Irradiation In Methanol Research Articles

Green synthesis of chitosan-stabilized silver-colloidal nanoparticles immobilized on white-silica-gel beads and the antibacterial activities in a simulated-air-filter

This study explored the green synthesis and immobilization of colloidal silver nanoparticles (AgNPs) on a solid compatible support. Its antibacterial properties in reusable air filters are also discussed. The chitosan stabilized colloidal AgNPs (chi-AgNPs) were prepared using visible light irradiation in methanol. The UV–Vis, FTIR spectra, and TEM confirmed the chi-AgNPs formation. The immobilization technique of chi-AgNPs on the surface of white-silica-gel beads, which was previously coated chitosan (chi-SiG), was effective. The immobilized silver particles (AgNPs-[chi-SiG]) were solid, stable, dispersed, and nano-size. Both AgNPs-[chi-SiG] and chi-SiG exhibited antibacterial properties and prevented the growth of Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria in agar media. Air filter containing the AgNPs-[chi-SiG] showed high antibacterial activity against Bacillus subtilis in the air.

Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol

Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet–visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires.

Facile sonochemical synthesis of tellurium and tellurium dioxide nanoparticles: Reducing Te(IV) to Te via ultrasonic irradiation in methanol

In this study, tellurium (Te) nanostructures were synthesized via a facile sonochemical method by reducing TeCl4 to Te under ultrasonic irradiation in methanol. Moreover, by carrying out the reaction in an alkaline environment TeO2 nanoparticles were produced. According to our knowledge, it is the first time that without secondary reducing agent Te4+ are reduced to Te. Also, the effects of ultrasonic power, irradiation time, solvent, and surfactant on the morphology and particle size of Te nanostructures were investigated. The obtained products were characterized by XRD, SEM, EDS, FT-IR and DRS.

ESR spin trapping of radicals in methanol solution irradiated by heavy ion beams. Dependence on specific energy and LET

Radicals produced by the heavy ion (He, C, Ne, Si, Ar, and Fe) irradiation of methanol were spin trapped with PBN. Three kinds of radicals, PBN-CH3O, PBN-CH2OH, and PBN-H, were observed similar to those by γ-irradiation. The relative radical yields, PBN-CH3O/PBN-CH2OH and (PBN-CH3O+PBN-CH2OH)/PBN-H, varied depending on the LET value, the specific energy and mass of ions.

Synthesis, Photochemical Properties, and Cytotoxicities of 2H-Naphtho[1,2-b]pyran and Its Photodimers.

A 2H-naphtho[1,2-b]pyran, prepared by dimerization of 2-bromo-3-methyl-1,4-naphthoquinone and O-methylation, readily undergoes solid-state [2 + 2] photodimerization to give a photodimer in excellent yield and with excellent selectivity. Retro [2 + 2] cycloaddition can be achieved by irradiation of a solution of the photodimer in chloroform. Interestingly, the 2H-naphtho[1,2-b]pyran dimerizes with a skeletal rearrangement to afford 2,5-dihydro-1-benzoxepin dimers upon irradiation in methanol or via irradiation with hexamethylditin. Furthermore, treatment of the resulting dimers with triethylamine regenerates the 2H-naphtho[1,2-b]pyran monomer. Significant differences in the color, fluorescence, and cytotoxic properties of the monomer and dimers were observed.

Sonochemical synthesis and characterization of nano-sized zirconium(IV) complex: new precursor for the preparation of pure monoclinic and tetragonal zirconia nanoparticles

In this study, synthesis and characterization of two polymorphs of a new nano-sized zirconium(IV) complex, [ZrO(dmph)I2] (1), {dmph = 2,9-dimethyl-1,10-phenanthroline (neocuproine)}, have been investigated in two different solvents. The reaction between zirconyl nitrate pentahydrate and potassium iodide with dmph as a ligand under ultrasonic irradiation in methanol and mono-ethylene glycol (MEG) leads to the formation of the nano-sized Zr(IV) complex. Characterization of the Zr(IV) complex has been performed using scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and elemental analysis. The thermal stability of the compound 1 has been studied by thermal gravimetric and differential thermal analyses. Particle sizes of the compound 1 have been decreased after thermal treatments in an autoclave. Pure monoclinic (m) and tetragonal (t) zirconia (ZrO2) nanoparticles were readily synthesized from thermal decomposition of the Zr(IV) complex as a new precursor in presence of methanol and MEG as solvents, respectively. Zirconium oxide was characterized by FT-IR, XRD, and SEM to depict the phase and morphology. The results showed that, pure zirconia was produced with particle size about 59 nm and crystal system was monoclinic when methanol was used as a solvent during complexation process. On the other hand, particle sizes of zirconia with tetragonal structure were significantly reduced to about 39 nm, when MEG was used as solvent.

ChemInform Abstract: Spectacular Modification of Gambogic Acid on Microwave Irradiation in Methanol: Isolation and Structure Identification of Two Products with Potent Antitumor Activity.

AbstractBoth the reaction products (III) and (IV) can significantly inhibit the growth of various tumor cell lines in vitro.

Spectacular modification of Gambogic acid on microwave irradiation in methanol: Isolation and structure identification of two products with potent anti-tumor activity

Treatment of gambogic acid with methanol in acidic condition under microwave irradiation led to the formation of two new products bearing spectacular A ring systems which were different from reported Garcinia natural products. The chemical structures of these two compounds were elucidated by extensive NMR and MS spectroscopic analysis as well as crystallographic study. Both of the two products could significantly inhibit the growth of various tumor cell lines in vitro with IC(50) values at muM level through apoptotic pathway.

Incorporation of a Photosensitizer Core within Hyperbranched Polyether Polyols: Effect of the Branched Shell on the Core Properties

A photosensitizer core has been covalently incorporated into a hyperbranched polyether polyol structure, using a one-step protocol. Partially deprotonated 2,2‘,4,4‘-tetrahydroxybenzophenone was used as initiator in the anionic polymerization of glycidol, yielding hyperbranched polyglycerols with benzophenone core in every macromolecule formed. Molecular weights in the range of 1500 to 5800 g/mol and moderate polydispersity (1.3 < Mw/Mn < 2) were obtained. Incorporation of the functional core was unequivocally evidenced by MALDI−TOF mass spectroscopy. Further modification via acetylation of the polyglycerol hydroxyl groups afforded polymers of lowered polarity. The photochemical and photophysical behavior of the obtained benzophenone core-containing hyperbranched polyglycerols has been investigated in a variety of solvents and compared with that of the model compound 2,2‘,4,4‘-tetramethoxybenzophenone. The hyperbranched polymer periphery induced molecular weight-dependent properties in the photoactive core. Although absorption spectra of the polymers show the typical bands of a tetra(alkoxy)benzophenone unit, a dramatic hyperchromic effect of the band assigned to the 2,4-dialkoxybenzoyl chromophore was observed with increasing molecular weight. Steady-state and time-resolved fluorescence measurements evidenced an increase of both the fluorescence quantum yield and the singlet lifetime with the increase of molecular weight. On the other hand, laser flash photolysis (LFP) experiments showed that, as in the case of the reference compound, the lowest-lying triplet of the hyperbranched derivatives in methanol is mainly of the π,π* nature, while both triplets n,π* and π,π* are populated in acetonitrile, which is indicative of easy access of the solvent to the core. However, the quenching rate constant of the aromatic ketone triplet excited-state by naphthalene decreased with the polymer molecular weight, which agrees with the role of the branched shell as a barrier for external quenching. The polymers showed good photostability, i.e., degradation was insignificant upon 1 h of irradiation in methanol.

A novel photoisomerzation of 1,2‐benzothiazine 1,1‐dioxides to 1,3‐benzothiazine 1,1‐dioxides

AbstractA novel facile photoconversion of 4‐hydroxy‐1,2‐bezothiazine 1,1‐dioxides (3a‐e) into 4‐oxo‐1,3‐2H‐benzothiazine 1,1‐dioxides (4a‐e) and 4‐hydroxy‐2‐methyl‐N‐(pyridin‐2‐yl)‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide (PRX) into N‐methyl saccharin (2) upon 254 nm irradiation in methanol or acetonitrile is reported. The structures of the products have been elucidated by spectroscopic methods and single crystal X‐ray structure determination for 4a and 4d.

Mechanistical Studies on the Irradiation of Methanol in Extraterrestrial Ices

Pure ices of amorphous methanol, CH3OH(X 1A'), were irradiated at 11 K by 5 keV electrons at 100 nA for 1 hr. These energetic electrons simulate electronic energy transfer processes that occur as interstellar ices, comets, and icy solar system bodies are subjected to irradiation from MeV ions and secondary electrons produced in this process. The results were analyzed quantitatively via absorption-reflection-absorption Fourier transform infrared (FTIR) spectroscopy, with the identification of new species aided by high-level electronic structure calculations. The unimolecular decomposition of methanol was found to proceed via the formation of (1) the hydroxymethyl radical, CH2OH(X 2A''), and atomic hydrogen, H(2S1/2), (2) the methoxy radical, CH3O(X 2A'), plus atomic hydrogen, (3) formaldehyde, H2CO(X 1A1) plus molecular hydrogen, H2(X 1Σ), and (4) the formation of methane, CH4(X 1A1), together with atomic oxygen, O(1D). The accessibility of the last channel indicates that the reverse process, oxygen addition into methane to form methanol, should also be feasible. A kinetic model is presented for the decomposition of methanol into these species, as well as the formyl radical, HCO(X2A'), and carbon monoxide, CO(X 1Σ+). During the subsequent warming up of the sample, radicals previously generated within the matrix were mobilized and found to recombine to form methyl formate, CH3OCHO(X 1A'), glycolaldehyde, CH2OHCHO(X 1A'), and ethylene glycol, HOCH 2CH2OH(X 1A). Upper limits for the production of these species by the recombination of neighboring radicals produced during irradiation as well as during the warm-up procedure are presented. The generation of these molecules by irradiation of ices in the solid state and their subsequent sublimation into the gas phase can help explain their high abundances as observed toward hot molecular cores and underlines their importance in astrobiology.

Methanolysis of styrene oxide catalysed by a highly efficient zirconium-doped mesoporous silica

Highly ordered zirconium doped hexagonal mesoporous silicas with Si/Zr ratios of 40:1 and 80:1 have been used as solid acid catalysts for the methanolysis of styrene oxide in a single-mode microwave reactor. The catalysts demonstrated excellent substrate conversion, high product selectivities and were shown to remain highly active for several reaction cycles. The catalyst was regenerated by microwave irradiation in methanol. The effects of concentration of zirconium dopant and reaction time were studied. Products of the reaction were identified by a combination of GC-MS and 1H NMR as 2-methoxy-2-phenylethanol (1), phenyl-acetaldehyde (2), phenylacetaldehyde dimethyl acetal (3) and 1-(1-methoxy-2-(phenethyloxy)ethyl)benzene (4). The relative amounts of these products depended on the zirconium concentration and the reaction time. Thus, with 40:1 Si:Zr catalyst, compounds (1) (93%), (2) (5%) and (3) (2%) were produced after 5 min reaction but only (1) (93%) and (3) (7%) were observed after 10 min.

The structure, photochemical reactivity, and photophysical properties of adamantyl X-substituted aryl ethers and a comparison with the alkyl groups, methyl, tert-butyl, and allyl

The structure, photophysical properties, and photochemistry of the adamantyl aryl ethers 1 in both methanol and cyclohexane have been examined. UV absorption spectra, 13C NMR chemical shifts, X-ray structures, and Gaussian calculations (B3LYP/6-31G(d)) indicate that these ethers adopt a 90° conformer in the ground state. In contrast, fluorescence spectra, excited singlet state lifetimes, and calculations (TDDFT) indicated a 0° conformer is preferred in the first excited singlet state S1. Irradiation in either solvent results in the formation of adamantane and the corresponding phenol as the major products, both derived from radical intermediates generated by homolytic cleavage of the ether bond. The 4-cyano substituted ether 1j was the only one to form the ion-derived product, 1-methoxyadamantane (16% yield), on irradiation in methanol. Rate constants of bond cleavage for these ethers from S1 were estimated by two different methods by comparison with the unreactive anisoles 2, but the effect of substituents was too small to determine structure–reactivity correlations. The temperature dependence of the quantum yields of the fluorescence of the unsub stituted, 4-methoxy and 4-cyano derivatives of 1 and 2 were also determined. These results indicated that the activated process for 1 was mainly bond cleavage for the 4-cyano substrate whereas for 2, it was internal conversion and intersystem crossing. Key words: aryl ether photochemistry, fluorescence, excited-state rate constants, excited-state temperature effects.

Fluorinated Heterocyclic Compounds. A Photochemical Approach to a Synthesis of Polyfluoroaryl‐1,2,4‐triazoles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Fluorinated Heterocyclic Compounds. A Photochemical Approach to a Synthesis of Polyfluoroaryl-1,2,4-triazoles

The reaction of some fluorinated 1,2,4-oxadiazoles in the presence of methylamine or propylamine has been investigated. The irradiation in methanol or acetonitrile leads with acceptable yields to the corresponding fluorinated 1- methyl- or 1-propyl-1,2,4-triazole.

Meta-Substituent Effects on the Photocyclization of Aryl-substituted N-Acyl-α-dehydroalanine Derivatives

On irradiation in methanol, the title compounds having chloro, trifluoromethyl or methyl group at the meta position on the styryl benzene ring gave 6-substituted (2) and 8-substituted (3) 1-methyl-3-(methylaminocarbonyl)isoquinolines along with 1-azetines. The preferential formation of 2 to 3 was explained in terms of steric effects on the cyclization process from the excited-state (Z)-isomer. The methoxy group introduced at the same meta position exerted dramatical electronic and steric effects on the excited-state cyclization pathway giving rise to regioselectively 6-substituted 2-quinolinone and isoquinoline derivatives. The 1-naphthyl substituent in the title compounds was found to have the same effects on the cyclization pathway as the methoxyphenyl group.

A New Route to Papaverine Analogs via Photocyclization of Substituted N-Acyl-α-dehydrophenylalaninamides

(Z)-N-Phenylacetyl-a-dehydro(3,4-dimethoxyphenyl)alaninamide derivatives [(Z)-1] were prepared in satisfactory yields, starting from 3,4-dimethoxybenzaldehyde. On irradiation in methanol, regioselective photocyclization of these derivatives proceeded to give papaverine analogs in good yields. Substituents introduced into (Z)-1 were found to exert only a minor effect on the conversion of the starting isomers (1) as well as on the selectivity of the analogs which were formed along with 1-azetines.

Mechanism of Photoinduced Processes in Solutions of Iodo Iron(III) Complexes Containing Schiff Base Ligands

The mechanisms of photoinduced processes occurring in methanolic solutions of trans-[Fe(4-R-benacen)(CH3OH)I] (4-R-benacen2− : N,N′-ethylene-bis-(4-R-benzoylacetoneiminato) tetradentate open-chain Schiff bases with R = H, Cl, Br, CH3, OCH3, or NO2) were investigated by electronic absorption spectroscopy and EPR spin trapping. The complexes are redox-stable in the dark both in the solid state and in methanolic solutions. Ultraviolet and/or visible irradiation in methanol induces photoreduction of Fe(III) to Fe(II). No formation of I˙ or \(\) was observed. ˙CH2OH radicals and/or solvated electrons were identified in irradiated systems using nitrosodurene or 5,5-dimethyl-1-pyrroline-N-oxide as spin traps. The final product of the photooxidation coupled with the photoreduction of Fe(III) is formaldehyde, the molar ratio of Fe(II) and CH2O being close to 2:1. The efficiency of the photoredox process is strongly wavelength dependent and influenced by the peripheral groups R of the tetradentate ligands. It is suggested that the primary photoredox step starts from thermally nonequilibrated ligand-to-metal charge transfer excited states.

Synthesis and photo-oxidative degradation of 2,6-bis-[ω-trimethylsiloxypolydimethylsiloxy-2′-dimethylsilylethyl]acetophenone

Dihydridocarbonyltris(triphenylphosphine)ruthenium (Ru) catalyzes the copolymerization of α,ω-divinylsiloxanes with aromatic ketones such as acetophenone to give polymers which have regularly alternating 2,6-diethylene-acetophenone and disiloxane units in the backbone. These copolymers absorb light in the UV λ max ∼280 nm, and are photochemically active. Monomeric model systems 2-(2′-trimethylsilylethyl)acetophenone ( III), and 2-(3′,3′,5′,5′,5′-pentamethyl-3′,5′-disila-4′-oxaheptanyl)acetophenone ( IV), as well as, 2,6-bis[ω-trimethylsiloxypolydimethylsiloxy-2′-dimethylsilylethyl]acetophenone ( II) were prepared and their photochemistry in the presence and absence of oxygen studied. Photolysis of alt-copoly(2,6-diethylene-acetophenone/disiloxane) in the absence of oxygen results in recovered polymer whose molecular weight has not changed. On the other hand, photolysis in the presence of oxygen results in significant polymer degradation. Likewise, III was stable to irradiation in methanol- d 4 solution in the absence of oxygen. Deuterium was specifically incorporated into the benzylic methylene groups of recovered III. The photolysis of III in the presence of oxygen yields hexamethyldisiloxane and 1,2-diacetylbenzene. Mechanisms that accounts for these results are proposed.

Photoreactions of trans-1-o-Hydroxyphenyl-2-phenylcyclopropane.

The photochemistry of trans-1-o-hydroxyphenyl-2-phenylcyclopropane, trans-1, was studied under a variety of experimental conditions. Direct irradiation through quartz in cyclohexane gave rise mainly to ring-expanded products, 2-phenyl-3,4-dihydro-2H-benzopyran, 2, 2-benzyl-2,3-dihydrobenzofuran, 3, and 1-o-hydroxyphenylindan, 4. The major products, 2 and 3, are rationalized by intramolecular proton transfer. However, a significant fraction of 3 is formed via ring-opening to cinnamylphenol, 5. An additional product, o-(alpha-cyclohexylmethyl)phenol, 7, suggests fragmentation of trans-1 and (formal) insertion of o-hydroxyphenylcarbene into cyclohexane. Direct irradiation in methanol produced methanol adducts 8 and 9 instead of 2, 3, 4, or 7. Finally, acetone-sensitized irradiation of trans-1 resulted in geometric isomerization to cis-1; this result can be rationalized via a biradical intermediate.