Position Of Functional Groups Research Articles

Interaction of dopants and functional groups adsorbed on the carbon fullerenes: Computational study

Abstract We apply density functional theory to study the effective interaction between dopant atoms (B, N, Si, P) and functional groups (H, F, Cl, OH) on the surface of carbon fullerenes. Both dopant atoms and functional groups strongly interact through the carbon cage even in diametrically opposite positions. Interaction energies distribute in a wide range from 0.1 to 2 eV and non-monotonically depend on fullerene size and distance between dopants or functional groups. Such interaction cannot be described as a simple Coulomb repulsion or sum of dopants binding energies and cage strain energy. We identify some general trends in relative positions of dopants or functional groups in low-energy isomers. Para position of two functional groups is the most feasible for C60 and larger cages. For lower fullerenes, ortho or other spaced positions may be more preferable. The interaction of foreign atoms embedded into the carbon cages is more complicated. The best relative positions intricately depend on the cage size and chemical nature of dopants. As a rule, ortho and para locations are feasible for C60 and larger cages. However, some exceptions are observed. The effect of thermal vibrations on the considered interactions in doped or functionalized fullerenes is negligible in the temperature range from 300 to 1000 K.

Singlet oxygen production abilities of oxidated aromatic compounds in natural water

Singlet oxygen (1O2) is well known to be formed through energy transfer from excited state organic matters to O2, playing an important role in the transformations of contaminants. However, the contribution of small oxidated aromatic compounds (OACs) to the production of 1O2 in surface water is unclear. In this study, 28 OACs were selected to investigate the correlations between their photochemical production abilities of 1O2 and molecular structures. Our results showed that the steady-state concentrations and quantum yields of 1O2 (Φ1O2) generated by OACs were in the range of 7.0 × 10−14–1.4 × 10−12 M and 2.2 × 10−4–4.7 × 10−2, respectively, indicating that the photochemical production abilities of 1O2 by OACs varied greatly with types and positions of functional groups on the molecule. More importantly, the observed photochemical production of 1O2 was most notable in cases of molecules containing –OCH3 group and benzoquinone. A good quantitative structure-property relationship model was established between 1O2 producing ability, energy of the lowest unoccupied molecular orbitals (ELUMO) and the most positive net charge of hydrogen atoms (qH+) of OACs. In addition, the role of 1O2 produced by 2, 6-dimethoxy-1, 4-benzoquinone, the OAC with the highest Φ1O2, in the photodegradation of organic contaminants was validated by the enhanced degradation of atorvastatin under simulated sunlight, suggesting that OACs ubiquitously existed in surface water may greatly affect the fate and ecological risks of organic contaminants.

Spray, atomization and combustion characteristics of oxygenated fuels in a constant volume bomb: A review

Biofuels have extensive available resources and have an immense potential as promising alternative fuels for automobile. The application advantages of biofuels are mainly reflected as particulate matter (PM) reduction, carbon neutral, greenhouse gases reduction, waste utilization, energy and economic security, and fuel pluralism. Based on the understanding of molecular structure effects of biofuels on soot formation and particles morphology, the effects of alcohols, ethers, esters and biodiesel on spray and combustion process in constant volume bomb in recent years are retrospectively analyzed in this paper. For the mixture, macromolecular ester fuels and polyoxymethylene dimethyl ether (PODE) are conducive to the improvement of liquid spray, while biodiesel, small molecules, dimethyl ether (DME) and alcohols are reversed. Alcohols are advantageous to the extension of mixing time and the increasing of vapor-phase mixture. Through the influence integrated assessment, alcohols show the best performance on the spray, atomization and combustion, while biodiesels show the worst. But in terms of combustion, PODE is the best choice without considering spray and atomization. For binary alternative-diesel fuel blends, methanol or butanol is the best additive based on synthetically considerations on spray, atomization and combustion. To meet the requirements of the fuel application of diesel engine, ternary fuel or even quaternary fuel have been proposed and explored. This review can help to form a systematic understanding on fuel recombining and obtain the guide of clean and efficient fuel formulation for diesel engine. • Spray and combustion in constant volume bomb fueled with oxygenated fuels are reviewed. • Spray and combustion of different oxygen functional group fuels are analyzed. • Spray and combustion of different carbon chain length fuels are analyzed. • Spray and combustion of biodiesel from different sources are analyzed. • Spray and combustion of different functional group position esters are analyzed.

(Invited) Hybrid Van Der Waals Heterostructures: From Fundamentals to Applications

2D materials are held together by weak interplanar van der Waals (vdW) interactions. The incorporation of molecules in such materials holds an immense potential to understand and modify the fundamental physical properties of the pristine materials while creatin new artificial materials. Whilst nature offers a finite number of 2D materials, an almost unlimited variety of molecules can be designed and synthesized with predictable functionalities. The possibilities offered by systems in which continuous molecular layers are interfaced with inorganic 2D materials to form hybrid organic/inorganic van der Waals heterostructures (H-vdWH) are emphasized. Similar to their inorganic counterpart, the hybrid structures have been exploited to suggest novel device architectures. Moreover, specific molecular groups can be employed to modify intrinsic properties and confer new capabilities to 2D materials. In particular, I will highlight how molecular self-assembly at the surface of 2D materials can be mastered to achieve precise control over position and density of (molecular) functional groups, paving the way for a new class of hybrid functional materials.In particular, within such vdW heterostructures, currently assembled by mechanical superposition of different layers, periodic potentials naturally occur at the interface between the 2D materials. These potentials significantly modify the electronic structure of the individual 2D components within the stack and their alignment, thus offering the possibility to build up hybrid and novel materials with unique properties.Also, I will show how the presence of ordered supramolecular assemblies bearing different functional groups can modify the pristine Shubnikov-De Haas oscillations occurring in graphene.Finally, an example will be given of how a carefully designed H-vdWH could be used for sensing of different biomarkers.

친환경적 살충제 개발을 위한 비스테로이드성 Ecdysone 작용제들의 화학구조 특성 비교 연구

The relationship between physicochemical and molecular structural properties of non-steroidal ecdysone agonists and their bioactivity was investigated in this study. 2 Dibenzoylhydrazines including RH 5849 and tebufenozide, 1 non-dibenzoylhydrazine, DTBHIB and 1 naturally found agonist, 8-O-acetylharpagide were selected and their molecular physicochemical parameter values such as Log P, hydrophilic-lipophilic balance(H.L.B.), hydrogen bond(H.B.), dipole moment(D.M.), and connectivity/kappa index and distribution of electronic charge were calculated/drawn using computer program to be compared. DTBHIB showed physicochemical and steric properties more similar to dibenzoylhydrazines than 8-O-acetylharpagide. Overally, non-steroidal ecdysone agonists showed an increasing tendency of bioactivity with the increase of their hydrophobicity within a certain range. It was also shown that dibenzoylhydrazines and DTBHIB share the common distribution pattern of molecular electronic charge which is offered by -C=O linked with the left benzene ring. These results suggest that bioactivity of non-steroidal ecdysone agonists is affected combinedly by physico-chemical properties such as hydrophilicity of the ligand, position and steric orientation of functional groups and distribution of electronic charge in the molecule, not only by the number of -OH in the molecule and resulting possibility of hydrogen bond with receptors.

Poly(arylene ether ketone) with tetra quaternary ammonium carbazole derivative pendant for anion exchange membrane

As a key component of fuel cell, the anion exchange membrane (AEM) must present high durability, which includes dimensional stability，thermal stability，and alkali resistance. In order to obtain AEM with high performance, besides stable structure, the polymer should have high molecular weight and advantaged functional group position. In this work, a novel high molecular weight polymer precursor, poly(arylene ether ketone) (PAEK) with iodobenzene pendent was designed and prepared. And then, the function tetra-quaternary ammonium carbazole was introduced onto polymer backbone by Ullmann grafting reaction and quaterisation. The obtained membranes exhibited good dimensional stability, appropriate thermal stability and high ion conductivity. In addition, the membranes exhibited good alkaline resistance, as it still kept 90% of the conductivity after immersion in 4M NaOH solution for a week. Over all, the membranes in this work are promising for anion exchange membrane fuel cell.

Large scale chemical functionalization of locally curved graphene with nanometer resolution

Anchoring various functional groups to graphene is the most versatile approach for tailoring its functional properties. To date, one must use a special tunneling microscope for attaching a molecule at a specific position on the graphene with resolution better than several hundred nanometers, however, achieving this resolution is impossible on a large scale. We demonstrate for the first time that chemical functionalization can be achieved with nanometer resolution by introducing strain with nanometer scale modulation into a graphene layer. The spatial distribution of the strain has been achieved by transferring a single-layer graphene (SLG) onto a substrate decorated by a few nm large nanoparticles (NPs). By changing the number of NPs on the substrate, the amount of locally strained SLG increases, as confirmed by atomic force microscopy (AFM) and Raman spectroscopy investigations. We further carried out hydrogenation and fluorination on the SLG with increasing amount of nanoscale corrugations. Raman spectroscopy, AFM and X-ray photoelectron spectroscopy revealed unambiguously that the level of functionalization increases proportionally with the number of NPs, which means an increasing number of the locally strained SLG. Our approach thus enables control of the amount and the position of functional groups on graphene with nanometer resolution.

Azo dye degrading bacteria tolerant to extreme conditions inhabit nearshore ecosystems: Optimization and degradation pathways

Nearshore ecosystems are transitional zones, and they may harbor a diverse microbial community capable of degrading azo dyes under extreme environmental conditions. In this study, thirteen bacterial strains capable of degrading eight azo dyes were isolated in nearshore environments and characterized using high throughput 16 S rRNA sequencing. The results of this study demonstrate that the biodegradability of azo dyes was influenced by their chemical structure and position of functional groups as well as the type of bacteria. The decolorization rate of Methyl Orange (95%) was double that of the heavier and sterically hindered Reactive Yellow 84 (<40%). Shewanella indica strain ST2, Oceanimonas smirnovii strain ST3, Enterococcus faecalis strain ST5, and Clostridium bufermentans strain ST12 demonstrated potential application in industrial effluent treatment as they were tolerant to a wide range of environmental parameters (pH: 5–9, NaCl: 0–70 g L−1, azo dye concentration: 100–2000 mg L−1) including exposure to metals. Analysis of the transformation products using GC-MS revealed that different bacterial strains may have different biotransformation pathways. This study provides critical insight on the in-situ biotransformation potential of azo dyes in marine environments.

Experimental Study of the Combustion and Emission Characteristics of Lower Alcohols in a Constant Volume Vessel

The synergistic effects of chain length, functional group position, and equivalence ratio on the combustion and emission characteristics of lower alcohols were investigated in a constant volume ves...

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media.

Pathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed. Herein, we exploit positional isomerism as a new molecular design strategy for pathway control in aqueous self‐assembly. We compare the self‐assembly of two carboxyl‐functionalized amphiphilic BODIPY dyes that solely differ in the relative position of functional groups. Placement of the carboxyl group at the 2‐position enables efficient pairwise H‐bonding interactions into a single thermodynamic species, whereas meso‐substitution induces pathway complexity due to competing hydrophobic and hydrogen bonding interactions. Our results show the importance of positional engineering for pathway control in aqueous self‐assembly.

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

AbstractPathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed. Herein, we exploit positional isomerism as a new molecular design strategy for pathway control in aqueous self‐assembly. We compare the self‐assembly of two carboxyl‐functionalized amphiphilic BODIPY dyes that solely differ in the relative position of functional groups. Placement of the carboxyl group at the 2‐position enables efficient pairwise H‐bonding interactions into a single thermodynamic species, whereas meso‐substitution induces pathway complexity due to competing hydrophobic and hydrogen bonding interactions. Our results show the importance of positional engineering for pathway control in aqueous self‐assembly.

The Characterization of Hydroxyl Terminated Epoxidized Natural Rubber (HTENR) via Oxidation Degradation Method

The degradation of epoxidized natural rubber (ENR-50) and liquid epoxidized natural rubber (LENR) was done via oxidative degradation method for the production of hydroxyl terminated epoxidized natural rubber (HTENR) and hydroxyl terminated liquid epoxidized natural rubber (HTLENR) has been analysed. Cobalt (II) acetylacetonate (CAA) were used as an oxidizing agent for chain scission reaction at temperature 60 °C in the presence of ethanol. The reaction temperature was fixed at 60 °C meanwhile reaction time and the amount of CAA were varied according to the reaction formulation. The HTENR and HTLENR obtained have been characterized using Gel Permeation Chromatography (GPC), Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR). GPC were used to determine the molecular weight before and after the oxidative degradation of respected HTENR and HTLENR were compared with ENR-50 and LENR. The lowest Mn and Mw of HTLENR that were obtained from the oxidative degradation method were found to be 5,163 g/mol and 58,087 g/mol. The appearances of OH end groups were verified by FTIR and NMR analyses to validate the position of each OH functional groups. FTIR analysis confirmed that HTENR and HTLENR contained OH group with the appearance of a broad peak around 3,400 cm-1 to 3,550 cm-1 after the reaction. The presence of OH end groups was verified by NMR analysis with the appearance at 3.39 ppm and 3.66 ppm, corresponding to methylene proton adjacent to hydroxyl group in HOCH2CH2CH2 and methane proton adjacent to OH group in CH2CH2CH(OH)CH3.

Various Cd(ii) coordination polymers induced by carboxylates: multi-functional detection of Fe3+, anions, aspartic acids and bovine serum albumin.

By adjusting carboxylates, six Cd(ii) coordination polymers based on a naphthalene-methylene mixed-bridged-amide ligand, [Cd(L)(DNBA)2] (1), [Cd2(L)2(BDC)2(H2O)2]·2H2O (2), [Cd(L)(1,4-CHDA)] (3), [Cd(L)(HIPA)(H2O)]·H2O (4), [Cd(L)(MIP)]·H2O (5), and [Cd(L)(PMA)0.5(H2O)]·H2O (6) [L = N,N'-bis(4-methylenepyridin-4-yl)-1,4-naphthalene dicarboxamide, HDNBA = 3,5-dinitrobenzoic acid, H2BDC = 1,4-benzenedicarboxylic acid, 1,4-H2CHDA = 1,4-cyclohexanedicarboxylic acid, H2HIPA = 5-hydroxyisophthalic acid, H2MIP = 5-methylisophthalic acid and H4PMA = pyromellitic acid] have been synthesized under hydrothermal conditions. 1 shows a 4-c sql coplanar structure. 2 exhibits a 2-fold vertical interpenetrating structure based on wave-like 4-c sql layers. 3 shows a (3,5)-c pnh network containing a unique μ3-L. 4 features a 4-c sql wave-like network. 5 and 6 exhibit 3D structures with 6-c pcu and 4-c mog topologies. The number of carboxyl groups and functional group positions of the carboxylates have an important influence on the structures of the title complexes. The fluorescent responses of 1-6 towards Fe3+, anions, aspartic acid and bovine serum albumin were investigated. Among them, 4 shows sensitivity and selectivity (KSV = 1.16 × 104 L mol-1 for Fe3+, 1.03 × 104 L mol-1 for CrO42-, 1.08 × 104 L mol-1 for Cr2O72-, 1.17 × 104 L mol-1 for MnO4- and 1.05 × 104 L mol-1 for aspartic acid).

Organic Solar Cells Based on Non-fullerene Small-Molecule Acceptors: Impact of Substituent Position

Summary Molecular engineering of non-fullerene small-molecule acceptors (SMAs) plays a key role in enhancing the performance of organic solar cells. An effective strategy is to introduce functional groups into SMA end groups to tune the electronic and morphological properties of polymer/SMA blends. Here, molecular dynamics simulations and long-range corrected density functional theory calculations are combined to examine the impact of the position of methoxy substitution in the SMA end groups. As representative systems, blends of the IT-OM small-molecule acceptor with the PBDB-T polymer donor are explored; three different positions of the methoxy substitution of the IT-OM end groups are examined. By considering intermolecular mixing and packing, the energetic distribution of the charge-transfer electronic states, the exciton-dissociation and non-radiative recombination processes, and the electron-transfer rates among adjacent acceptors, we provide a comprehensive molecular-scale rationalization of the significant experimental variations in device performance for PBDB-T/IT-OM-based solar cells as a function of methoxy position.

Corrosion Inhibition Mechanism and Efficiency Differentiation of Dihydroxybenzene Isomers Towards Aluminum Alloy 5754 in Alkaline Media.

The selection of efficient corrosion inhibitors requires detailed knowledge regarding the interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. The position of functional groups between different isomers is often overlooked, but is no less important, since factors like steric hinderance may significantly affect the adsorption mechanism. In this study, we have presented how different dihydroxybenzene isomers interact with aluminum alloy 5754 surface, reducing its corrosion rate in bicarbonate buffer (pH = 11). We show that the highest inhibition efficiency among tested compounds belongs to catechol at 10 mM concentration, although the differences were moderate. Utilization of novel impedance approach to adsorption isotherm determination made it possible to confirm that while resorcinol chemisorbs on aluminum surface, catechol and quinol follows the ligand exchange model of adsorption. Unlike catechol and quinol, the protection mechanism of resorcinol is bound to interaction with insoluble aluminum corrosion products layer and was only found efficient at concentration of 100 mM (98.7%). The aforementioned studies were confirmed with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. There is a significant increase in the corrosion resistance offered by catechol at 10 mM after 24 h exposure in electrolyte: from 63 to 98%, with only negligible changes in inhibitor efficiency observed for resorcinol at the same time. However, in the case of resorcinol a change in electrolyte color was observed. We have revealed that the differentiating factor is the keto-enol tautomerism. The Nuclear Magnetic Resonance (NMR) studies of resorcinol indicate the keto form in structure in presence of NaOH, while the chemical structure of catechol does not change significantly in alkaline environment.

Effect of Functional Chemistry on the Rejection of Low-Molecular Weight Neutral Organics through Reverse Osmosis Membranes for Potable Reuse

Potable reuse facilities must be designed and operated to minimize the presence of contaminants of emerging concern (CECs) and other trace organics in the product water. Reverse osmosis (RO) is incorporated into the process train of many potable reuse facilities and has been demonstrated to achieve excellent removal of many, but not all, organic compounds. Organics that may be poorly removed by RO include low-molecular weight (MW) neutral compounds. This laboratory study examined the rejection of 73 low-MW neutral organics through a commercial RO membrane that is commonly used in potable reuse applications. The organics were selected using a reductionist approach so that the effect of individual functional groups on rejection could be ascertained. The research demonstrated that halogens, carbonyl functional groups, C═C double bonds, and aromaticity decrease rejection, that methyl and hydroxyl functional groups increase rejection, and that the position of functional groups in structural isomers has a significant effect on rejection. The results help explain the discrepancies and inconsistencies in RO rejection of neutral organics that are observed when considered from the conventional perspective of molecular size and hydrophobicity.

Nanoscale chemical mapping of oxygen functional groups on graphene oxide using atomic force microscopy-coupled infrared spectroscopy

The unambiguous determination of the chemical functionality over graphene oxide (GO) is important to unleash its potential applications. However, the mapping of oxygen functionalities distribution remains to be unequivocally determined because of highly inhomogeneous non-stoichiometric structures and ultra-thin layers of GO. In this study, we report an experimental observation of the spatial distribution of oxygen functional groups on monolayer and multilayer GO using AFM-IR, atomic force microscopy coupled with infrared spectroscopy. Overcoming conventional IR diffraction limit for several micrometers, the novel AFM-IR reaches high spatial resolution ∼20 nm and could detect IR absorption on ∼1 nm thickness of monolayer GO. With nanoscale chemical mapping, the distribution of different oxygen functional groups is distinguished with AFM-IR over the GO surface. It allows us to observe that these oxygen functional groups prefer to sit on the fold areas, in discrete domains and on the edges of GO, which gave more insights into its chemical nature. The determination of the position of functional groups through precise imaging contributes to our understanding of GO structure-properties relations and paves the way for targeted tethering of polymers, biomaterials, and other nanostructures.

Functional group configuration influences salt transport in desalination membrane materials

Five methacrylate-based co-polymers, which have different ratios of 2-hydroxyethyl methacrylate (HEMA) and glycerol methacrylate (GMAOH) co-monomers, were prepared to investigate the influence of functional group configuration on salt transport properties. The HEMA and GMAOH co-monomers were selected because of the differences in position and number of hydroxyl groups in the two molecules. Co-polymer composition was varied systematically from a vicinal diol-rich (GMAOH-rich) configuration to a distributed hydroxyl group (HEMA-rich) configuration. To decouple the impact of functional group configuration and of changing water content on transport properties, all of the materials were prepared to have statistically equivalent water content. Salt sorption was lower and salt diffusion was slower in the HEMA-rich configuration compared to the GMAOH-rich configuration. Microwave dielectric relaxation spectroscopy revealed lower relative permittivity (i.e., dielectric constant) for the HEMA-rich co-polymers, which is consistent with suppressed salt sorption in those materials compared to the GMAOH-rich co-polymers. This observation was complemented by state of water analysis that suggested freezable (i.e., bulk-like) water content decreased as HEMA content increased. Both results suggest that stronger interactions between water molecules and the polymer are favored when hydrophilic functional groups are distributed more evenly throughout the material. These results suggest that functional group position in hydrated polymers influences salt transport properties, and engineering polymers that have a distributed functional group configuration may suppress salt transport properties, which could result in favorable materials for desalination membranes.

Multiwavelength Raman spectroscopy of ultranarrow nanoribbons made by solution-mediated bottom-up approach

Here we present a combined experimental and theoretical study of graphene nanoribbons (GNRs), where detailed multi-wavelength Raman measurements are integrated by accurate ab initio simulations. Our study covers several ultra-narrow GNRs, obtained by means of solution-based bottom-up synthetic approach, allowing to rationalize the effect of edge morphology, position and type of functional groups as well as the length on the GNR Raman spectrum. We show that the low-energy region, especially in presence of bulky functional groups is populated by several modes, and a single radial breathing-like mode cannot be identified. In the Raman optical region, we find that, except for the fully-brominated case, all GNRs functionalized at the edges with different side groups show a characteristic dispersion of the D peak (8-22 cm-1/eV). This has been attributed to the internal degrees of freedom of these functional groups, which act as dispersion-activating defects. The G peak shows small to negligible dispersion in most of the cases, with larger values only in presence of poor control of the edges functionalization, exceeding the values reported for highly defected graphene. In conclusion, we have shown that the characteristic dispersion of the G and D peaks offer further insight on the GNR structure and functionalization, by making Raman spectroscopy an important tool for the characterization of GNRs.

Polysubstituted Hexa-cata-hexabenzocoronenes: Syntheses, Characterization, and Their Potential as Semiconducting Materials in Transistor Applications.

A series of tetra- and octa-substituted hexa-cata-hexabenzocoronenes (cata-HBCs) were synthesized from tetraryl olefins via iodine- and iron chloride-catalyzed oxidative cyclodehydrogenation reactions. The substitutions on the periphery of the parent HBC serve to modify the photophysical properties, highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, and thermal stabilities of the respective derivatives. The crystal structures were determined to display multiple twists in the framework, resulting in different packing motifs depending on the position, type, and number of functional groups on the hexabenzocoronene framework. Nearly perfect co-facial packing to marginally or extensively shifted co-facial stacks were obtained due to substitution. The single crystals of parent HBC were used to fabricate single-crystal field-effect transistors, from which the highest p-channel mobility of 0.51 cm2 V-1 s-1 was measured. Thin-film transistors of selected HBCs were also prepared, and 0.61 cm2 V-1 s-1 was obtained for MeHBC-2. These results attest the potential of these materials as semiconducting materials.