Carbonyl Bond Research Articles

High-resolution crystal structures reveal a mixture of conformers of the Gly61-Asp62 peptide bond in an oxidized flavodoxin from Bacillus cereus.

Flavodoxins (Flds) are small proteins that shuttle electrons in a range of reactions in microorganisms. Flds contain a redox‐active cofactor, a flavin mononucleotide (FMN), and it is well established that when Flds are reduced by one electron, a peptide bond close to the FMN isoalloxazine ring flips to form a new hydrogen bond with the FMN N5H, stabilizing the one‐electron reduced state. Here, we present high‐resolution crystal structures of Flavodoxin 1 from Bacillus cereus in both the oxidized (ox) and one‐electron reduced (semiquinone, sq) state. We observe a mixture of conformers in the oxidized state; a 50:50 distribution between the established oxidized conformation where the peptide bond is pointing away from the flavin, and a conformation where the peptide bond is pointing toward the flavin, approximating the conformation in the semiquinone state. We use single‐crystal spectroscopy to demonstrate that the mixture of conformers is not caused by radiation damage to the crystal. This is the first time that such a mixture of conformers is reported in a wild‐type Fld. We therefore carried out a survey of published Fld structures, which show that several proteins have a pronounced conformational flexibility of this peptide bond. The degree of flexibility seems to be modulated by the presence, or absence, of stabilizing interactions between the peptide bond carbonyl and its surrounding amino acids. We hypothesize that the degree of conformational flexibility will affect the Fld ox/sq redox potential.

Templated assembly of photoswitch Azobenzene (4-(4-nitrophenylazoyl)-phenol) by functionalization of multi-walled carbon nanotube for solar energy storage applications

In order to provide global energy applications, solar energy resources will desire remarkable advances in solar energy technologies. In this paper, the novel synthesis of the functionalization of Multi-wall Carbon Nanotube(MWCNT) with Azobenzene molecule (4-(4-nitrophenylazoyl)-phenol) by esterification method was approached. The covalent bond of carbonyl was revealed in FTIR Test (Fourier-Transform Infrared Spectroscopy). Templating Azobenzene molecules on the side wall of MWCNT increased the stored energy per Azobenzene molecule and created hybrid Solar Thermal Fuels (STF). The DSC Test (Differential Scanning Calorimetry) showed that Solar Thermal Fuels composed of a photoswitchable molecules indicates significantly increased energy storage capabilities over the generation of a nano-templated structure.

Close-looped recycling of polylactic acid used in 3D printing: An experimental investigation and life cycle assessment

Abstract The objective of this work is to investigate the potential of close-looped recycling of polylactic acid (PLA) that used in 3D printing, from the perspectives of material properties and environmental performance. A commercial grade of PLA was extruded into filament, then was subjected to fused deposition modelling (FDM) 3D printing process. The printed products were later shredded and re-extruded for repeating 3D printing cycle. Samples were taken from each repeating cycle, were characterised in terms of mechanical, rheological, molecular, thermal and morphological properties. In the experiment, the material can only be reprocessed for two 3D printing cycles, as the reprocessed material can no longer be further processing. Although little changes are observed in the mechanical properties, the viscosity measurements suggest that PLA deteriorates significantly due to the repeated FDM 3D printing cycles. The reduced viscosity values are compatible with the decrements in average molecular weights and thermal stability, the increments of carbonyl bonds, crystallinity and pinholes in the materials' surfaces. Virgin PLA was blended into the recycled material to improve the viscosities, which enables the blends 3D printable. The results of life cycle assessment approach show that the environmental burdens associated with close-looped recycling are lower than those of placing the 3D printed products in incineration or in landfill. Incineration might be another environmental alternative, due to the material embodies a relatively high calorific value; however, the material is not recuperated, thus incineration cannot satisfy the more stringent environmental legislations, in which recovery and reuse of materials are rigorously required.

Accuracy of TD-DFT Geometries: A Fresh Look.

We benchmark a panel of 48 DFT exchange-correlation functionals in the framework of TD-DFT optimizations of the geometry of valence singlet excited states. To this end, we use a set of 41 small- and medium-sized organic molecules for which reference geometries were obtained at high level of theory, typically, CC3 or CCSDR(3), with the aug-cc-pVTZ atomic basis set. For the ground-state parameters, the tested functionals provide average deviations that are small (0.010 Å and 0.5° for bond lengths and valence angles) and not very sensitive to the selected (hybrid) functional, but the errors are larger for the most polarized bonds (CO, CN, and so on). Nevertheless, DFT has a tendency to provide too compact distances, a trend slightly enhanced for functionals including a large amount of exact exchange. The average errors largely increase when going to the excited-state for most bond types, that is, TD-DFT delivers less accurate excited-state distances than DFT for ground state. In particular TD-DFT combined with hybrid functionals provides significantly too short CO and CS/CSe bonds with respective average errors in the -0.026/-0.052 Å and -0.015/-0.082 Å ranges, depending on the selected hybrid functional. For the carbonyl bonds, the sizes of the TD-DFT deviations obtained when selecting standard hybrid functionals are of the same order of magnitude as the EOM-CCSD ones.

Using poly(l-lactic acid) and poly(ɛ-caprolactone) blends to fabricate self-expanding, watertight and biodegradable surgical patches for potential fetoscopic myelomeningocele repair.

Our study focuses on the development and characterization of a self-expanding, watertight and biodegradable patch for fetoscopic myelomeningocele (MMC) prenatal repair. We fabricated poly(l-lactic acid) (PLA) and poly(ɛ-caprolactone) (PCL) blend films by solution casting. Formulation c with average glass transition temperature of 37.6 ± 1.2°C was chosen for temporospatial recovery. Favorable results from surface studies reflected homogeneous dispersion of polymers in the blend. The cytotoxicity was studied in human foreskin fibroblasts. The blend film was cytocompatible, evidenced by matching percentage of live cells in exposed and control solutions. Subsequently, liquid water permeability experiments confirmed watertight nature of films. Finally, in vitro degradation was investigated in phosphate buffered saline (PBS) and amniotic fluid (AF) separately for 16 weeks. Similar weight loss (n = 6, p = 0.912) and significantly different (n = 3, p = 0.025) surface roughness was observed in PBS and AF, respectively, at 16 weeks. Functional group analysis displayed increasing carbonyl and hydroxyl bonds in PBS and AF, respectively, over time, indicating progression of hydrolytic degradation. Favorable characterization results provide strong evidence to employ PLA-PCL blend films as surgical patches in fetoscopic MMC repair. Designed patch serves as standalone system to successfully tackle impending hurdles of MMC repair and proves to be a superior alternative compared to existing patches. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 295-305, 2019.

Furfural to Furfuryl Alcohol: Computational Study of the Hydrogen Transfer on Lewis Acidic BEA Zeolites and Effects of Cation Exchange and Tetravalent Metal Substitution

The hydrogen transfer of furfural to furfuryl alcohol with i-propanol as the hydrogen source over cation-exchanged Lewis acidic BEA zeolite has been investigated by means of density functional calculations. The reaction proceeds in three steps. First the O-H bond of i-propanol is broken to form a propoxide intermediate. After that, the furylmethoxy intermediate is formed via hydrogen transfer process, and finally furylmethoxy abstracts the proton to form the furfuryl alcohol product. The second step is rate-determining by requiring the highest activation energy (23.8 kcal/mol) if the reaction takes place on Li-Sn-BEA zeolite. We find that the catalytic activity of various cation-exchanged Sn-BEA zeolites is in the order Li-Sn-BEA > Na-Sn-BEA > K-Sn-BEA. The lower activation energy for Li-Sn-BEA compared to Na-Sn-BEA and K-Sn-BEA can be explained by the larger charge transfer from the carbonyl bond to the catalyst, leading to its activation and to the attraction of the hydrogen being transferred. The larger charge transfer in turn is due to the smaller gap between the energies of furfural HOMO and the zeolite LUMO in Li-Sn-BEA, compared to both Na-Sn-BEA and K-Sn-BEA. In a similar way, we also compare the catalytic activity of tetravalent metal centers (Sn, Zr, and Hf) substituted into BEA and find in the order Zr ≥ Hf > Sn, based on activation energies. Finally we investigate statistically which property of the reactants is a suitable descriptor for an approximative prediction of the reaction rate in order to be able to quickly screen promising catalytic materials for this reaction.

Surface functionalization of highly luminescent carbon nanodots from Dioscorea hispida with polyethylene glycol and branched polyethyleneimine and their in vitro study

Synthesized carbon dots (C-dots) from Dioscorea hispida (Gadong tuber) starch were modified with passivating agents such as O,O-bis(3-aminopropyl)polyethylene glycol 1500 (PEG1500N) and branched polyethyleneimine (BPEI) to increase the functional efficiency of C-dots to be used in biological investigations. After surface modification, the C-dots decreased in size from 6–25 to 3–20 nm without changing their morphology. The modified C-dots were fluorescent, and the fluorescence peak gradually shifted to a longer excitation wavelength (from 420 to 500). Upon modification, thereby elucidating a competitive quantum yield of 15% (C-dots-PEG1500N) and 12.6% (C-dots-BPEI). The UV-visible spectrum of the C-dots modified with PEG1500N contained an absorption peak at 290 nm, whereas, that of the C-dots modified with BPEI contained peak at 360. Fourier-transform infrared analysis showed a peak at 1700 cm−1 (C-dots-PEG1500N) and 1697 cm−1 (C-dots-BPEI) that corresponds to the amide (HCONH) carbonyl bond, indicating that PEG1500N and BPEI had been successfully passivated on the surface of C-dots. To examine photothermal response, irradiation was carried out for 5 min using three different instruments which is UV-lamp (365 nm), visible lamp and laser (532 nm, 1 W/cm2) where temperature for each sample increased respectively. C-dots demonstrated not losing their luminescent properties upon irradiation to UV-lamp and laser for 30 min. Contrary, the intensity of fluorescence reduced when it exposed to the visible lamp for the same period. In vitro studies of the modified C-dots with zebrafish (Danio rerio) revealed that C-dots-PEG1500N is non-toxic while C-dots-BPEI is highly toxic to the fish embryos. Significantly, this study has successfully demonstrated that Gadong tuber starch can be used as a starch-based modifier for C-dots; which possibly can be utilized as a nanocarrier with thermal sensing properties.

A density functional theory study on the interaction between UO22+ and the carbamoylphosphoramidic acid ligand for uranium extraction from seawater

Phosphorylurea molecules, which contain both phosphoryl and carbonyl groups, are considered efficient extractants for UO22+. This study aims to explain the complexation of UO22+ with carbamoylphosphoramidic acid (CPO), a simple model for phosphorylurea, for ligand design for uranium recovery from seawater using density functional theory calculations, natural bond order analysis, and the quantum theory of atoms in molecules. The results showed that, when CPO acts as a monodentate ligand, the affinity of phosphoryl for UO22+ is stronger than that of carbonyl, and CPO coordinates with UO22+ through the phosphoryl oxygen atom. When CPO serves as a bidentate ligand, both the phosphoryl and carbonyl oxygen atoms connect to UO22+, and the U–O(carbonyl) bond plays a more important role than the U–O(phosphoryl) bond in the interaction between UO22+ and CPO. This paradox may be caused by the significant charge transfer from the U–O(carbonyl) π bond orbital to the C–N σ antibond orbital of the bidentate CPO. The NH spacer between the phosphoryl and carbonyl groups could ensure the delocalization of the electron system of the molecule. The bidentate binding motif is favored by entropy and opposed by enthalpy, while the monodentate binding motif is favored by enthalpy and opposed by entropy. Ultimately, the bidentate binding motif is more favorable than the monodentate one. As expected, the interaction between UO22+ and the deprotonated CPO is stronger than that between UO22+ and the neutral CPO. Comparing the interaction between UO22+ and CPO with that between UO22+ and N-phenylcarbamoylphosphoramidic acid (PhCPO), formed by replacing one hydrogen atom from the terminal nitrogen atom of CPO with a phenyl group, the phenyl substituent at the terminal nitrogen atom of PhCPO shows a slightly negative effect on the interaction between UO22+ and PhCPO.

Ligand Effect on Bonding in Gold(III) Carbonyl Complexes.

We quantitatively assess the Dewar-Chatt-Duncanson (DCD) components of the Au(III)-CO bond and the charge density polarization at the CO, in a series of neutral, cationic, and dicationic bis- and monocyclometalated gold(III) complexes via charge-displacement (CD) analysis. A striking feature concerns the very small net electron charge flux from CO to the metal fragment which is unexpectedly stable toward both the charge of the complex and the oxidation state of gold (I, III). All systems exhibit a similar trend for the σ charge rearrangement in the region of the carbonyl bond, where, by contrast, the π back-donation trend variation is large, which is strictly correlated to the change in CO bond distance and the shift in CO stretching frequencies, in close analogy with the gold(I) carbonyl complexes. In the whole series of gold(III) compounds, a large Au(III) ← CO σ donation is measured (from 0.19 to 0.31 electrons), as well as a significant Au(III) → CO π back-donation (from -0.09 to -0.22 electrons), which however is not generally able to completely balance the polarization of the CO π electrons in the direction from oxygen to carbon (C ← O) induced by the presence of the metal fragment [LAu(III)]0/+1/+2. Surprisingly, all the gold(III) complexes in the series are characterized by a very small anisotropy in the Au(III) → CO in-plane and out-of-plane π back-donation components, in sharp contrast with the marked anisotropy found before for the experimentally characterized [(C^N^C)Au(III)CO]+ complex. A first attempt to figure out a rationale on the bonding/reactivity relationship for Au(III)-CO is made by performing a comparative study with an isostructural [(N^N^C)Pt(II)CO]+ complex in a model water-gas shift (WGS) reaction.

The Coordination and Luminescence of the Eu(III) Complexes with the Polymers (PMMA, PVP).

The rare earth complexes and the polymers can be made into composite nanofibers through electrospinning. The fluorescence intensity of these fiber composites is much higher than that of the rare earth complexes. By changing the mixed proportion of polymethyl methacrylate (PMMA) and complexes, nanofiber materials were prepared. Then, by measuring their fluorescence intensity, it is found that the carbonyl bond of PMMA may have coordinated with the rare earth ions and enhanced the luminescence intensity of them. Then, a series of experiments were designed to study their coordination and luminescence mechanism. The coordination mechanism of the polymers with carbonyl groups and the rare earth complexes was explained by Eu(TFT)3(TPPO), Eu(TFT)3(TPPO)2, Eu(PFP)3(TPPO), Eu(PFP)3(TPPO)2, and polyvinyl pyrrolidone (PVP) dissolved in chloroform solution, where TFT means 2-(2,2,2-trifluoroethyl)-1-tetralone, PFP means 2-(2,2,3,3,3-Pentafluoropro-panoyl)-3,4-dihydronaphthalen-1(2H)-one and TPPO means phosphine oxide. The coordination of PVP and the rare earth complexes in solution was studied, and it was found that the fluorine atoms of the ligand had a significant impact on the aggregation-induced effect of the composites. The electron transitioned in the polymers and the complexes were enhanced greatly by the coordination. The colors of emission light could be adjusted by the coordination of the polymers and the rare earth complexes.

2-[(4-Chloro-phen-yl)sulfan-yl]-2-meth-oxy-1-phenyl-ethan-1-one: crystal structure and Hirshfeld surface analysis.

The title compound, C15H13ClO2S, comprises (4-chloro-phen-yl)sulfanyl, benzaldehyde and meth-oxy residues linked at a chiral methine-C atom (the crystal is racemic). A twist in the methine-C-C(carbon-yl) bond [O-C-C-O torsion angle = 19.3 (7)°] leads to a dihedral angle of 22.2 (5)° between the benzaldehyde and methine+meth-oxy residues. The chloro-benzene ring is folded to lie over the O atoms, with the dihedral angle between the benzene rings being 42.9 (2)°. In the crystal, the carbonyl-O atom accepts two C-H⋯O inter-actions with methyl- and methine-C-H atoms being the donors. The result is an helical supra-molecular chain aligned along the c axis; chains pack with no directional inter-actions between them. An analysis of the Hirshfeld surface points to the important contributions of weak H⋯H and C⋯C contacts to the mol-ecular packing.

Ultrathin Polyelectrolytes for Solid State 3D Lithium Microbatteries

Lithium ion batteries are widely used for portable electronics, particularly laptops and mobile phones, due to their superior energy and power densities. As modern microelectronic devices and microelectronic mechanical systems (MEMS) advance further, the bottleneck to further miniaturization is often energy storage.1 While solid state thin film batteries offer remarkable electrochemical performance and long term stability, they are limited by areal capacity (mAh/cm2).2 Solid state three dimensional lithium ion micro-batteries (3D micro-batteries, for short) are an attempt to realize the exceptional electrochemical performance of thin film batteries by fabricating solid state lithium ion cells on high specific surface area. The challenge to realizing these battery designs is the preparation of conformal, ultrathin solid-state electrolytes that physically separate the two electrodes while allowing rapid ion transport. Using initiated chemical vapor deposition, 1µm-thick crosslinked polymer thin films composed of poly (methacrylic acid-co-ethylene glycol diacrylate) were synthesized. These films were transformed to lithium-bearing polyelectrolytes through H+/Li+ ion exchange in a 1M LiOCH3 solution in methanol. Fourier transform infrared spectroscopy (FTIR) characterization was used to determine the chemical composition of the copolymer film and confirm successful ion exchange through analysis of the vibrational stretch of the carbonyl (C=O) bonds in the acidic and salt forms of the polymer electrolyte. The effect of crosslinking densities in these films (the mole fraction of ethylene glycol diacrylate) on electrochemical properties was studied. The optimal ionic conductivity of the Li+-exchanged polymer was determined to be 3.75x10-7 S/cm at 60°C with an activation energy of 0.8785eV. The electrochemical stability of this electrolyte is still under investigation through cycling in thin film cells where vapor-deposited lithium metal as the anode and Au as the working electrode. Current efforts to further enhance ionic conductivity and to integrate these materials into full solid state lithium metal batteries will also be presented. 1. Letiche, M.; Eustache, E.; Freixas, J.; Demortiere, A.; De Andrade, V.; Morgenroth, L.; Tilmant, P.; Vaurette, F.; Troadec, D.; Roussel, P.; Brousse, T.; Lethien, C., Atomic Layer Deposition of Functional Layers for on Chip 3D Li-Ion All Solid State Microbattery. Adv. Energy Mater. 2017, 7 (2), 12. 2. Ferrari, S.; Loveridge, M.; Beattie, S. D.; Jahn, M.; Dashwood, R. J.; Bhagat, R., Latest advances in the manufacturing of 3D rechargeable lithium microbatteries. Journal of Power Sources 2015, 286, 25-46.

Crystal structure of an iridium(III) complex of the [C(dppm)2] PCP pincer ligand system and its conjugate CH acid form.

After the successful creation of the newly designed PCP carbodi-phospho-rane (CDP) ligand [Reitsamer et al. (2012 ▸). Dalton Trans.41, 3503-3514; Stallinger et al. (2007 ▸). Chem. Commun. pp. 510-512], the treatment of this PCP pincer system with the transition metal iridium and further the analysis of the structures by single-crystal diffraction and by NMR spectroscopy were of major inter-est. Two different iridium complexes, namely (bis-{[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}methane-κ3P,C,P')carbonyl-chlorido-hydridoiridium(III) chloride di-chloro-methane tris-olvate, [IrIII(CO){C(dppm)2-κ3P,C,P'}ClH]Cl·3CH2Cl2 (1) and the closely related (bis-{[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}methanide(1+)-κ3P,C,P')carbonyl-chlorido-hy-dridoirid-ium(III) dichloride-hydro-chloric acid-water (1/2/5.5), [IrIII(CO){CH(dppm)2-κ3P,C,P')ClH]Cl}2 (2), have been designed and both complexes show a slightly distorted octa-hedral coordinated IrIII centre. The PCP pincer ligand system is arranged in a meridional manner, the CO ligand is located trans to the central PCP carbon and a hydride and chloride are located perpendicular above and below the P2C2 plane. With an Ir-CCDP distance of 2.157 (5) Å, an Ir-CO distance of 1.891 (6) Å and a quite short C-O distance of 1.117 (7) Å, complex 1 presents a strong carbonyl bond. Complex 2, the corresponding CH acid of 1, shows an additionally attached proton at the carbodi-phospho-rane carbon atom located anti-periplanar to the hydride of the metal centre. In comparison with complex 1, the Ir-CCDP distance of 2.207 (3) Å is lengthened and the Ir-C-O values indicate a weaker trans influence of the central carbodi-phospho-rane carbon atom.

Fourier Transform Microwave Spectroscopic and ab Initio Study of the Rotamers of 2-Fluorobenzaldehyde and 3-Fluorobenzaldehyde.

The rotational spectra of 2-fluorobenzaldehyde (2-FBD) and 3-fluorobenzaldehyde (3-FBD) were recorded using Fourier transform microwave (FTMW) spectroscopy from 4 to 26 GHz. Two planar rotamers were observed for each species that correspond to structures in which the carbonyl bond is directed toward (O-cis) or away from (O-trans) the C1-C2 bond. Observation of transitions due to heavy atom isotopes (13C, 18O) in natural abundance allowed derivation of the ground state effective (r0) structures and mass dependence (rm) structures for the lowest energy rotamer of 2-FBD (O-trans) and both rotamers of 3-FBD, which compare favorably with ab initio estimates of the equilibrium (re) geometries at the MP2/aug-cc-pVTZ level. The resultant parameters are consistent with the introduction of bond length alternation in the benzene ring, which is dependent on the orientation of the aldehyde group. Careful study of the experimental structure and results of natural bond orbital (NBO) analysis do not support the presence of intramolecular hydrogen bonding as the source of its stabilization of O-trans 2-FBD over its cis counterpart. Furthermore, calculations of the interconversion pathways between rotamers suggest that despite being 9.39 kJ/mol higher in energy, the O-cis 2-FBD moiety is metastable in the molecular beam, which has allowed the observation of its microwave spectrum for the first time.

Probing electrochemical reactions in organic cathode materials via in operando infrared spectroscopy

Organic materials are receiving an increasing amount of attention as electrode materials for future post lithium-ion batteries due to their versatility and sustainability. However, their electrochemical reaction mechanism has seldom been investigated. This is a direct consequence of a lack of straightforward and broadly available analytical techniques. Herein, a straightforward in operando attenuated total reflectance infrared spectroscopy method is developed that allows visualization of changes of all infrared active bands that occur as a consequence of reduction/oxidation processes. In operando infrared spectroscopy is applied to the analysis of three different organic polymer materials in lithium batteries. Moreover, this in operando method is further extended to investigation of redox reaction mechanism of poly(anthraquinonyl sulfide) in a magnesium battery, where a reduction of carbonyl bond is demonstrated as a mechanism of electrochemical activity. Conclusions done by the in operando results are complemented by synthesis of model compound and density functional theory calculation of infrared spectra.

Development and characterization of a synthetic PVC/DEHP myocardial tissue analogue material for CT imaging applications

A simple myocardial analogue material has great potential to help researchers in the creation of medical CT Imaging phantoms. This work aims to outline a Bis(2-ethylhexyl) phthalate (DEHP) plasticizer/PVC material to achieve this. DEHP-PVC was manufactured in three ratios, 75, 80, and 85% DEHP by heating at 110 °C for 10 min to promote DEHP-PVC binding followed by heating at 150 °C to melt the blend. The material was then tested utilizing FTIR, tensile testing, dynamic mechanical analysis and imaged with computed tomography. The FTIR testing finds the presence of C-CL and carbonyl bonds that demonstrate the binding required in this plasticized material. The tensile testing finds a modulus of 180–20 kPa that increases with the proportion of plasticizer. The dynamic mechanical analysis finds a linear increase in viscoelastic properties with a storage/loss modulus of 6/.5–120/18 kPa. Finally, the CT number of the material increases with higher PVC content from 55 to 144HU. The 80% DEHP-PVC ratio meets the mechanical and CT properties necessary to function as a myocardial tissue analogue.

Influence of imidazolium-based ionic liquids on coal oxidation

In order to find the ionic liquids (ILs) which can significantly suppress coal oxidation, nine imidazolium-based ILs, [EMIm][BF4], [EMIm]Ac, [BMIm][BF4], [BMIm]Ac, [AMIm][BF4], [HOEtMIm][BF4], [HOEtMIm][NTf2], [AOEMIm][BF4] and [EOMIm][BF4], were used to treat lignite sample to reveal the inhibitory effect of ILs on coal oxidation activity. The TGA results showed that the ILs can reduce the mass loss of coal, of which the ILs [HOEtMIm][BF4] and [HOEtMIm][NTf2] showed the strongest reducing effect, while the IL [AMIm][BF4] showed the weakest reducing effect. Differential thermal analysis (DTA) results indicated that the heat release of [HOEtMIm][BF4] and [HOEtMIm][NTf2]-treated coal were very less. At the same time, the oxidation reactions of the two coals were delayed. IR results showed that ILs treatment can effectively destroy the associated hydroxyl in coal and change the content of carbonyl and ether bonds. In the process of coal oxidation, the oxidation activity of hydrogen bonding, ether bonds in [HOEtMIm][BF4] and [HOEtMIm][NTf2]-treated coal were weakened significantly at the initial oxidation process. With the oxidation processing, the content of generated carbonyl was reduced. The micro mechanism of the reduced coal oxidation activity was ascribed to the weaker oxidation activity of the ether bonds and the inhibited formation of the carbonyl groups.

PEMBUATAN KARBON AKTIF DARI KULIT SALAK (Salacca Zalacca) DENGAN PROSES FISIKA MENGGUNAKAN UAP DENGAN PEMANAS MICROWAVE


 This study aimed to determine the best adsorption capacity, compounds contained in activated carbon and burn off that produced. In this study, activated carbon have been prepared from the bark of Salacca zalacca by physically activating using a microwave. The 70 gram bark of Salacca zalaccawas pyrolised in a furnace with flowing gas N2 with temperature 500 oC for 120 minutes followed by microwave activation at 2450 MHz with power 600 W, 800 W and 1000 W for 20 minutes, 40 minutes and 60 minutes. The results showed the best burn off on microwave power 1000 W with 60 minutes activation time of 90,25%. The best activated carbon adsorption capacity at 800 W microwave power for 20 minutes is 19,96 mg/g. The best allowanced percentage at 800 W microwave power with 20 minutes activation time is 99,82%. Characterization of Fourier Transform Infra-Red (FITR) showed the presence of C=O (carbonyl) bonds indicating the presence of carbon-active substances. After pyrolysis forms a C≡C (Alkuna) bond which indicated more carbon was produced. This is supported by the characterization of Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) showing the surface morphology of rough and irregular activated carbon and the amount of carbon and oxide content on activated carbon of 44,44% and 28,54% sequentially.

Crystal Structure and Cyclic Voltammetric Studies on the Metal Complexes of N-(Dimethylcarbamothioyl)-4-fluorobenzamide

We synthesized N-(dimethylcarbamothioyl)-4-fluorobenzamide compound and its copper(II) and nickel(II) complexes. The structures of compounds have been characterized by elemental analysis and spectral data (IR, 1H NMR). Furthermore, crystal and molecular structure of the synthesized complexes have been identified by using single crystal X-ray diffraction data. In the complexes formation the metal atom was coordinated via two sulfur atoms and two oxygen atoms. The single crystal structure of copper(II) and nickel(II) complex exhibits slightly distorted square planar geometry. The oxygen atoms are in a cis configuration. It appeared that the lengths of the thiocarbonyl and carbonyl bonds are longer than the average for C=S and C=O; meanwhile the C‐N bonds in the complex ring appeared to be shorter than the average for C‐N single bonds. These data show that C-O, C-S, and C-N bond lengths of the complexes suggest considerable electronic delocalization in the chelate ring. All bond lengths and angles obtained as a result of the analyses are found to be within experimental error limits. The obtained crystal analysis data shows that the structure of complex compounds is compatible with similar compounds in literature. Electrochemical behavior of complexes has been investigated by cyclic voltammetry technique in aprotic media. From the cyclic voltammetric investigation, both of the complexes have demonstrated electroactive properties.

Isomer activation controls stereospecificity of class I fructose-1,6-bisphosphate aldolases

Fructose-1,6-bisphosphate (FBP) aldolase, a glycolytic enzyme, catalyzes the reversible and stereospecific aldol addition of dihydroxyacetone phosphate (DHAP) and d-glyceraldehyde 3-phosphate (d-G3P) by an unresolved mechanism. To afford insight into the molecular determinants of FBP aldolase stereospecificity during aldol addition, a key ternary complex formed by DHAP and d-G3P, comprising 2% of the equilibrium population at physiological pH, was cryotrapped in the active site of Toxoplasma gondii aldolase crystals to high resolution. The growth of T. gondii aldolase crystals in acidic conditions enabled trapping of the ternary complex as a dominant population. The obligate 3(S)-4(R) stereochemistry at the nascent C3-C4 bond of FBP requires a si-face attack by the covalent DHAP nucleophile on the d-G3P aldehyde si-face in the active site. The cis-isomer of the d-G3P aldehyde, representing the dominant population trapped in the ternary complex, would lead to re-face attack on the aldehyde and yield tagatose 1,6-bisphosphate, a competitive inhibitor of the enzyme. We propose that unhindered rotational isomerization by the d-G3P aldehyde moiety in the ternary complex generates the active trans-isomer competent for carbonyl bond activation by active-site residues, thereby enabling si-face attack by the DHAP enamine. C-C bond formation by the cis-isomer is suppressed by hydrogen bonding of the cis-aldehyde carbonyl with the DHAP enamine phosphate dianion through a tetrahedrally coordinated water molecule. The active site geometry further suppresses C-C bond formation with the l-G3P enantiomer of d-G3P. Understanding C-C formation is of fundamental importance in biological reactions and has considerable relevance to biosynthetic reactions in organic chemistry.