Search

A new series of ether-linked, per-fluorinated organic polymers bearing azo- (-N = N-) and azomethane (-C = N-) organic linkers was reported. The synthetic methodology relied on applying the nucleophilic aromatic substitution reaction (NAS) to fluorinated linkers (e.g. decafluorobiphenyl and hexaflourobenzene) and diols of azo- and azomethane linkers. The successful formation of the new structures revealing ether-linkage substitution of selected fluorine sites was confirmed by 1H-, 13C-, 19F-NMR and FTIR. All polymers were thermally stable in the range of 350–500 °C due to the variation of fluorine and nitrogen contents. The extended conjugation of the polymers was confirmed by the changes in the UV-Vis spectra of the organic linkers and their corresponding polymers. A notable hypsochromic shift was observed in all cases, which was more pronounced with azo-based fluorinated chains due to the H-bonding on the nitrogen sites, chain conformations and planarity. The optical band gap (Eg) of the polymers was determined from the UV-Vis. The Eg values of azo-based fluorinated polymers were higher by 1eV compared to their corresponding linkers. The 19F-NMR analysis confirmed two types of NAS on both the ortho- and para- positions of the fluorinated linkers. These connections created the possibility of developing cross-linked frameworks beside the open-chain confirmation with tailored hydrophobic nature. The cross-linking formation was characterized by porosity measurements, including surface area (SA), pore size and pore volume. The highest measured values were recorded for the azo-based polymer (DAB-Z-1h), which reached 438 m2/g and a pore volume of 0.35 cm3/g. A surface area of 105 m2/g was the lowest for the open-chain azomethane-based polymer (DAB-A-1O) with a pore volume of 0.0872 cm3/g. The beneficial formation of porous structures with varied hydrophobic nature was investigated as adsorbents for separating water/benzene, water/phenol and the selective binding of methane/carbon dioxide gases from the air. The most hydrophobic polymers that contain the decafluorbiphenyl linker were suitable for benzene separation, and the superior methane uptake values were 6.14 and 3.46 mg/g, for DAB-Z-1O and DAB-A-1O, respectively. On the other hand, DAB-Z-1h, with the highest surface area (438 m2/g) and rich with nitrogen sites, has the highest CO2 uptake at 298 K (17.25 mg/g).

In this report, an open-chain ether-linked polymer (PE-AF) has been prepared via one-step co-condensation polymerization of 1,4-dibromo-2,5-difluorobenzene with bisphenol AF. The new polymer has sh...

Four new symmetrical Schiff bases derived from 2,2’-diamino-4,4’-dimethyl-1,1’-biphenyl-salicylaldehyde have been synthesized and characterized by elemental analysis and different spectroscopic techniques. The reaction of 2,2’-diamino-4,4’-dimethyl-1,1’-biphenyl with two equivalents of 5-tert-butyl-, 3,5-dinitro-, 3,5-dibromo- and 3-tert-butyl-salicylaldehyde yielded 2,2’-bis(5-tert-butyl-salicylideneamino)-4,4’-dimethyl-1,1’-biphenyl (A1) as well as the 3,5-dinitro- (A2), 3,5-dibromo- (A3) and 3-tert-butyl- (A4) substituted derivatives. The tetradentate ligands were then reacted with copper-, manganese- and zinc-acetate producing the tetra-coordinate metal complexes which were characterized by FTIR, UV-Visible spectroscopy, magnetic susceptibility and elemental analysis. Zinc complexes were characterized by 1H-NMR spectroscopy. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level of theory were carried out to fully optimize and examine the molecular geometries of complexes. Subsequently, IR vibrational and UV-Vis absorption spectra were computed and correlated with the observed values and the results are in good agreement with the experimental data. The anticancerous and antiproliferative activity of the A3 ligand and its metal complexes were determined.

The reaction of M(OAc)2 with 2,2′-bis(2-hydroxybenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl (H2L1) allows the synthesis of 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl complexes of Cu(II) (CuL1), Co(II) (CoL1) and Ni(II) (NiL1) that were characterized by elemental analysis, FTIR spectroscopy and for CuL1 also by X-ray crystallography verifying a tetradentate binding mode of L1 via an (ONNO) motif of the two phenolic oxygen atoms and two azomethine nitrogen atoms. Recrystallization from a solvent mixture of dichloromethane and methanol promotes the formation of methanol adducts. Different binding modes of the methanol–complex were investigated using density functional theory calculations and binding energies, and thermodynamic data of the interaction are reported. The results show that the favored interaction occurs when the methanol molecule acts as a Lewis acid weakly binding via an O–H···O hydrogen bridge to a phenoxide moiety leading to an elongation of the respective M–O bond.

New photophysical and antioxidant materials of trimesic trihydrazide derivatives were synthesized by one-pot stage of trimesic trihydrazide and different aromatic aldehydes. All compounds were characterized by spectroscopic techniques (NMR, MS, and IR) and elemental analysis. The absorption and emission spectral characteristics of hydrazone derivatives were investigated. The absorption maxima showed red shift relative to the starting compound. While the emission maxima showed clear dependent on the type of substituents. The electron donating and electron withdrawing showed red and blue shifts relative to the starting compound, respectively. The compounds’ effectiveness as antioxidant was estimated by DPPH radical scavenging and ABTS radical cation assays in vitro which indicated that the derivatives could be used as potential antioxidants. In addition, compounds 3g, and 3i showed strong antioxidant activities according to the DPPH assay and compounds 3c and 3m exhibited good antioxidant activities in ABTS assay. Antimicrobial activity of the derivatives was estimated using a micro-broth dilution method. Furthermore, molecular geometries of all prepared derivatives were fully optimized using density functional theory (DFT) calculations at the 6-31G(d)/B3LYP level of theory., Trimesic acid, Hydrazones, Antioxidant, Spectrophotometric, Fluorescence, DFT.

Fe(III) complexes, [Fe(CH3CN)6][X]3 and [Fe(CH3CH2CN)6][X]3 (where X: counter anion = B{C6H3(m-CF3)2}4)− and B(C6F5)4−) have been synthesized by the reaction of FeCl3 with Ag[B(X)4]. Full characterization for the complexes has been done in solution and in the solid state. The complexes are obtained in good yields and are moderately sensitive to air. All complexes have been used as catalysts for aniline oxidation with yields up to 62%, in which azobenzene is the only product. Furthermore, they exhibit good antimicrobial properties. The Fe(III) complexes molecular geometries have been studied using DFT calculations at the B3LYP/6-31G(d) and B3LYP/6-31+G(d, p) levels of theory and obtained results are in agreement with the experimental data.

A series of new imine-linked polymers reveal variations of aliphatic and aromatic linkers were synthesized via Schiff base co-condensation polymerization and fully characterized. The polymers are classified as 1,4- and 1,6-based polymers according to their preparation methodology, which depicted by the polymerization of thiophene-based aryl aldehydes with1,4-butanediamine and 1,6-hexanediamine, respectively. The interpretation of their thermal stability from the thermal gravimetric analysis and the first derivative (TGA-DTG) curves have indicated that the variation in the contents of the aryl-aldehydes and the length of the linker are significantly affect the thermal stability behavior. For example, the polymer prepared via the connection of ter-thiophene-aldehyde with 1,4-butanediamine (1,4-TIP) has shown higher thermal stability, higher char residue content, higher limited oxygen index (LOI = 32) than the polymer prepared by bi-thiophene-phenyl-aldehyde (1,4-F2IP) in the same manner. Furthermore, 1,4-TIP has shown the highest LOI value over all polymers and thus, can be considered as a flame-retardant polymer. However, an inverse relation has been observed upon the inclusion of 1,6-hexanediamine with the same aryl-aldehydes. Further insight into the TGA curves was performed by applying well-known fitting models: Coats-Redfren (CR), Arrhenius, Briodo, and Horowitz-Metzeger for the determination and comparison of the activation energy (Ea) values upon degradation process. The CR-method was further used for the determination of the kinetic triplet parameters (Ea), reaction order (n) and pre-exponential factor (A) and thermodynamic parameters include entropy, the heat of enthalpy, and Gibbs free energy of the polymers. All these methods support the fact that the degradation mechanism follows first-order kinetics, thermodynamically favored and the higher thermal stability polymer requires higher (Ea) for thermal degradation.

The synthesis, porosity and the capability for carbon dioxide gas-capture of functionalized thiophene- pyridine microporous imine-linked polymer synthesized via the Schiff base condensation reaction between (1,3,5-triformyl thienyl benzene) and 2,6-diaminopyridine is described. The structural formation of the polymer was successfully confirmed via 13C NMR (CP-MAS) and IR spectroscopy, and elemental analysis. The polymer has the good thermal stability up to 380°C, a non-defined aggregated particles morphology and amorphous nature. From the argon sorption isotherm at 87 K, the polymer revealed a moderate Brunauer–Emmett–Teller surface area (372 m2/g) and micro-size pores (~5 A). The CO2 uptake was studied at 273 and 298 K to evaluate the polymer tendency for capturing CO2 from the surrounding atmosphere. At 298 K, the polymer has shown a reversible adsorption-desorption isotherm with significant uptake (11.4 wt %) at 1.0 atm. The binding energy of CO2 at zero gas coverage is 24 kJ/mol and decreased upon loading.

Batch kinetic experiments were performed for the sorption of nickel ions onto nanobentonite. The kinetic data were adjusted with pseudo-first-order and pseudo-second-order kinetics by linear and nonlinear regressions in addition to some fixed suggested fractional orders $$1/2 \le n \le 5/2$$ . The removal process was found to be well explained by nonlinear pseudo-second-order kinetic expression with 0.5222 mg $$\hbox {g}^{-1}$$ standard deviation, whereas linear regression is improper method for obtaining the kinetic parameters of the studied models specially at lower order values. The kinetic rate constants were increased with the value of the prefixed reaction pseudo-order giving optimal pseudo-average order equal to 3.522 with standard deviation 0.0815 mg $$\text {g}^{-1}$$ . This optimal value is estimated at infinite time which is physically become closer to the reality of the studied system. Nevertheless, the theoretical removal capacity (22.95 mg $$\text {g}^{-1})$$ calculated by optimal order value is greater than the experimental one (19.15 mg $$\text {g}^{-1})$$ . This behavior can be attributed to the rapidity of the process to reach the equilibrium state.

[Ln (phen)2(NO3)3] complexes were synthesized by interaction of lanthanide nitrate {Ln (NO3)3.xH2O where Ln = Tb, Eu, Sm, Dy, and La} with 1,10-phenanthroline {phen} in ethylacetate. The complexes were characterized by several analytical and spectroscopic techniques. Density functional theory (DFT) calculations were carried out to optimize the geometries of all prepared complexes at the B3LYP/6-31G(d) level of theory. Vibrational frequencies of the complexes theoretically calculated were in good agreement with experimentally determined values. Most of the complexes exhibited high to moderate antibacterial and antifungal activities in vitro against seven different clinical isolates. The complexes were tested for their antioxidant activity toward 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical. Dy(III) complex showed the highest activity. Thermal degradation of complexes at different heating rates was investigated by thermogravimetric analysis (TGA). The complexes had high thermal stability. The activation energies (E a ) of the degradation were calculated by Kissinger and Flynn-Wall-Ozawa methods.

Water soluble mono-cationic copper(II) complex of the general formula [Cu(NO2-phen)2Br]Br, (NO2-phen=5-nitro-1.10-phenantholine) was prepared in good yield under ultrasonic irradiation. The desired complex was isolated as a bromide salt and identified by MS, EA, UV-Vis., TG/DTA, FT-IR and XRD. The single-crystal X-ray diffraction and Hirschfield analysis revealed a square pyramidal distorted geometry around the Cu(II) center. The geometry of the [Cu(NO2-phen)2Br]+ complex was fully optimized with ab-initio methods and (DFT/B3LYP) density functional theory, then structural parameters were compared to the XRD data. The solvatochromism of [Cu(NO2-phen)2Br]Br complex was investigated in several polar solvents. Absorption and viscosity titration studies concluded that the [Cu(NO2-phen)2Br]Br complex is a very good CT-DNA binder.

New lanthanide complexes [Ln(LH2)2(NO3)2]NO3 have been synthesized by reaction of Ln(NO3)3·xH2O {Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er} with N-(2-carboxyphenyl)salicylideneimine Schiff base ligand (LH2). A ten-coordinated lanthanide structure has been proposed based on elemental analysis, spectroscopic analysis (UV–Visible, FT-IR, 1H and 13C NMR), molar conductance and thermal analysis. The molecular geometry of the cationic complex [Sm(LH2)(NO3)2]+ has been examined using DFT calculations at the B3LYP/6-31 G(d) level of theory and the obtained results are in good agreement with the experimental data. The absorption, excitation and emission spectral characteristic of LH2 and Ln-LH2 complexes in DMF and methanol have been investigated. The Eu-LH2, Sm-LH2 and Tb-LH2 complexes display characteristic lanthanide-centered luminescence. The antioxidant activity of LH2 ligand and its Ln(III) complexes has been estimated in terms of the DPPH free radical scavenging activity (DPPH-RSA). The photoconductivity of the LH2 ligand and Ln-LH2 (Pr, Gd, Nd, Sm, and Tb) complexes has also been studied. The results show that Pr-LH2, Nd-LH2 and Gd-LH2 complexes exhibit a remarkable photoconductivity.

A pyridine-diacylhydrazone Schiff base ligand, L = 2,6-bis[(3-methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X-ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO3)2]NO3.xH2O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra-red (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO3)2]+ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT-IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.

A new series of extended–conjugated and thermally stable thiophene-containing imine-linked polymers were synthesized via a Schiff-base condensation reaction between aryl aldehydes and 2,6-diaminopyridine building blocks. The backbones of the polymers were functionalized with phenyl, fluorosubstituted phenyl, thienyl, and pyridyl aromatic rings. The successful synthesis was confirmed with spectrochemical characterization techniques, including IR, 1H-NMR, 13C-NMR, and elemental analyses. The electronic properties of the polymers were investigated with ultraviolet–visible (UV–vis) absorption spectroscopy; the properties were collected experimentally and calculated with density functional theory (DFT) in the gas phase. The maximum absorption calculated from DFT was higher than the experimental values by about 60 nm; this was attributed to the absence of the solvent effect in the DFT case. The frontier molecular orbital ((HOMO) highest occupied molecular orbital and (LUMO) lowest unoccupied molecular orbital), optical band gap (Eg), and total energy (ET) values of the optimized structures were calculated. Apparently, there was a significant relation between the number of thiophene rings and the resulting Eg and ET values. As the number of thiophene rings in the polymer chain increased, Eg and ET decreased, and the thermal stability of the polymers increased. Eg and the absorption band edges were determined experimentally from the UV–vis and transmittance spectra, respectively. Poly(terthienyl–azomethine–pyridine–azomethine), with the highest thiophene content, had the lowest experimental and calculated Eg values (2.10 and 2.63 eV, respectively). In contrast, upon fluorination, poly[(2,5-dithienyl–1,4-difluorobenzene)–azomethine–pyridine–azomethine] exhibited the highest Eg (2.81 eV) and absorption band edges (2.94 eV), whereas the thermal stability decreased to 250 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44331.

In this study, geometrical optimizations, infrared spectroscopic analysis and relative stabilities of 1-methylcyclobutene and methylenecyclobutane tautomers were investigated by utilizing high-level ab initio and DFT calculations. The thermodynamic data showed that 1-methylcyclobutene is the more stable isomer with enthalpy [Formula: see text][Formula: see text]kcal/mol and Gibbs energy [Formula: see text][Formula: see text]kcal/mol lower than that for methylenecyclobutane at the M06/aug-cc-PVTZ level of theory. These results are in good agreement with the available experimental data. Additionally, the geometrical parameters and vibrational frequencies agree well with the recorded results in literatures.

Fe(III) complexes of general formulae [FeIII(CH3CN)6][B(Ph)4]3 (1) and [FeIII(C2H5CN)6][B(Ph)4]3 (2) were synthesized by a direct reaction of FeCl3 and Ag(B(Ph)4) in acetonitrile and propionitrile, respectively. The complexes were characterized in the solid state and in solution. The complexes were used as catalysts for the oxidation of aniline and its derivatives. Complex 1 has better activity than complex 2, with product yield reaching 60%. The Fe(III) complexes exhibit good antibacterial and antifungal activities. The molecular geometries of the prepared iron(III) complexes were examined using density functional theory calculations at the B3LYP/6-31G(d) level of theory and the results obtained are in good agreement with experimental data.