Amine Hydrogen Research Articles

Linker engineering of benzothiadiazole and its derivative-based covalent organic frameworks for efficient photocatalytic oxidative amine coupling and hydrogen peroxide generation

Benzothiadiazole and its derivative-based COFs were prepared, in which benzothiadiazole-based COF exhibits superior photocatalytic aerobic oxidation of amine coupling, while the naphthothiadiazole-based COF shows the highest H2O2 production rate.

SYNTHESIS, CHARACTERIZATION, AND ANTIMICROBIAL EVALUATION OF IMINE-LINKED BENZOTHIAZINE COMPOUNDS BY ULTRASOUND METHOD

This work seeks to evaluate the antibacterial properties of the compounds and create imine-linked benzothiazine derivatives using a novel, eco-friendly ultrasonic technique. Escherichia coli and Staphylococcus aureus were utilized to assess the synthetic compounds, SBIa-e, for their antibacterial activity. All compounds were soluble in organic solvents but insoluble in water, with yields ranging from 68 to 77%. The molecules showed stretching vibrations corresponding to various functional groups. The presence of amine hydrogen (2.0, 7.0 ppm), aliphatic protons (2.6- 4.3 ppm), imine hydrogen (8.0-8.5 ppm), and protons of the aromatic ring (6.8-7.9 ppm) was indicated by the 1HNMR spectra. Both the bacterial strains were all susceptible to the antibacterial action of the compounds, which showed dose-dependent effects. When the compounds were compared to gram-positive bacteria, it was discovered that the former had greater effectiveness than the latter. SBId had the lowest IC50 against Staphylococcus aureus (70.16 µg/mL) and Escherichia coli (49.19 µg/mL) among the drugs whose IC50 values were calculated.

Dual‐Stimuli Cooperative Responsive Hydrogel Microactuators Via Two‐Photon Lithography

With the development of bionics as well as materials science, intelligent soft actuators have shown promising applications in many fields such as soft robotics, sensing, and remote manipulation. Microfabrication technologies have enabled the reduction of the size of responsive soft actuators to the micron level. However, it is still challenging to construct microscale actuators capable of responding to different external stimuli in complex and diverse conditions. Here, this work demonstrates a dual-stimuli cooperative responsive hydrogel microactuator by asymmetric fabrication via femtosecond laser direct writing. The dual response of the hydrogel microstructure is achieved by employing responsive hydrogel with functional monomer 2-(dimethylamino)ethyl methacrylate. Raman spectra of the hydrogel microstructures suggest that the pH and temperature response of the hydrogel is generated by the changes in tertiary amine groups and hydrogen bonds, respectively. The asymmetric hydrogel microstructures show opposite bending direction when being heated to high temperature or exposed to acid solution, and can independently accomplish the grasp of polystyrene microspheres. Moreover, this work depicts the cooperative response of the hydrogel microactuator to pH and temperature at the same time. The dual-stimuli cooperative responsive hydrogel microactuators will provide a strategy for designing and fabricating controllable microscale actuators with promising applications in microrobotics and microfluidics.

1-Methyl-5-nitro-imidazolium chloride.

The title salt, C4H6N3O2 +·Cl-, exhibits multiple hydrogen-bonding inter-actions involving the nitro-imidazolium cation and the chloride anion. Strong hydrogen bonds between the amine hydrogen atom and the chloride anion link the ionic moieties. Of note, with respect to H⋯Cl inter-actions, the central aromatic hydrogen atom displays a shorter inter-action than the other aromatic hydrogen atom. Finally, inter-actions are observed between the nitro moiety and methyl H atoms. While no π-π stacking is observed, anion-π inter-actions are present. The crystal was refined as a two-component twin.

Functional miscibility and thermomechanical properties enhancement of substituted phthalic acetylated modified chitin filler in biopolymer composite.

The miscibility between hydrophobic and hydrophilic biopolymers has been of significant challenge. This study used a novel simplified chitin modification method to produce phthalic chitin using phthalic anhydride in a substitution reaction. The FT-IR functional group analysis was used to confirm the substitution reaction. The modified chitin was used as compatibilizer in polylactic acid (PLA)/starch biocomposite to enhance its properties. The biocomposite was prepared using melt extrusion and compression moulding technique. The biocomposite's morphological, thermomechanical and water absorption properties were characterized using scanning electron microscope, tensile test, dynamic mechanical analysis, thermogravimetry analysis, differential scanning calorimetry, thickness swelling and water absorption test. The FT-IR study shows a successful substitution reaction of the amine hydrogen ion present in the chitin as opposed to substituting the hydrogen ion in the hydroxide group. The tensile and impact properties of biocomposite incorporated with modified chitin showed better results compared with other samples. The SEM images showed uniform miscibility of the modified biocomposite. The dynamic mechanical analysis showed improved modulus value with the incorporation of modified chitin. The thermal properties showed improved thermal stability of the modified biocomposite. Furthermore, the percentage of water absorbed by biocomposite with modified chitin is reduced compared with the PLA/starch biocomposite. The produced biodegradable ternary blend can be used as a substitute for plastics in industrial applications.

Boron Modified Cu/Al2O3 Catalysts for the Selective Reductive Amination of Levulinic Acid to N‐Substituted Pyrrolidinones

AbstractThe reductive amination of biomass‐derived levulinic acid (LA) to value‐added N‐substituted pyrrolidinones with amine and molecular hydrogen over heterogeneous catalyst represents an atom‐economical and scalable route. In this paper, a series of boron doped Cu/Al2O3 catalysts via kneading and impregnation method are developed for the continuous reductive amination of LA. Compared with Cu/Al2O3, Cu10/AlB3O catalyst exhibits greatly improved catalytic performance for this reaction at low operation temperature. Structure‐property correlation investigations were performed with diverse characterization methods, and the results revealed that the excellent catalytic performance of boron doped Cu/Al2O3 catalysts was mainly attributed to the synergistic effect of its well‐dispersed Cu nanoparticles, appropriate surface Cu electronic state and surface acidic sites nearby. Besides, Cu10/AlB3O shows great stability during the reaction over 200 h. This work provides a low‐cost, efficient and environmentally friendly heterogeneous catalytic system for the continuous production of N‐substituted pyrrolidinones.

Design and Synthesis Ligands Tetradents Substituted with Halogenes in α- Position and Conjugation with Riboflavin (Bioconjugates) Conjugate ligands Type TPA’s with Flavonoids as un Electron Mediator

In this article, we describe the process of binding riboflavin to a simple tetradents ligand substituted in α- position from TPAs types, by reacting bromotetraacetate riboflavin with α- substituted TPA with one of the pyridine rings by nitrile group and the two other pyridine rings by halogen atoms. This type of ligands showed very important properties for the activation and transfer of oxygen to a substrate in presence of iron salt. After the tetradents were obtained, the nitrile group was reduced to an amine group where it reacts with Boc group to protect one of the amine hydrogen and then bound to the bromotetraacetate through the amine group under special reactive conditions, to form the α-8-TPAs N- Ac4riboflavin ligands. This compound can be described as a molecular tweezers in which the flavin moiety acts as a potential electron mediator.

Trans-Bis(4-amino-pyridine-κN)bis-(quin-ox-aline-2,3-di-thiol-ato-κ2 S,S')platinum(IV) dimethyl sulfoxide monosolvate.

In the structure of the title solvated complex, [Pt(C8H4N2S2)2(C5H6N2)2]·C2H6OS or trans-[Pt(4-ap)2(qdt)2]·dmso (4-ap = 4-amino-pyridyl, C5H6N2; qdt = quinoxaline-2,3-di-thiol-ate, C8H4N2S2; dmso = dimethyl sulfoxide, C2H6OS) the centrosymmetric complex exhibits Pt-S distances in agreement with other PtIV-S bond lengths found in platinum(IV) di-thiol-ene complexes. The qdt ligands have inter-molecular inter-actions with an amine hydrogen atom on a 4-ap ligand (hydrogen bonding) and have sandwich π-π inter-actions with a neighboring qdt ligand.

Effects of Protonation State on Electrocatalytic CO2 Reduction by a Cobalt Aminopyridine Macrocyclic Complex.

A critical component in the reduction of CO2 to CO and H2O is the delivery of 2 equiv of protons and electrons to the CO2 molecule. The timing and sequencing of these proton and electron transfer steps are essential factors in directing the activity and selectivity for catalytic CO2 reduction. In previous studies, we have reported a series of macrocyclic aminopyridine cobalt complexes capable of reducing CO2 to CO with high faradaic efficiencies. Kinetic investigations reveal a relationship between the observed rate constant (kobs) and the number of pendant amine hydrogen bond donors minus one, suggesting the presence of a deprotonated active catalytic state. Herein, we investigate the feasibility of these proposed deprotonated complexes toward CO2 reduction. Two deprotonated derivatives, Co(L4-) and Co(L2-), of the tetraamino macrocycle Co(L) were independently synthesized and structurally characterized revealing extensive delocalization of the negative charge upon deprotonation. 1H nuclear magnetic resonance spectroscopy and ultraviolet-visible titration studies confirm that under catalytic conditions, the active form of the catalyst gradually becomes deprotonated, supporting thus the ndonor - 1 relationship with kobs. Electrochemical studies of Co(L4-) reveal that this deprotonated analogue is competent for electrocatalysis upon addition of an exogenous weak acid source, such as 2,2,2-trifluoroethanol, resulting in faradaic efficiencies for CO2-to-CO conversion identical to those observed with the fully protonated derivative (>98%).

The Amine Group as Halogen Bond Acceptor in Cocrystals of Aromatic Diamines and Perfluorinated Iodobenzenes

In order to study the proclivity of primary amine groups to act as halogen bond acceptors, three aromatic diamines (p-phenylenediamine (pphda), benzidine (bnzd) and o-tolidine (otol)) were cocrystallised with three perfluorinated iodobenzenes (1,4-tetrafluorodiiodobenzene (14tfib), 1,3-tetrafluorodiiodobenzene (13tfib) and 1,3,5-trifluorotriiodobenzene (135tfib)) as halogen bond donors. Five cocrystals were obtained: (pphda)(14tfib), (bnzd)(13tfib)2, (bnzd)(135tfib)4, (otol)(14tfib) and (otol)(135tfib)2. In spite of the variability of both stoichiometries and structures of the cocrystals, in all the prepared cocrystals the amine groups form exclusively I···N halogen bonds, while the amine hydrogen atoms participate mostly in N–H⋯F contacts. The preference of the amine nitrogen atom toward the halogen bond, as opposed to the hydrogen bond (with amine as a donor), is rationalised by means of computed hydrogen and halogen bond energies, indicating that the halogen bond energy between a simple primary amine (methylamine) and a perfluorinated iodobenzene (pentafluoroiodobenze ne) is ca. 15 kJ mol−1 higher than the energy of the (H)NH∙∙∙NH2 hydrogen bond between two amine molecules.

Crystal structure of pomalidomide Form I, C13H11N3O4

The crystal structure of pomalidomide Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Pomalidomide Form I crystallizes in the space group P-1 (#2) with a = 7.04742(9), b = 7.89103(27), c = 11.3106(6) Å, α = 73.2499(13), β = 80.9198(9), γ = 88.5969(6)°, V = 594.618(8) Å3, and Z = 2. The crystal structure is characterized by the parallel stacking of planes parallel to the bc-plane. Hydrogen bonds link the molecules into double layers also parallel to the bc-plane. Each of the amine hydrogen atoms acts as a donor to a carbonyl group in an N–H⋯O hydrogen bond, but only two of the four carbonyl groups act as acceptors in such hydrogen bonds. Other carbonyl groups participate in C–H⋯O hydrogen bonds. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Regulation of stomatal aperture in response to drought stress mediating with polyamines, nitric oxide synthase and hydrogen peroxide in Rosa canina L.

ABSTRACT To assess the role of genes involved in polyamines synthesis, nitric oxide synthase (NOS), copper amine oxidase activity (CuAO) and hydrogen peroxide (H2O2) in regulation of stomatal aperture to drought stress in Rosa canina L., a study was performed at three irrigating levels (25%, 50%, and 100% field capacity) with three replications at 1, 3, 6 and 12 days. The results showed that putrescine (Put) accumulation occurred under both 50% and 25% FC at 1 d. Furthermore, the role of the Put direct biosynthesis pathway ornithine decarboxylase (ODC) was more effective under 50% FC whereas in the 25% FC the Put indirect production pathway (agmatine iminohydrolase (AIH), N-carbamoyl putrescine amidohydrolase (CPA) and arginine decarboxylase (ADC)) was more effective. HPLC results showed that the accumulation of spermidine (Spd) and spermine (Spm) is consistent with the expression of S-adenosyl methionine decarboxylase (SAMDC), spermidine synthase (SPDS) and spermine synthase (SPMS) genes. Spd accumulation under both 50% and 25% FC occurred on the 3 d and then decreased in the other days. Spm content showed an increasing trend from 6 d under 50% FC and from 3 d under 25% FC. Our results suggest that among the measured polyamines, Put oxidation through CuAO activity increased resulted in an increase in H2O2 production. The H2O2 accumulation also as a secondary messenger led to enhance in NOS gene expression. Increase in NOS gene expression can act as a signal resulting in stomatal closure.

Zirconium‐Salan Catalyzed Enantioselective α‐Hydroxylation of β‐Keto Esters

AbstractWe report herein the development of enantioselective and scalable α‐hydroxylation of 1‐indanone‐derived β‐keto esters by Zr(IV) complexes bearing readily available C2‐symmetric salan ligands and cumene hydroperoxide as an oxidant, affording synthetically valuable hydroxylation products in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee) under mild reaction conditions. In mechanistic studies, we have shown that (1) a Zr(IV)‐salan complex was generated in situ as the active catalyst responsible for the chiral induction, (2) the transfer of the electrophilic fragment from cumene hydroperoxide to the Zr(IV)‐bound enolate was accompanied by a heterolytic O−O bond cleavage, and (3) the formation of hydrogen bond between the amine hydrogen atom(s) of the salan ligand and the hydroxy group of cumene hydroperoxide was significant for stabilizing the stereocontrolled transition state and improving the enantioselectivity.magnified image

Facile synthesis of a versatile Ti/Ti-W@PANI nanocomposite for sustainable hydrogen production under solar irradiation

TiO2/TiO2-WO3 (Ti/Ti-W) reinforced PANI hybrid composite synthesis and investigation of its structural and photocatalytic hydrogen evolution activity are discussed in the present work. The efficiency of the synthesized core/shell structured Ti/Ti-W in re-enforcing polyaniline, a conductive polymer with low band gap and enhanced visible light response for hydrogen evolution reaction is studied. Polyaniline supported mixed oxide composite is successfully fabricated by an in-situ polymerization reaction in presence of the as prepared composite. The interaction at the interface of the polymer and the oxide nanofiller in the resultant composite makes it a better visible light harvestor with significantly enhanced charge separation. The modified PANI/Ti/Ti-W composite yields 20.1 mL of hydrogen from 20 mL water containing 0. 1 g of diethyl amine hydrogen chloride with a quantum efficiency of 20.7%. The improved hydrogen delivering capacity offered by the polymer composite could be better explained in terms of effective utilization of solar energy, surface porosity and efficient separation of charge carriers. The mesoporous catalyst facilitated photocatalytic reaction by rapid diffusion, adsorption of reactants and by fast desorption of product molecules. The composite takes the advantage of both the organic and the inorganic components to achieve active hydrogen generation.

Thin epoxy layers on native aluminium oxide: Specific ageing processes in mild conditions

Post-cured epoxy layers (EP, approx. 100 nm and 1 µm) of three amine hydrogen – oxirane ratios are prepared in dried air on natively oxidised aluminium substrate. A less crosslinked interphase forms as the consequence of adhesive interactions. Even though the layers exhibit very good durability in moist-warm air for up to 100 d, two stages of chemical ageing are revealed. During a short initial stage, some water absorbs firmly in the EP networks. Residual oxirane rings and secondary amine groups are shown to hydrolyse, while network chains remain intact. Marking the 2nd stage, dedicated autoxidation reactions are proven to simultaneously attack tertiary amine crosslinks and α-CH2 groups at phenylene ether units. These reactions destroy network chains, and the release of network fragments was established. Moreover, network destruction proceeds more effectively in 100 nm layers as the surface erodes slightly, even under the given environmentally mild conditions. That observation proves a specifically reduced durability for the interphase at the contact with native aluminium oxide.

First-principle studies on the gas phase OH-initiated oxidation of O-toluidine

In the present work, the gas phase reaction of OH radical initiated O-toluidine (OTOD) oxidation is investigated at ROCBS-QB3. Different pathways for OH radical additions to the benzene ring sites and H-atom abstractions are explored in details. At 200 K, the oxidation mechanism of OTOD is thoroughly dominated by the OH-addition to the aromatic ring, whereas the main favorable route is the OH addition to C2 atom with a branching ratio of 52.76%. Raising temperature to 1000 K, the total abstraction of amine's hydrogens becomes the main oxidation pathway for OTOD with contributions of 29.29%. The atmospheric lifetimes of aniline and OTOD are calculated to be 20.74 and 11.23 min., respectively. The fate of OTOD-OH2 (P2) adduct with atmospheric O2 molecule is inspected using the unimolecular Rice-Ramsperger-Kassel-Marcus (RRKM-ME) to verify our results at transition state theory (TST) and shows pressure and temperature dependence of the secondary oxidation mechanism.

Betaine-based deep eutectic solvents with diol, acid and amine hydrogen bond donors for carbon dioxide absorption

Deep eutectic solvents (DESs) are known as alternative green solvents due to their ease of synthesis, availability, biodegradability and negligible volatility. DESs consisted of betaine as the hydrogen bond acceptor with 1,2-propanediol, levulinic acid and methyl diethanolamine (MDEA) as the hydrogen bond donors, were prepared in 1:3 and 1:6 molar ratios. The carbon dioxide solubilities in these DESs were determined using a volumetric apparatus at 313.15 K and 6 bar. The results show that CO2 solubilities in betaine-based DESs are higher than the reported CO2 solubilities in choline chloride-based DESs, for DESs having the same hydrogen bonding donor and an identical or similar composition. The viscosity and polarity of hydrogen bond donors affected the ability of deep eutectic solvent to absorb carbon dioxide. The betaine-MDEA deep eutectic solvent, with molar ratio of 1:6, has the highest absorption capacity of 0.0814 mol CO2/mol DES, measured at 313.15 K and 6 bar.

Anticancer activities of novel Mannich bases against prostate cancer cells

This study was designed to synthesize hybridizing molecules starting from compound of 6-(4-phenyl-piperazin-1-yl)pyridine-3-ylamine by enhancing its biological activity with other heterocycles and to determine anticancer activity of the resulting compounds. To this end, 6-(4-phenylpiperazin-1-yl)pyridin-3-ylamine (4) was used as the leading compound, which is known to exert anticancer activities. The synthesis of the leading compound was carried out using 1-(5-nitropyridin-2-yl)-4-phenylpiperazine (3) which was obtained by a novel method with the reaction of N-phenylpiperazine (2) and 2-chloro-5-nitropyridine. 6-(4-phenylpiperazin-1-yl)pyridin-3-ylamine (4) was converted to compound 5, an active intermediate compound, by substitution of one of the amine hydrogens with ethyl bromoacetate. The resulting ester product (5) followed by the hydrazidation (6) was added arylisocyanate to obtain the active intermediate (8). Then, by a series of substitution through cyclization and condensation reactions, thiazolidinone (9), 1,3,4-oxadiazole (7), and 1,2,4-triazole (10) were synthesized. Novel Mannich bases (11a–11f and 12a–12f) were obtained using oxazole (7) and triazole (10) hetero rings with primer or secondary amine compounds. The characterization of the compounds was completed using FT IR, 1H-NMR, 13C-NMR, HRMS spectroscopic methods and elemental analysis technique. The chemicals, then, were tested for their anticancer activities against prostate cancer cell lines PC3 [ATCC, CRL-1435], LNCaP [ATCC, CRL-1740], and DU145 [ATCC, HTB-81]. The results revealed that the Mannich bases exhibited moderate cytotoxic activity against cancer cells tested.

"Switch on" fluorescent sensor for the detection of fluoride ions in solution and commercial tooth paste.

A simple and novel uracil based chemosensor (1) has been developed by one step reaction, which selectively detected F- ions via "switch on" fluorescence mode. Upon the addition of F- ion to CH3CN solution of 1, the non-fluorescent probe became highly fluorescent, showing a color change from colorless to fluorescent blue, when irradiated with 280nm light. 1H NMR studies revealed the binding sites of chemosensor 1, where C-5 hydrogen and amine hydrogens formed hydrogen bonding with F- ion. This binding mode was further confirmed using DFT calculations. Significantly, the detection limit of chemosensor 1 towards F- has been evaluated to be 47.6nM, which is lower than the maximum values of F- (1.5mg/L) ions permitted by WHO. The in-situ generated 1-F- complex has been used for secondary sensing of Ca(NO3)2, one of the component of the fertilizer. Moreover, the sensor has been successfully applied for detection of fluoride ion in commercial tooth paste.

Nuclear Motion in the Intramolecular Dihydrogen-Bound Regime of an Aminoborane Complex.

The 1,3-diaza-2,4-diborobutane (NBNB) molecule serves as the smallest model complex of an intramolecular "dihydrogen bond," which involves a nominally hydrogen-bonding interaction between amine and borane hydrogen atoms. In the present study, the role of this dihydrogen bond in influencing the inherent molecular dynamics of NBNB is investigated computationally with ab initio molecular dynamics and path integral molecular dynamics techniques, as well as vibrational spectra analysis and static quantum chemistry computations. These simulations indicate that the dihydrogen-bonding interaction impacts both the high- and low-frequency motions of the molecule, with the dominant motions involving low-frequency backbone isomerization and terminal amine rotation. Geometric isotope effects were found to be modest. The analysis also addresses the paradoxical fostering of amine rotation via a relatively strong dihydrogen bond interaction. Electrostatic and geometric factors most directly explain this effect, and although some orbital evidence was found for a small covalent component of this interaction, the dynamics and electronic structure suggest that electrostatic contributions are the controlling factors for molecular motion in NBNB.