Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)... more Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)-tetrazole-5-stannylenes (1R), and 1,3-di(R)-tetrazole-5-stannylenes (2R), using B3LYP/6-311++G** level of theory. Nucleophilicity, multiplicity, and stability of 1R and 2R are calculated; with R = H, methyl, ethyl, i-propyl, t-butyl, Ph, OH, methoxy, NO2, CN and CF3. Asymmetric 2H appears more nucleophilic (N 4) than its corresponding symmetric 1H isomer (N 3), mostly due to the formers higher separation of charge. The N is more sensitive to electronic effects in 1R stannylenes than those in the 2R series. Electron donating R groups increase N with Hammett ρ constants of -3.3 and -2.7 for 1R and 2R, respectively. Stannylene 2H is slightly more aromatic (NICS (1) = -10.31) than 1H (NICS (1) = -10.25). Every 1R is more stable than its corresponding 2R isomer. Every 2R is generally more nucleophilic and aromatic than its corresponding 1R. In addition the former is less electrophilic with a...
A novel magnetic chitosan hydrogel film, crosslinked with glyoxal (Fe 3 O 4 NPs/CS/glyoxal), has ... more A novel magnetic chitosan hydrogel film, crosslinked with glyoxal (Fe 3 O 4 NPs/CS/glyoxal), has been synthesized and used as an easily reusable adsorbent for 80-90 % removal of toxic Cr(VI) from water. A pseudo-second-order kinetic (with correlation coefficient R 2 > 0.99) is observed at room temperature. Characterization of the absorbent is carried out by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption isotherm is well fitted in the Langmuir equation at different temperatures [R 2 > 0.99, and 0< (Langmuir separation factor, R L ) <1]. So, our adsorbent, with the novelty of using glyoxal, and the ease of separation may be considered in Cr(VI) wastewater treatment technology.
The topology of nitrogen atoms is found to play an important role in the racemization of non-plan... more The topology of nitrogen atoms is found to play an important role in the racemization of non-planar diazacycloheptatetraenes through their corresponding singlet diazacycloheptatrienylidene transition states, at B3LYP/6-311++G**, MP2/6-31G*, MP4(SDTQ)/6-31G*//B3LYP/6-311++G**, CCSD(T)/6-31G*// B3LYP/6-311++G**, and QCISD(T)/6-31G*//B3LYP/6-311++G** levels of theory. Two types of singlet carbenes are encountered: r 2 and p 2 . The r 2 (-1 A) carbenes are aromatic and include 2,3-; 2,4-; 2,5-, and 3,4diazacycloheptatrienylidenes, while p 2 (-1 A 0 ) carbenes turn out antiaromatic and include 1,6-; 1,2-; 1,3-; 1,4-; and 1,5-diazacycloheptatrienylidenes. All singlet carbenes showed a negative force constant and except for the 1,6-isomer the rest appear of higher energy than their corresponding triplet states. Nevertheless, all allenes emerged more stable than their corresponding singlet and triplet carbenes. Due to higher energy barriers, racemization is unlikely for allenic structures including 2,3-; 2,4-; 2,5-; and 3,4-diazacyclohepta-1,2,4,6-tetraenes. In contrast, carbene-like reactivity is expected from ketenimine and carbodiimide (1,2-; 1,3-; 1,4-; 1,5-; 1,6-diazacyclohepta-1,2,4,6-tetraenes) which go through N-heterocyclic transition states that are mostly of rather lower energy.
Physica E: Low-dimensional Systems and Nanostructures, 2009
Silver nanoparticles (Ag NPs) were synthesized by g-irradiation of silver ions in aqueous solutio... more Silver nanoparticles (Ag NPs) were synthesized by g-irradiation of silver ions in aqueous solutions containing polyvinyl pyrrolidone (PVP). Increasing of g-irradiation doses from 1 to 5 kGy enhanced the concentration of Ag NPs, indicated by UV-vis analysis. The XRD and the TEM measurements showed the production of face-centered cubic (fcc) Ag NPs with a mean size of about 16 nm. The produced nanoparticles were effectively stabilized by PVP through interactions, confirmed by the FT-IR. The relatively higher antibacterial activities of Ag NPs, synthesized through g-irradiation method, against E. coli indicate their potential for practical applications as biocidal materials.
Materials Science in Semiconductor Processing, 2014
ABSTRACT Novel magnetic nanocomposites are synthesized by loading reduced graphene oxide (r-GO) w... more ABSTRACT Novel magnetic nanocomposites are synthesized by loading reduced graphene oxide (r-GO) with three brands of nanoparticles consisting of titanium dioxide (TiO2), gamma-iron(III) oxide (γ-Fe2O3), and silver (Ag) with varying amounts. The resulting Ag/TiO2/γ-Fe2O3@r-GO demonstrates synergistically enhanced visible light photocatalytic activity, on degradation of wastewater׳s toxic crystal violet (CV). Specifically, it exhibits higher photoactivity than those of neat graphene oxide (GO), TiO2@GO, γ-Fe2O3@GO, and TiO2/γ-Fe2O3@GO, possibly because of effective separation of photogenerated carriers via strongly coupled Ag/γ-Fe2O3@r-GO cocatalyst and the enrichment of organic molecules on the graphene nanosheets. A higher photocatalytic efficiency is observed when 11.5 wt% Ag nanoparticles are incorporated in TiO2/γ-Fe2O3@GO. After 3 successive cycles, the latter nanocomposite maintains 97% removal efficiency with excellent stability and easy recovery. Considering its facile preparation and high photocatalytic activity, it is hoped that this photocatalyst will find its application in various fields such as air purification and wastewater treatment. The structure and properties of Ag/TiO2/γ-Fe2O3@r-GO are characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), ultraviolet–visible spectrometry (UV–vis) and Raman spectroscopy techniques.
In regard to the worldwide interest in synthesis and application of stable carbenes, ab initio an... more In regard to the worldwide interest in synthesis and application of stable carbenes, ab initio and DFT calculations (CCSD(T)/6‐311G*//QCISD/6‐31G* and B3LYP/AUG‐cc‐pVTZ//B3LYP/6‐31 + G* levels) are employed to reach at a series of symmetrically substituted diheteroatom carbenes. In this way the multiplicity, stability, and reactivity of diethylcarbene and its saturated and unsaturated cyclic congeners are compared and contrasted to the corresponding disilyl‐, diamino‐, diphosphino‐, dioxy‐, and dithiocarbenes. The investigations reveal the enlargement of the singlet–triplet energy gaps (ΔES‐T) in the order of (amino ≈ oxy) > thio > phosphino > alkyl > silyl. The observed trend is thoroughly analyzed applying appropriate isodesmic reactions which differentiate the substituent effects on each of the singlet and triplet states of all the carbenes. In contrast to previous reports, it is found that π‐donor/σ‐acceptor amino substituents stabilize not only the singlet but also ...
Ab initio studies show the possibility of involvement of cyclic, planar, singlet and/or triplet 2... more Ab initio studies show the possibility of involvement of cyclic, planar, singlet and/or triplet 2-X-2,4,6,8-cyclononatetraenylidenes, carbenic transition states (1 Ã XÿS and/or 1 Ã XÿT ), in the conversion of cyclic conjugated non-planar allenes, 1-X-1,2,4,6,8-cyclonona-pentaenes (1 X ), to their corresponding mirror images, 1 0 X (where XZH, F, Cl and Br).
Coprecipitation of FeCl 2 and FeCl 3 produced magnetic iron nanoparticles (Fe 3 O 4 NPs). The lat... more Coprecipitation of FeCl 2 and FeCl 3 produced magnetic iron nanoparticles (Fe 3 O 4 NPs). The latter was dispersed in an acetic acid solution of chitosan (CS), and then cross-linked with glyoxal, followed by addition of polyvinyl alcohol (PVA). The resulting gel was neutralized with NaOH giving our novel Fe 3 O 4 NPs/CS/glyoxal/PVA hydrogel film. This film was used as an efficient and reusable adsorbent for the removal of toxic Cr(VI) from water, at a rather wide range of pH. The absorbent film was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and energy dispersive X-ray. Langmuir isotherm model suggested maximum Cr(VI) adsorption occurring at room temperature. Kinetic studies suggested a pseudo-second-order model for the adsorption. Our Fe 3 O 4 NPs/CS/glyoxal/PVA hydrogel is hoped to serve as a promising Cr(VI) adsorbent in wastewater treatment technology.
F 3 CA € GeAGe"GeAH, with two unpaired electrons, is the only triplet (t) ground state germylene ... more F 3 CA € GeAGe"GeAH, with two unpaired electrons, is the only triplet (t) ground state germylene found among 30 divalent species, with XHGe 3 formula, at six reasonably high ab initio and DFT levels (X = H, NH 2 , SiH 3 , and CF 3). Its corresponding singlet (s) appears at a higher energy while showing a negative force constant. The crossing angle (U) between the above s and t states is 90°. Replacement of CF 3 with H and NH 2 increases U to 120°and 160°, respectively. No crossing of the s and t states occurs for H 3 SiAGeAGe"GeAH, whose s state is its global minimum. Having X directly attached to the divalent germylene in XAGeAGe"GeAH, increases the X effects on DE s-t,X compared to the isomeric species: 3-X-1,2,3-trigermapropargylene, 3-X-1,2,3-trigermavinylidene and 2-X-1,2,3-trigermacyclopropenylidene, respectively. Nonetheless, the latter cyclic divalent species appear relatively more stable with the highest LUMO-HOMO energy gaps, while their NICS calculations show their aromatic character change as a function of X (SiH 3 > H > CF 3 > NH 2). Finally, the global minimum among the 30 isomeric XHGe 3 is found to be SiH 3 substituted singlet trigermacyclopropenylidene.
To optimize the arc fabrication of aluminum nanoparticles (Al Nps), six diverse media were probed... more To optimize the arc fabrication of aluminum nanoparticles (Al Nps), six diverse media were probed including ethylene glycol (EG), distilled water, liquid nitrogen, gaseous nitrogen, sunflower oil, and tap water (all free of any surfactant or stabilizer). These were investigated at three different currents: 50, 100 and 150 A/cm 2 . EG at 50 A/cm 2 provides the best recipe for the arc fabrication, giving the relatively purest, most dispersed and the smallest size Al Nps (26.6 nm), with the highest yield (91.5 %). Regardless of the medium used, the SEM analyses show that the size increases of Al Nps are directly proportional to the current density employed. The observed sizes for Al Nps in EG (at three different currents/A cm -2 ) are 26.6 nm (50), 64.9 nm (100), and 72.5 nm (150). Also, regardless of the current employed, the SEM analyses show different Al Nps size distributions, depending on the medium nature. The XRD extracted average sizes of the arc fabricated Al Nps show reasonable linear correlations with their corresponding elemental weight% or atomic%, acquired through energy-dispersive X-ray spectroscopy (EDX). High quantities of separable industrially significant nanoAl oxides (γ -Al 2 O 3 , Al(OH) 3 ) are fabricated along with Al Nps in tap water. In EG medium, TGA revealed only ∼7% weight loss, indicating thermal stability of the fabricated Al Nps.
A simple and effective one-pot coprecipitation of iron (II) and (III) chlorides, in the presence ... more A simple and effective one-pot coprecipitation of iron (II) and (III) chlorides, in the presence of graphene o xide (GO), resulted in the fabrication of the magnetite-GO hybrid-nanoparticles (GO@NanoFe3O4). Loading of the latter over polystyrene (PS) through in situ emulsion polymerization afforded a novel composite (GO@NanoFe3O4/PS). The TGA analysis demonstrated the anticipated thermal stabilities for NanoFe3O4@GO/PS. Furthermore, improvement of magnetic and mechanical properties of polystyrene by its loading with magnetite-GO hybrid was established through VSM and DMTA analyses.
Benzyltrimethylammonium fluorochromate (VI), BTMAFC, is synthesized by reacting benzyltrimethylam... more Benzyltrimethylammonium fluorochromate (VI), BTMAFC, is synthesized by reacting benzyltrimethylammonium bromide with an aqueous solution of CrO3 and HF. This new reagent, (C6H5CH2)(CH3)3N[CrO3F ], is used for almost quantitative conversion of oximes into the parent ketones or ...
A novel, magnetically recoverable nanocatalyst is fabricated through simple immobilization of cop... more A novel, magnetically recoverable nanocatalyst is fabricated through simple immobilization of copper(II) acetylacetonate on the surface of amine-terminated silica-coated Fe 3 O 4 nanoparticles: Cu(acac) 2 /NH 2-T/SiO 2 @Fe 3 O 4 NPs. Unambiguous bonding of Cu to the terminal amine is indicated by Xray photoelectron spectroscopy (XPS). Further characterizations are carried out by different techniques. Selectivity of this catalyst is demonstrated through one-pot synthesis of fourteen α-aminoacyl amides using Ugi four-component reaction of cyclohexyl isocyanide, acetic acid, amines and various aldehydes. Interestingly, all aromatic aldehydes react with short reaction times and high yields, but heteroaromatic aldehydes do not yield any product. Catalyst efficiency remains unaltered through three consecutive experiments.
INTRODUCTION Arc discharge is believed to play a role in originating life through experiments per... more INTRODUCTION Arc discharge is believed to play a role in originating life through experiments performed under simulated conditions after Earth first accreted from the primordial solar nebula [1]. These experiments used a highly reduced mixture of gases (methane, ammonia and ...
Singlet-triplet energy splittings for 24 GeCNX germylenic reactive intermediates are compared and... more Singlet-triplet energy splittings for 24 GeCNX germylenic reactive intermediates are compared and contrasted at 10 levels of theory: B1LYP/6-311++G**, B3LYP/6-311++G**, MP3/6-311+G*, MP3/LANL2DZ, MP2/6-311++G**, MP4(SDTQ)/6-311++G**, QCISD(T)/6-311++G**, CCSD(T)/6-311++G**, G1 and G2 (where X = H, F, Cl, and Br). Singlet (s) and/or triplet (t) GeCNX, are confined to the following three structures: 3-X-2-aza-1-germylacyclopropenylidene (1 s-X , 1 t-X), [(X-imino)methylene]germylene (2 s-X , 2 t-X), or X-cyanogermylene (3 s-X , 3 t-X). For every of these three structures the order of singlet-triplet energy separations (DE s-t,X), appears as a function of electro-negativity (F > Cl > Br > H). Fascinatingly, two triplet structures 2 t-H and 3 t-H appear more stable than their corresponding singlet states. Good linear correlations are found between the LUMO-HOMO energy gaps of the singlet germylenes, and their corresponding singlet-triplet energy separations, calculated at B3LYP/6-311++G**. Relative energies of the divalent 3 s-X and/or 3 t-X structures are plotted as a function of the divalent bond angle \X-Ge-CN, where the singlet and triplet germylenes GeCNH cross at 134°. Little germanium d orbital valence participation is found in the cyclic triplet structures 1 t-X. The global minimum, among six GeCNH species, appears to be the singlet cyclic 1 s-H. However, the global minima among the other eighteen GeCNX (X6 ¼H) species appear to be the singlet acyclic 3 s-X. Among all the calculation methods employed, B3LYP appears as the method of choice.
Si36H18, Si40H20, Si44H22, and Si48H24, respectively, at B3LYP levels (n, number of fused benzeno... more Si36H18, Si40H20, Si44H22, and Si48H24, respectively, at B3LYP levels (n, number of fused benzenoid rings). These are a brand of silicon nanorings that bear a resemblance to the shortest zig-zag silicon nanotubes (SiNTs), henceforth referred to as SiNRs. The NBO results ...
The main goal of this work is to find a more stable seven-membered ring 1H-phosphepine connected ... more The main goal of this work is to find a more stable seven-membered ring 1H-phosphepine connected to its bicyclic benzene phosphine valence tautomer after passing through a nonplanar transition state. This challenge is met by probing the impacts of substituents (X = H, F, Cl, Br, CN, ...
Zinc oxide nanoparticles (ZnO NPs, ca. 22 nm) were used as an effective catalyst in the solvent-f... more Zinc oxide nanoparticles (ZnO NPs, ca. 22 nm) were used as an effective catalyst in the solvent-free, three-component couplings of aldehydes, aromatic amines and dialkyl phosphites at room temperature to produce various a-amino phosphonates. Compared to known methods, satisfactory results were obtained with high yields through a simple experimental procedure. The catalyst was recycled and reused five times with minor decrease in its catalytic activity.
Following our quest for new divalents, we report the synthesis of P-heterocyclic silylenes (PHSis... more Following our quest for new divalents, we report the synthesis of P-heterocyclic silylenes (PHSis) by adding from one to four phosphorous atoms to saturated cyclopentasilylene (1) and unsaturated cyclopentasilylene-3-ene (1') resulting in respective PHSis (2—10 and 2'—10', respectively) and their study at the B3LYP/6-311++G** level of theory. Stabilities of 1—10 and 1'—10' assumed as the energy gaps between the singlet (s) and triplet (t) states (DEs-t) are compared and contrasted. With increasing number of phosphorous atoms, singlet-triplet energy gap (DEs-t), nucleophilicity (N), electrophilicity (w), chemical potential (m), band gap (DEH-L), positive natural bond orbital (NBO) charge on the Si atom, and reactivity decrease. Changes in the hydrogenation enthalpy (DHHyd) of 1—10 and 1'—10' show negative values indicating that the formation of hydrogenated divalent silylenes is exothermic (1H—10H and 1H'—10H', respectively). The positive overall change in the Gibbs free energy of reaction (DGover for the conversion of 1'—10' to 1—10, respectively) confirms that every 1'—10' is more stable than its corresponding 1—10.
Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)... more Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)-tetrazole-5-stannylenes (1R), and 1,3-di(R)-tetrazole-5-stannylenes (2R), using B3LYP/6-311++G** level of theory. Nucleophilicity, multiplicity, and stability of 1R and 2R are calculated; with R = H, methyl, ethyl, i-propyl, t-butyl, Ph, OH, methoxy, NO2, CN and CF3. Asymmetric 2H appears more nucleophilic (N 4) than its corresponding symmetric 1H isomer (N 3), mostly due to the formers higher separation of charge. The N is more sensitive to electronic effects in 1R stannylenes than those in the 2R series. Electron donating R groups increase N with Hammett ρ constants of -3.3 and -2.7 for 1R and 2R, respectively. Stannylene 2H is slightly more aromatic (NICS (1) = -10.31) than 1H (NICS (1) = -10.25). Every 1R is more stable than its corresponding 2R isomer. Every 2R is generally more nucleophilic and aromatic than its corresponding 1R. In addition the former is less electrophilic with a...
A novel magnetic chitosan hydrogel film, crosslinked with glyoxal (Fe 3 O 4 NPs/CS/glyoxal), has ... more A novel magnetic chitosan hydrogel film, crosslinked with glyoxal (Fe 3 O 4 NPs/CS/glyoxal), has been synthesized and used as an easily reusable adsorbent for 80-90 % removal of toxic Cr(VI) from water. A pseudo-second-order kinetic (with correlation coefficient R 2 > 0.99) is observed at room temperature. Characterization of the absorbent is carried out by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption isotherm is well fitted in the Langmuir equation at different temperatures [R 2 > 0.99, and 0< (Langmuir separation factor, R L ) <1]. So, our adsorbent, with the novelty of using glyoxal, and the ease of separation may be considered in Cr(VI) wastewater treatment technology.
The topology of nitrogen atoms is found to play an important role in the racemization of non-plan... more The topology of nitrogen atoms is found to play an important role in the racemization of non-planar diazacycloheptatetraenes through their corresponding singlet diazacycloheptatrienylidene transition states, at B3LYP/6-311++G**, MP2/6-31G*, MP4(SDTQ)/6-31G*//B3LYP/6-311++G**, CCSD(T)/6-31G*// B3LYP/6-311++G**, and QCISD(T)/6-31G*//B3LYP/6-311++G** levels of theory. Two types of singlet carbenes are encountered: r 2 and p 2 . The r 2 (-1 A) carbenes are aromatic and include 2,3-; 2,4-; 2,5-, and 3,4diazacycloheptatrienylidenes, while p 2 (-1 A 0 ) carbenes turn out antiaromatic and include 1,6-; 1,2-; 1,3-; 1,4-; and 1,5-diazacycloheptatrienylidenes. All singlet carbenes showed a negative force constant and except for the 1,6-isomer the rest appear of higher energy than their corresponding triplet states. Nevertheless, all allenes emerged more stable than their corresponding singlet and triplet carbenes. Due to higher energy barriers, racemization is unlikely for allenic structures including 2,3-; 2,4-; 2,5-; and 3,4-diazacyclohepta-1,2,4,6-tetraenes. In contrast, carbene-like reactivity is expected from ketenimine and carbodiimide (1,2-; 1,3-; 1,4-; 1,5-; 1,6-diazacyclohepta-1,2,4,6-tetraenes) which go through N-heterocyclic transition states that are mostly of rather lower energy.
Physica E: Low-dimensional Systems and Nanostructures, 2009
Silver nanoparticles (Ag NPs) were synthesized by g-irradiation of silver ions in aqueous solutio... more Silver nanoparticles (Ag NPs) were synthesized by g-irradiation of silver ions in aqueous solutions containing polyvinyl pyrrolidone (PVP). Increasing of g-irradiation doses from 1 to 5 kGy enhanced the concentration of Ag NPs, indicated by UV-vis analysis. The XRD and the TEM measurements showed the production of face-centered cubic (fcc) Ag NPs with a mean size of about 16 nm. The produced nanoparticles were effectively stabilized by PVP through interactions, confirmed by the FT-IR. The relatively higher antibacterial activities of Ag NPs, synthesized through g-irradiation method, against E. coli indicate their potential for practical applications as biocidal materials.
Materials Science in Semiconductor Processing, 2014
ABSTRACT Novel magnetic nanocomposites are synthesized by loading reduced graphene oxide (r-GO) w... more ABSTRACT Novel magnetic nanocomposites are synthesized by loading reduced graphene oxide (r-GO) with three brands of nanoparticles consisting of titanium dioxide (TiO2), gamma-iron(III) oxide (γ-Fe2O3), and silver (Ag) with varying amounts. The resulting Ag/TiO2/γ-Fe2O3@r-GO demonstrates synergistically enhanced visible light photocatalytic activity, on degradation of wastewater׳s toxic crystal violet (CV). Specifically, it exhibits higher photoactivity than those of neat graphene oxide (GO), TiO2@GO, γ-Fe2O3@GO, and TiO2/γ-Fe2O3@GO, possibly because of effective separation of photogenerated carriers via strongly coupled Ag/γ-Fe2O3@r-GO cocatalyst and the enrichment of organic molecules on the graphene nanosheets. A higher photocatalytic efficiency is observed when 11.5 wt% Ag nanoparticles are incorporated in TiO2/γ-Fe2O3@GO. After 3 successive cycles, the latter nanocomposite maintains 97% removal efficiency with excellent stability and easy recovery. Considering its facile preparation and high photocatalytic activity, it is hoped that this photocatalyst will find its application in various fields such as air purification and wastewater treatment. The structure and properties of Ag/TiO2/γ-Fe2O3@r-GO are characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), ultraviolet–visible spectrometry (UV–vis) and Raman spectroscopy techniques.
In regard to the worldwide interest in synthesis and application of stable carbenes, ab initio an... more In regard to the worldwide interest in synthesis and application of stable carbenes, ab initio and DFT calculations (CCSD(T)/6‐311G*//QCISD/6‐31G* and B3LYP/AUG‐cc‐pVTZ//B3LYP/6‐31 + G* levels) are employed to reach at a series of symmetrically substituted diheteroatom carbenes. In this way the multiplicity, stability, and reactivity of diethylcarbene and its saturated and unsaturated cyclic congeners are compared and contrasted to the corresponding disilyl‐, diamino‐, diphosphino‐, dioxy‐, and dithiocarbenes. The investigations reveal the enlargement of the singlet–triplet energy gaps (ΔES‐T) in the order of (amino ≈ oxy) > thio > phosphino > alkyl > silyl. The observed trend is thoroughly analyzed applying appropriate isodesmic reactions which differentiate the substituent effects on each of the singlet and triplet states of all the carbenes. In contrast to previous reports, it is found that π‐donor/σ‐acceptor amino substituents stabilize not only the singlet but also ...
Ab initio studies show the possibility of involvement of cyclic, planar, singlet and/or triplet 2... more Ab initio studies show the possibility of involvement of cyclic, planar, singlet and/or triplet 2-X-2,4,6,8-cyclononatetraenylidenes, carbenic transition states (1 Ã XÿS and/or 1 Ã XÿT ), in the conversion of cyclic conjugated non-planar allenes, 1-X-1,2,4,6,8-cyclonona-pentaenes (1 X ), to their corresponding mirror images, 1 0 X (where XZH, F, Cl and Br).
Coprecipitation of FeCl 2 and FeCl 3 produced magnetic iron nanoparticles (Fe 3 O 4 NPs). The lat... more Coprecipitation of FeCl 2 and FeCl 3 produced magnetic iron nanoparticles (Fe 3 O 4 NPs). The latter was dispersed in an acetic acid solution of chitosan (CS), and then cross-linked with glyoxal, followed by addition of polyvinyl alcohol (PVA). The resulting gel was neutralized with NaOH giving our novel Fe 3 O 4 NPs/CS/glyoxal/PVA hydrogel film. This film was used as an efficient and reusable adsorbent for the removal of toxic Cr(VI) from water, at a rather wide range of pH. The absorbent film was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and energy dispersive X-ray. Langmuir isotherm model suggested maximum Cr(VI) adsorption occurring at room temperature. Kinetic studies suggested a pseudo-second-order model for the adsorption. Our Fe 3 O 4 NPs/CS/glyoxal/PVA hydrogel is hoped to serve as a promising Cr(VI) adsorbent in wastewater treatment technology.
F 3 CA € GeAGe"GeAH, with two unpaired electrons, is the only triplet (t) ground state germylene ... more F 3 CA € GeAGe"GeAH, with two unpaired electrons, is the only triplet (t) ground state germylene found among 30 divalent species, with XHGe 3 formula, at six reasonably high ab initio and DFT levels (X = H, NH 2 , SiH 3 , and CF 3). Its corresponding singlet (s) appears at a higher energy while showing a negative force constant. The crossing angle (U) between the above s and t states is 90°. Replacement of CF 3 with H and NH 2 increases U to 120°and 160°, respectively. No crossing of the s and t states occurs for H 3 SiAGeAGe"GeAH, whose s state is its global minimum. Having X directly attached to the divalent germylene in XAGeAGe"GeAH, increases the X effects on DE s-t,X compared to the isomeric species: 3-X-1,2,3-trigermapropargylene, 3-X-1,2,3-trigermavinylidene and 2-X-1,2,3-trigermacyclopropenylidene, respectively. Nonetheless, the latter cyclic divalent species appear relatively more stable with the highest LUMO-HOMO energy gaps, while their NICS calculations show their aromatic character change as a function of X (SiH 3 > H > CF 3 > NH 2). Finally, the global minimum among the 30 isomeric XHGe 3 is found to be SiH 3 substituted singlet trigermacyclopropenylidene.
To optimize the arc fabrication of aluminum nanoparticles (Al Nps), six diverse media were probed... more To optimize the arc fabrication of aluminum nanoparticles (Al Nps), six diverse media were probed including ethylene glycol (EG), distilled water, liquid nitrogen, gaseous nitrogen, sunflower oil, and tap water (all free of any surfactant or stabilizer). These were investigated at three different currents: 50, 100 and 150 A/cm 2 . EG at 50 A/cm 2 provides the best recipe for the arc fabrication, giving the relatively purest, most dispersed and the smallest size Al Nps (26.6 nm), with the highest yield (91.5 %). Regardless of the medium used, the SEM analyses show that the size increases of Al Nps are directly proportional to the current density employed. The observed sizes for Al Nps in EG (at three different currents/A cm -2 ) are 26.6 nm (50), 64.9 nm (100), and 72.5 nm (150). Also, regardless of the current employed, the SEM analyses show different Al Nps size distributions, depending on the medium nature. The XRD extracted average sizes of the arc fabricated Al Nps show reasonable linear correlations with their corresponding elemental weight% or atomic%, acquired through energy-dispersive X-ray spectroscopy (EDX). High quantities of separable industrially significant nanoAl oxides (γ -Al 2 O 3 , Al(OH) 3 ) are fabricated along with Al Nps in tap water. In EG medium, TGA revealed only ∼7% weight loss, indicating thermal stability of the fabricated Al Nps.
A simple and effective one-pot coprecipitation of iron (II) and (III) chlorides, in the presence ... more A simple and effective one-pot coprecipitation of iron (II) and (III) chlorides, in the presence of graphene o xide (GO), resulted in the fabrication of the magnetite-GO hybrid-nanoparticles (GO@NanoFe3O4). Loading of the latter over polystyrene (PS) through in situ emulsion polymerization afforded a novel composite (GO@NanoFe3O4/PS). The TGA analysis demonstrated the anticipated thermal stabilities for NanoFe3O4@GO/PS. Furthermore, improvement of magnetic and mechanical properties of polystyrene by its loading with magnetite-GO hybrid was established through VSM and DMTA analyses.
Benzyltrimethylammonium fluorochromate (VI), BTMAFC, is synthesized by reacting benzyltrimethylam... more Benzyltrimethylammonium fluorochromate (VI), BTMAFC, is synthesized by reacting benzyltrimethylammonium bromide with an aqueous solution of CrO3 and HF. This new reagent, (C6H5CH2)(CH3)3N[CrO3F ], is used for almost quantitative conversion of oximes into the parent ketones or ...
A novel, magnetically recoverable nanocatalyst is fabricated through simple immobilization of cop... more A novel, magnetically recoverable nanocatalyst is fabricated through simple immobilization of copper(II) acetylacetonate on the surface of amine-terminated silica-coated Fe 3 O 4 nanoparticles: Cu(acac) 2 /NH 2-T/SiO 2 @Fe 3 O 4 NPs. Unambiguous bonding of Cu to the terminal amine is indicated by Xray photoelectron spectroscopy (XPS). Further characterizations are carried out by different techniques. Selectivity of this catalyst is demonstrated through one-pot synthesis of fourteen α-aminoacyl amides using Ugi four-component reaction of cyclohexyl isocyanide, acetic acid, amines and various aldehydes. Interestingly, all aromatic aldehydes react with short reaction times and high yields, but heteroaromatic aldehydes do not yield any product. Catalyst efficiency remains unaltered through three consecutive experiments.
INTRODUCTION Arc discharge is believed to play a role in originating life through experiments per... more INTRODUCTION Arc discharge is believed to play a role in originating life through experiments performed under simulated conditions after Earth first accreted from the primordial solar nebula [1]. These experiments used a highly reduced mixture of gases (methane, ammonia and ...
Singlet-triplet energy splittings for 24 GeCNX germylenic reactive intermediates are compared and... more Singlet-triplet energy splittings for 24 GeCNX germylenic reactive intermediates are compared and contrasted at 10 levels of theory: B1LYP/6-311++G**, B3LYP/6-311++G**, MP3/6-311+G*, MP3/LANL2DZ, MP2/6-311++G**, MP4(SDTQ)/6-311++G**, QCISD(T)/6-311++G**, CCSD(T)/6-311++G**, G1 and G2 (where X = H, F, Cl, and Br). Singlet (s) and/or triplet (t) GeCNX, are confined to the following three structures: 3-X-2-aza-1-germylacyclopropenylidene (1 s-X , 1 t-X), [(X-imino)methylene]germylene (2 s-X , 2 t-X), or X-cyanogermylene (3 s-X , 3 t-X). For every of these three structures the order of singlet-triplet energy separations (DE s-t,X), appears as a function of electro-negativity (F > Cl > Br > H). Fascinatingly, two triplet structures 2 t-H and 3 t-H appear more stable than their corresponding singlet states. Good linear correlations are found between the LUMO-HOMO energy gaps of the singlet germylenes, and their corresponding singlet-triplet energy separations, calculated at B3LYP/6-311++G**. Relative energies of the divalent 3 s-X and/or 3 t-X structures are plotted as a function of the divalent bond angle \X-Ge-CN, where the singlet and triplet germylenes GeCNH cross at 134°. Little germanium d orbital valence participation is found in the cyclic triplet structures 1 t-X. The global minimum, among six GeCNH species, appears to be the singlet cyclic 1 s-H. However, the global minima among the other eighteen GeCNX (X6 ¼H) species appear to be the singlet acyclic 3 s-X. Among all the calculation methods employed, B3LYP appears as the method of choice.
Si36H18, Si40H20, Si44H22, and Si48H24, respectively, at B3LYP levels (n, number of fused benzeno... more Si36H18, Si40H20, Si44H22, and Si48H24, respectively, at B3LYP levels (n, number of fused benzenoid rings). These are a brand of silicon nanorings that bear a resemblance to the shortest zig-zag silicon nanotubes (SiNTs), henceforth referred to as SiNRs. The NBO results ...
The main goal of this work is to find a more stable seven-membered ring 1H-phosphepine connected ... more The main goal of this work is to find a more stable seven-membered ring 1H-phosphepine connected to its bicyclic benzene phosphine valence tautomer after passing through a nonplanar transition state. This challenge is met by probing the impacts of substituents (X = H, F, Cl, Br, CN, ...
Zinc oxide nanoparticles (ZnO NPs, ca. 22 nm) were used as an effective catalyst in the solvent-f... more Zinc oxide nanoparticles (ZnO NPs, ca. 22 nm) were used as an effective catalyst in the solvent-free, three-component couplings of aldehydes, aromatic amines and dialkyl phosphites at room temperature to produce various a-amino phosphonates. Compared to known methods, satisfactory results were obtained with high yields through a simple experimental procedure. The catalyst was recycled and reused five times with minor decrease in its catalytic activity.
Following our quest for new divalents, we report the synthesis of P-heterocyclic silylenes (PHSis... more Following our quest for new divalents, we report the synthesis of P-heterocyclic silylenes (PHSis) by adding from one to four phosphorous atoms to saturated cyclopentasilylene (1) and unsaturated cyclopentasilylene-3-ene (1') resulting in respective PHSis (2—10 and 2'—10', respectively) and their study at the B3LYP/6-311++G** level of theory. Stabilities of 1—10 and 1'—10' assumed as the energy gaps between the singlet (s) and triplet (t) states (DEs-t) are compared and contrasted. With increasing number of phosphorous atoms, singlet-triplet energy gap (DEs-t), nucleophilicity (N), electrophilicity (w), chemical potential (m), band gap (DEH-L), positive natural bond orbital (NBO) charge on the Si atom, and reactivity decrease. Changes in the hydrogenation enthalpy (DHHyd) of 1—10 and 1'—10' show negative values indicating that the formation of hydrogenated divalent silylenes is exothermic (1H—10H and 1H'—10H', respectively). The positive overall change in the Gibbs free energy of reaction (DGover for the conversion of 1'—10' to 1—10, respectively) confirms that every 1'—10' is more stable than its corresponding 1—10.
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Papers by M. Z. kassaee