusion and the PN-1m resin can be processed by compression injection molding. The developed resins are promising as materials for high-tech aerospace applications.     

Ring-opening polymerization of ε-caprolactone catalysed by (pyridyl)benzoazole Zn(II) and Cu(II) complexes

This paper describes the synthesis of (pyridyl)benzoazole Zn(II) and Cu(II) complexes and their applications as catalysts in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). Reactions of 2-(3-pyridyl)-1H-benzimidazole (L1), 2-(2-pyridyl)-1H-benzothiazole (L2) and 2-(2-pyridyl)-1H-benzimidazole (L3) with Zn(II) and Cu(II) acetates produced the corresponding complexes; [Zn₂(L1)₂(OAc)₄)] (1), [Cu₂(L1)₂(OAc)₄] (2), [Zn(L2)(OAc)₂)] (3), [Zn(L3)(OAc)₂)] (4) and [Cu(L3), (OAc)₂)] (5). Molecular structures of complexes 2 and 5a revealed that while L1 adopts a monodentate binding mode, through the pyridyl nitrogen atom, L3 exhibits a bidentate coordination mode. All the complexes formed active catalysts in the ROP of ε-CL to afford moderate molecular weight polymers. The kinetics of the ROP reactions of ε-CL were pseudo-first-order with respect to monomer and catalysts.     

Separation and Identification of Lutein Derivatives in Processed Foods

In the present work, we show that in processed sorrel, the lutein (1) can convert to 3’-epilutein (2) – 3’-stereoisomer of lutein – by epimerisation reaction, as well as to anhydrolutein I (3) and II (4) by dehydration reaction. The newly formed anhydrolutein I (3) and II (4) were detected and identified by HPLC-DAD and HPLC-MS techniques and co-chromatography with authentic samples. The compounds 1 and 2 were also isolated from cooked sorrel by column chromatography and characterized by NMR spectroscopy.     

Study of lithium complexes with benzo-15-crown-5 ether by X-ray diffraction and IR spectroscopy

The complex formation of lithium with benzo-15-crown-5 (B15C5) was investigated. The complexes LiB15C5H₂OX, where X = Cl^? (1), I^? (2), (3), (5), and LiBF₄B15C5 (4) were synthesized and studied by IR spectroscopy. Complexes 1–4 were examined by X-ray diffraction. According to IR spectroscopy data, the crown ether conformation changes upon dissolution. The interaction of the extracted complex with the solvent was identified.     

Crystal structures of the polymer copper(II) complexes with acylhydrazones of bromosalicylaldehyde derivatives

Polymer copper(II) complexes with 5-bromosalicylaldehyde heptanoylhydrazone (I) and 3,5-dibromosalicylaldehyde acetylhydrazone (II) are synthesized and structurally characterized. In complex I, the formation of the polymer is due to the coordination of the hydrazide nitrogen atom to the copper(II) ion of the adjacent fragment. In complex II, polymer formation is due to the binding of the monomer fragments by dipyridyl linkers (CIF files CCDC 947908 (I) and 947909 (II)).     

Supramolecular systems formed by calix[4]resorcinarenes and surfactants in chlorophorm

Capacity titration and ¹H NOESY 2D NMR were applied to investigation of intermolecular interactions and aggregation of amphiphilic calix[4]resorcinarenes (CRA 1, 2) modified with 1,2,4-triazine (1) and oxazine (2) functions in chloroform in the presence of cationic (3) and non-ionic (4) surfactants (SAA). Critical concentrations of micelle formation (CMC) indicate that the ability of CRA 1, 2 to form supramolecular aggregates like micelles or hybrid micelles with SAA 3, 4 only weakly depends on the constitution of CRA functional groups. In the case of the hybrid micelles, when CMC are defined by the nature of surfactants 3 or 4, the methyl and methylene groups of the hydrophobic fragments (CRA 1, 2) were found to interact with the hydroxy groups of SAA 3 and ethylene oxide moieties of SAA 4.     

Regioselective Friedel–Crafts deacylations of polycyclic aromatic ketones in the pyrene series

1,3,6,8-tetrabenzoylpyrene (1,3,6,8-Bz ₄ PY) and 1,3,6-tribenzoylpyrene (1,3,6-Bz ₃ PY) were synthesized and their crystal structures were determined. The Friedel–Crafts deacylations in PPA of 1,3,6,8-Bz ₄ PY (at 120–200 °C) and of 1,3,6-Bz ₃ PY (at 80–160 °C) have been studied. The mono-deacylation of 1,3,6-Bz ₃ PY was regioselective and led to three dibenzoylpyrenes in the following order of relative amounts: 1,8-Bz ₂ PY > 1,6-Bz ₂ PY > 1,3-Bz ₂ PY. 1,3,6,8-Bz ₄ PY was resistant to deacylation at 120–160 °C. The deacylations of 1,3,6,8-Bz ₄ PY at 200 °C gave the polycyclic aromatic ketone (PAK) 8H-dibenzo[def,qr]chrysen-8-one (DBCO) via an intramolecular Scholl reaction. Two plausible pathways of the Friedel–Crafts deacylation of 1,3,6,8-Bz ₄ PY to give DBCO are proposed. A density functional theory (DFT) B3LYP/6-311(d,p) computational study of the conformational spaces of 1,3,6-Bz ₃ PY and 1,3,6,8-Bz ₄ PY was performed. The estimated energy barriers of formation of dibenzoylpyrenes by deacylation of 1,3,6-Bz ₃ PY increase in the following order: 1,8-Bz ₂ PY < 1,3-Bz ₂ PY < 1,6-Bz ₂ PY. A mechanism of the Friedel–Crafts deacylation of 1,3,6-Bz ₃ PY in PPA via the respective O-protonated ketone and σ-complexes is presented.     

Transition metal complexes of a hydrazone derived from hydralazine hydrochloride and 3,5-di-tert-butylsalicylaldehyde

Mononuclear Co(III), Ni(II) and Cu(II) coordination compounds of (E)-1-(3,5-di-tert-butyl-2-hydroxybenzylidene)-2-(phthalazin-1-yl)hydrazine (LH) were prepared and characterized by physicochemical and spectroscopic methods. The metal-to-ligand ratio was found to be 1:2 in [Co(L)₂]Cl·2H₂O (1) and [Ni(L)₂]·2H₂O (2), while it is 1:1 in [Cu(L)Cl]·2CH₃OH (3). The X-ray crystal structures of LH and complex 1 is are reported. LH shows monobasic behavior, coordinating through NNO donor atoms. The complexes were investigated for their antimicrobial properties. Complexes 1 and 3 show excellent antibacterial and antifungal activities, respectively.     

The synthesis and structural characterization of transition metal coordination complexes of coumarilic acid

The coumarilate (coum^?) complexes of Co^II(1), Ni^II(2) Cu^II(3) and Zn^II(4) were synthesized and characterized by elemental analysis, magnetic susceptibility, solid-state UV–Vis, FTIR spectra, thermoanalytical TG–DTG/DTA and single-crystal X-ray diffraction methods. It was found that all of the complex structures have 2 mol (coum^?) ligand bonded as monoanionic monodentate in the structures of 1 and 2 while they were coordinated to metal cations as monoanionic bidentate in the complexes 3 and 4. There was not any hydrate water in the metal complexes. The complexes of 1 and 2 have four moles of aqua ligand, and the other complexes have two moles. Thermal decomposition of each complex starts with dehydration, and then the decomposition of organic parts goes. The thermal dehydration of the complexes takes place in one (for the compounds of 2, 3, 4) or two (for the compound 1) steps. The decomposition mechanism and the thermal stability of the complexes under investigation were determined on the basis of their structures. Metal oxides were obtained as the final decomposition product.     

Synthesis and anticancer activities of 1,4-phenylene-bis-<Emphasis Type="Italic">N</Emphasis>-acetyl- and <Emphasis Type="Italic">N</Emphasis>-phenylpyrazoline derivatives

Novel 1,4-phenylene-bis-N-acetyl- (3a–h) and bis-N-phenylpyrazoline derivatives (4a–h) were obtained by addition of hydrazine hydrate and phenylhydrazine to bis-chalcone derivatives (1a–h) in acetic acid and acetic acid/ethanol for 4 and 8 h in reflux conditions, respectively. The structures of the obtained bis-N-acetylpyrazoline and bis-N-phenylpyrazoline derivatives were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic methods and elemental analysis. Compounds 3a–h and 4a–h were investigated to evaluate their anticancer activities against C6 (rat brain tumor cells) and HeLa (human uterus carcinoma) in vitro using a dose-dependent assay from 5 to 100 μM with 5-fluorouracil (5-FU) as standard anticancer drug. Compound 3a showed higher cell-selective activity compared with 5-FU against HeLa cells. Compounds 3a–h (except 3d) were shown to have better activities than 5-FU against both cells, particularly at high concentration. Compound 4c showed higher cell-selective activity compared with 5-FU against C6 cells. Compound 3a may be particularly promising as an anticancer drug against HeLa cells.     

Synthesis of New Pyrano[2,3-<Emphasis Type="Italic">d</Emphasis>]Pyrazoles and Furochromones Derivatives Utilizing Amino Acids Derivatives

Hydrolysis of oxazolone derivatives (2b) yielded α-khellinoyl(amino)-cinnamic acid (3) as a good precursor to react with ethyl esters of glycine, L-methionine, and glycylglycine affording 4, 5, and 4, 5 respectively with minor product 7. Hydrolysis of oxazolone derivatives (2b) afforded α,β-dehydroamino acid derivatives (DDAA) (8). Interaction of oxazolone derivatives (2a,b) with active methylene compounds as ethyl acetoacetate, malononitrile, ethylcyanoacetate, and cyanoacetamide afforded 9–16 respectively     

Hyperconjugative interactions are the main responsible for the anomeric effect: a direct relationship between the hyperconjugative anomeric effect,global hardness and zero-point energy

The correlations between the global hardness (η), hyperconjugative anomeric effect, Pauli exchange-type repulsions, electrostatic model associated with dipole–dipole interaction and structural parameters in 2-fluorotetrahydropyran, -thiopyran, -selenopyran (1–3) and their chloro- (4–6) and bromo-analogs (7–9) were investigated by means of the conventional and range-corrected functionals and natural bond orbital (NBO) interpretation. By deletion of the HC-exo-AE and HC-endo-AE, the equatorial conformations of compounds 1–9 become more stable than their corresponding axial forms, revealing that anomeric relationships in compounds 1–9 have the hyperconjugative anomeric effect origins while the electrostatic model associated with dipole–dipole interaction does not play a determining role on the variations of the anomeric relationships in these compounds. The anomeric relationships in compounds 1–3 have no Pauli exchange-type repulsions origin, but it has a significant impact on the conformational preferences in compounds 4–6 and 7–9. A canonical molecular orbital interpretation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the global hardness (η) values. There is a direct relationship between the hyperconjugative anomeric effect, global hardness (η) and zero-point energies in compounds 1–3, 4–6 and 7–9. The harder axial conformations with the greater hyperconjugative anomeric effect and zero-point energy values are more stable than their corresponding equatorial forms.     

Neutral and cationic (pyrazolylmethyl)pyridine palladium(II) complexes: kinetics and chemoselectivity studies in hydrogenation of alkenes and alkynes

Reactions of (3,5-dimethylpyrazolylmethyl)pyridine (L1) and (3,5-diphenylpyrazolylmethyl)pyridine (L2) with either [PdCl₂(NCMe)₂] or [PdClMe(COD)] afforded the respective neutral palladium complexes, [PdCl₂(L1)] (1), [PdCl₂(L2)] (2) and [PdClMe(L1)] (3). Treatment of complex 1 with equimolar amounts of PPh₃ or PPh₃/NaBAr₄ produced the corresponding cationic complexes [Pd(L1)ClPPh₃]Cl (4) and [Pd(L1)ClPPh₃]BAr₄ (5), respectively. Complexes 1–5 formed active catalysts in hydrogenation of alkenes and alkynes. Isomerization reactions were predominant in the hydrogenation reactions of terminal alkenes, while hydrogenation of alkynes involved a two-step process via alkene intermediates prior to the formation of the respective alkenes. The lack of induction periods in the hydrogenation reactions in addition to pseudo-first-order kinetics with respect to the substrates established the homogeneous nature of the active species.     

Exploring the impacts of the vinylogous anomeric effect on the synchronous early and late transition states of the hydrogen molecule elimination reactions of cis-3,6-dihalocyclohexa-1,4-dienes

LC-ωPBE, B3LYP, and M06-2X methods with the 6–311+G** basis set on all atoms and natural bond orbital (NBO) interpretation were performed to investigate the roles and contributions of the effective factors on the potential energy surfaces of the hydrogen molecule elimination reactions of cyclohexa-1,4-diene (1) and its cis-3,6-dihalo derivatives [halogen=F (2), Cl (3), Br (4)] to hydrogen molecule and their corresponding aromatic rings. The ring puckering in compound 2 (which results from the repulsive electrostatic interactions between the natural bond orbital dipole moments of two C-F bonds) shortens the allylic hydrogen atoms’ distance, leading to the smaller barrier height in compound 2 compared to that in compound 1. The barrier heights of the hydrogen molecule elimination reactions increase from compounds 2 to 4 while their corresponding exothermic characters decrease. The variations of the advancements of transition state structures (δB _av) reveal that the hydrogen molecule elimination reactions of compounds 2–4 do not obey the Hammond-Leffler postulate. In compound 2, the ring puckering shortens the allylic hydrogen distance (d _H8-H10) while d _H8-H10 values increase going from compounds 2 to 4, leading to the increase of their corresponding hydrogen molecule elimination reactions barrier heights. Interestingly, the variations of the vinylogous hyperconjugative anomeric effects justify the directions of the rings puckering going from compounds 2 to 4. The increase of the activation exchange components [PETR _(TS)-PETR _(GS)] going from compounds 2 to 4 correlates well with their corresponding hydrogen molecule elimination process barrier heights.     

Investigation of Structural,Electronic and Biological Properties of Two Zn(II) Complexes with Pentaaza Macrocyclic Schiff-Base Ligand: A DFT Approach

Two zinc(II) complexes, [ZnL¹Br]⁺ (1), and [ZnL²]²⁺ (2), are optimized by using density functional theory at B3LYP method with mix basis sets which are LANL2DZ/6–31G(d,p) and LANL2TZ+/6–31++G(d,p) basis sets. L¹ and L² are pentadentate macrocyclic Schiff-base ligands containing piperazine moiety. The optimized structures and structural parameters are obtained by using each basis set. IR and UV–VIS spectra of complex (1) and (2) are investigated in detail. NLO properties of Zn(II) complexes are investigated and it is found that NLO properties of complex (2) is better than complex (1). Solvent effects on biological activity are investigated in gas phase, water and chloroform for studied complexes and no solvent effects are monitored for complex (1) and (2). Biological reactivity of complex (1) is higher than that of complex (2).     

Substitution of aqua ligands from <Emphasis Type="Italic">cis</Emphasis>-platinum(II) complexes bearing 2-(phenylthiomethyl)pyridine spectator ligands

Cis-Pt(II) complexes, namely [Pt{2-(phenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^Ph ), [Pt{2-(4-tert-butylphenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^{Ph( t -But)} ) and [Pt{2-(4-fluorophenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^PhF ), were synthesised and characterised. The pK _a1 and pK _a2 values of the complexes were determined titrimetrically. Substitution of the aqua ligands from these complexes by thiourea nucleophiles was studied at a pH of 2 and ionic strength of 0.1 M under pseudo-first-order conditions using stopped-flow and UV–visible spectrophotometric techniques. Substitution of the aqua ligands depends on both the nature and concentration of the incoming ligand, with low enthalpy and negative entropy of activation values. Substitution of the first and second aqua ligands occurs sequentially and fits the rate laws: k _{obs (1/2)} = k _(1/2) [Nu]. The second-order rate constant, k ₁, relates to the substitution trans to sulphur, while k ₂ is the second-order rate constant for the subsequent substitution of the aqua ligand trans to pyridine. The rate of substitution of the first aqua ligand decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^PhF ) > Pt(pyS ^Ph ), while that of the second decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^Ph ) > Pt(pyS ^PhF ), reflecting the influence of the substituents on the spectator ligands. ¹⁹⁵Pt NMR spectra of aged solutions of complexes with the thiourea nucleophile suggest a subsequent but rapid concentration-independent ring opening of the N,S-bidentate ligand to form a PtS ₄ species. The crystal structure of Pt(pyS ^PhF )Cl ₂ was elucidated by X-ray diffraction analysis.     

Amberlyst-15 catalyzed synthesis of novel thiophene–pyrazoline derivatives: spectral and crystallographic characterization and anti-inflammatory and antimicrobial evaluation

Increasing instances of antimicrobial drug resistance and Inflammation-mediated disorders requires the design and synthesis of new small-molecules with higher affinity and specificity for their potential targets to serve as antibiotics or anti-inflammatory drugs, respectively. The current study presents the synthesis of a series of chalcones, 3(a–h) by the reaction of 3-methylthiophene-2-carbaldehyde, 1 and acetophenones, 2(a–h) by Claisen–Schmidt approach. The chalcones were efficiently transformed into thienyl-pyrazolines, 5(a–h) by their reaction with thiosemicarbazide hydrochloride, 4 in the presence of Amberlyst-15 as a catalyst in acetonitrile at room temperature. Alternatively, the compounds 5(a–h) were prepared by conventional method using acetic acid (40%) medium. Structures were characterized by spectral and single crystal X-ray diffraction studies. Preliminary assessment of the anti-inflammatory properties of the compounds showed that, amongst the series, compounds 5b and 5c have excellent anti-inflammatory activities. Further, compound 5c showed excellent activity against Escherichia coli (MIC, 15 µg/mL), Bacillus subtilis (MIC, 20 µg/mL), Aspergillus niger (MIC, 20 µg/mL), and Aspergillus flavus (MIC 15 µg/mL), respectively. Compounds 5a and 5b were also found to be active against the tested microorganisms.     

Influence of the nature of the substituent in 3-(2-pyridyl)-1,2,4-triazole for complexation with Pd<Superscript>2+</Superscript>

The structure of four new palladium complexes [Pd(HL ² )Cl ₂ and Pd(L ^1–3 ) ₂ ] with 3-(2-pyridyl)-5-R-1,2,4-triazoles (R=H, CH₃, Ph respectively HL ¹ , HL ² , HL ³ ) was proposed based on IR, NMR, UV spectroscopy and MALDI mass spectrometry data analysis. It is found that the complexation of HL ² and HL ³ with Pd²⁺ ions results in a decrease of their fluorescence intensity and it is vice versa in case of HL ¹ . Furthermore, the influence of the substituent (R) in the 3-(2-pirydyl)-5-R-1,2,4-triazoles on the fluorescent and protolytic properties of HL ^1–3 was investigated.     

Conformational isomerism of the seven-membered heterocycle in a single crystal of [η<Superscript>2</Superscript>-Ph<Subscript>2</Subscript>P(O)(CH<Subscript>2</Subscript>)<Subscript>2</Subscript>C(O)NМе<Subscript>2</Subscript>]TiF<Subscript>4</Subscript> adduct

The crystal structure of TiF₄[(Ph₂P(O)CH₂CH₂C(O)NMe₂)] chelate (I) was studied by X-ray crystallography, which revealed four crystallographically independent complex molecules of similar structure (1–4). It was found that the molecules are only slightly different in the bond lengths between the coordinated atoms and the central titanium ion and considerably different in the geometry of the seven-membered TiOPCCCO chelate ring. The geometry of the chelate rings was found to be almost identical in each pair of complexes 1, 2 (A) and 3, 4 (B), and a conclusion was drawn on the presence of two conformational isomers (A and B) of the chelate complex. Quantum chemical calculations of the relative thermodynamic stability of molecules 1–4 were performed, and their geometry optimization led to one theoretical structure. The comparison of the chelate ring geometry in the theoretical structure and in conformers A and B revealed that the conformation of the theoretical chelate ring coincides with that of conformer A.     

Tuning the regioselectivity of (benzimidazolylmethyl)amine palladium(II) complexes in the methoxycarbonylation of hexenes and octenes

Reactions of N-(1H-benzoimidazol-2-ylmethyl-2-methoxy)aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl-2-bromo)aniline (L2) with p-TsOH, Pd(AOc)₂ and two equivalents of PPh₃ or PCy₃ produced the corresponding palladium complexes, [Pd(L1)(OTs)(PPh₃)] (1), [Pd(L2)(OTs)(PPh₃)] (2) and [Pd(L1)(OTs)(PCy₃)] (3), respectively, in good yields. The new palladium complexes 1–3 and the previously reported complexes [Pd(L1)ClMe] (4) and [Pd(L2)ClMe] (5) gave active catalysts in the methoxycarbonylation of terminal and internal olefins to produce branched and linear esters. The effects of complex structure, nature of phosphine derivative, acid promoter and alkene substrate on the catalytic activities and selectivity have been studied and are herein reported.