Aniline Group Research Articles

Studies on Associated Solutions: Thermodynamic Parameters of Binary Liquid Mixtures of Propiophenone and o-Substituted Anilines

The densities (ρ), speeds of sound (u), and viscosities (η) are reported for binary mixtures of propiophenone with ortho-substituted aniline (2-chloroaniline, 2-methylaniline, and 2-methoxyaniline) over the entire composition range from 303.15 to 318.15 K and at atmospheric pressure 0.1 MPa. The excess/deviation functions (VE, $$k_{s}^{E}$$ , and Δη) are calculated from the measured densities, speeds of sound and viscosities at experimental temperatures. The excess properties have been analyzed through molecular interactions. The FT-IR data indicate that the formation of intermolecular hydrogen bonding (N–H⋅⋅⋅O–H) between hydrogen atom of amine group of o-substituted aniline and oxygen atom of carbonyl of propiophenone in the binary liquid mixtures.

Electro- and Photochemical Reduction of CO2 by Molecular Manganese Catalysts: Exploring the Positional Effect of Second-Sphere Hydrogen-Bond Donors.

A series of molecular Mn catalysts featuring aniline groups in the second-coordination sphere has been developed for electrochemical and photochemical CO2 reduction. The arylamine moieties were installed at the 6 position of 2,2'-bipyridine (bpy) to generate a family of isomers in which the primary amine is located at the ortho- (1-Mn), meta- (2-Mn), or para-site (3-Mn) of the aniline ring. The proximity of the second-sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst 1-Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9-fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)3 Br (901 vs. 102 s-1 , respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration-dependent shift in product selectivity from CO (at high [catalyst]) to HCO2 H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.

Synthesis and antiproliferative evaluation of novel 8-cyclopentyl-7,8-dihydropteridin-6(5H)-one derivatives as potential anticancer agents

Based on our previous work, a novel class of 8-cyclopentyl-7,8-dihydropteridin-6(5H)-one derivatives were synthesized and evaluated as antiproliferative agents. Structure-activity relationship analysis revealed that the greatest activities were achieved with a 4-(4-methylpiperazin-1-yl)aniline group at C-2 position of dihydropteridin-6(5H)-one core, and the most promising compound 6k demonstrated comparable antiproliferative activity with Palbociclib and more potent than our parent derivative 4 toward four cell lines including HCT-116, HeLa, HT-29, and MDA-MB-231 with IC50 values of 3.29, 6.75, 7.56, and 10.30 μM, respectively. Moreover, the mechanism studies revealed that compound 6k could induce cell cycle arrest at G2/M phase via a concentration-dependent manner. In general, these preliminary observations suggested that these compounds could serve as promising scaffolds for further modification to develop novel and highly potent cancer therapy agents.

Kinetics and pathways of the degradation of PPCPs by carbonate radicals in advanced oxidation processes

The carbonate radical (CO3•−) is a typical secondary radical observed in engineering and natural aquatic systems. This study investigated the degradation kinetics of 20 pharmaceuticals and personal care products (PPCPs) by CO3•− and the transformation pathways of a typical PPCP (naproxen) that is susceptible to CO3•−. CO3•− is highly selective for compounds containing aniline and phenolic hydroxyl groups as well as naphthalene rings, such as sulfamethoxazole, sulfamethazine, salbutamol, propranolol, naproxen, and macrolide antibiotics such as azithromycin, for which the second-order rate constants range from 5.6 × 107 M−1s−1 to 2.96 × 108 M−1s−1. A good linear relationship is observed between the natural logarithms of kCO3•− and the negative values of the Hammett Σσp+ constant for aromatic PPCPs, indicating that electron-donating groups promote the attack of benzene derivatives by CO3•−. The contribution of CO3•− to naproxen degradation is significant in different processes such as UV/H2O2, UV/persulfate, UV/chlorine, and UV/monochloramine, in the presence of HCO3−, which compensates for the decreased contributions of primary radicals. In particular, the formation of CO3•− increases the first-order rate constant of naproxen by 127% in UV/monochloramine in the presence of 50 mM HCO3− compared to that without HCO3−. Natural organic matter (NOM) exerts a slight scavenging effect on CO3•−, decreasing the inhibition effect of NOM on the degradation of naproxen by UV/H2O2 in the presence of HCO3−. The pathways involved in the transformation of naproxen by CO3•− include decarboxylation, hydroxylation, ketonization, demethylation and aldolization. In addition, the alteration of the genotoxicity during naproxen degradation by CO3•− was negligible.

INFLUENCE OF SUBSTITUTES ON THE RATE OF THE REACTION OF META- АND PARASUBSTITUTED BENZOIC ACIDS WTH ANILINE, CATALYZED BY POLYBUTOXYTITANATES

The polybutoxytitanates catalysis of acylation of anilines by meta- and parasubstituted benzoic acid results in substituted benzanilides. The rate constants of this second-order reaction (the first in terms of aniline and substituted benzoic acid; boiling ortho-xylene, 145 °С) correlates well according to the Hammett equation with two straight lines for individual groups of substituents with ρ = 1.76 (electron donors) and 0.12 (electron acceptors). Oxybenzoic and phthalic acids, that do not react with aniline and inhibit the interaction of the latter with benzoic acid, fall out of this dependence. Based on these data, as well as the results of a previous studies of the interaction of substituted anilines with a benzoic acid made under comparable conditions, a mechanism of bifunctional catalysis due to the formation of titanium polybutoxybenzoates in the first minutes of the reaction in situ — the true catalysts of the process, is proposed. The nucleophilic center of the catalyst can be represented by the carbonyl group of a substituted benzoate bound to a titanium atom, forming an H-bond with hydrogen atoms of the amino group of aniline, thus activated to react with a substituted benzoic acid. The titanium atoms of polytitanate (coordination catalysis) and their complexes with the resulting substituted benzanilides (acid catalysis) can act as the electrophilic center of a catalyst that activates the carbonyl group of a substituted benzoic acid to nucleophilic attack by aniline. A titanium atom bound to a substituted benzoate exhibits, depending on the nature of the substituent, various catalytic activity.

Acid-Base Interaction Enhancing Oxygen Tolerance in Electrocatalytic Carbon Dioxide Reduction.

Hybrid electrodes with improved O2 tolerance and capability of CO2 conversion into liquid products in the presence of O2 are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO2 molecule and the basic amino group of aniline renders enhanced CO2 separation from O2 . Loaded with a cobalt phthalocyanine-based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O2 in the CO2 feed gas. The electrode can still produce CO at an O2 /CO2 ratio as high as 9:1. Switching to a Sn-based catalyst, for the first time O2 -tolerant CO2 electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm-2 in the presence of 5 % O2 .

Acid–Base Interaction Enhancing Oxygen Tolerance in Electrocatalytic Carbon Dioxide Reduction

AbstractHybrid electrodes with improved O2 tolerance and capability of CO2 conversion into liquid products in the presence of O2 are presented. Aniline molecules are introduced into the pore structure of a polymer of intrinsic microporosity to expand its gas separation functionality beyond pure physical sieving. The chemical interaction between the acidic CO2 molecule and the basic amino group of aniline renders enhanced CO2 separation from O2. Loaded with a cobalt phthalocyanine‐based cathode catalyst, the hybrid electrode achieves a CO Faradaic efficiency of 71 % with 10 % O2 in the CO2 feed gas. The electrode can still produce CO at an O2/CO2 ratio as high as 9:1. Switching to a Sn‐based catalyst, for the first time O2‐tolerant CO2 electroreduction to liquid products is realized, generating formate with nearly 100 % selectivity and a current density of 56.7 mA cm−2 in the presence of 5 % O2.

Harnessing aromaticity and intramolecular hydrogen bonding to tailor organosuperbases by using 2,4,6-cycloheptatriene-1-imine scaffold

The density functional theory (DFT) calculations at B3LYP/6-31 + G(d,p) level were performed for a series of new 2,4,6-cycloheptatriene-1-imine scaffolds which have potential to introduce as organosuperbases. In the present study, we have exploited the 2,4,6-cycloheptatriene-1-imines which strategically substituted at 2 and 7 positions by two potential anchoring arms having lone pair possessing atoms. The designed organic superbases were found to have the higher basicity than the benchmarked molecule, 1,8-bis(dimethylamino)-naphthalene. The proposed superbase B14 bearing guanidine and aniline groups possesses the highest proton affinity value as 1143.8 kJ mol−1. The protonation enthalpy, Gibbs free energy, harmonic oscillator model of aromaticity (HOMA), and nucleus-independent chemical shift (NICS) were used for the basicity comparison. After the protonation of the designed molecules, the positive charge on the conjugate acid is expected to be delocalized in the cycloheptatriene ring and led to its aromatization. The results indicate that the HOMA and NICS values of the ring in the conjugate acid are strongly elevated. On the other hand, very strong intramolecular hydrogen bonding is formed after protonation. These two factors enhance the stability of the conjugate acids and thereby increase the basicity of the designed molecules.

Oxidation effect of graft polysilane on fluorescence properties

Abstract Tritium is radioactive hydrogen isotope which can be easily absorbed by organisms. The release of tritium is harmful to human health and environment. For monitor tritium directly, the development of new scintillator with low excitation energy, high scintillation efficiency and enhanced oxidative resistance, is desired. Polysilane has unique fluorescence characteristics for the σ conjugate structure which allow the excited electrons delocalizing in the whole Si-Si main chain. Polysilane modified by functional side groups would be used as novel tritium-releasing scintillation if it had enough oxidative resistance. In this paper, preliminary study about modified polymethylsilane (PMS) is carried out on the relationship between oxidative resistance and fluorescence properties. The mechanism of oxidation which causes the fluorescence degradation is also discussed. Polymethylsilane grafting aniline groups (PA-PMS) preforms the most prominent fluorescence for the smaller electronegativity of N, but it shows a poor oxidative stability in the air. Its fluorescence properties decline significantly after being placed for a period of time, which is related to the oxidation of the amino group. By contrast, O bridging σ-n-π structure could acceptably provide both fluorescence properties and oxidative resistance at the same time, which are the pressing needs for the scintillator material in tritium monitor.

Vibrational Spectroscopic Analyses of (en)2-Td-type Clathrates

The clathrates of Hofmann-(en)2-Td-type, M(en)2M’(CN)4.Aniline (M=Cu,Cd; M’=Cd,Zn) and their hosts were synthesized with the confirmation using FTIR spectra. Hydrogen bonding interaction between π-cloud of phenyl ring of the guest molecule and ethylenediamine(en) of the host lattices was deduced from the upward shift in ν(CH)out of plane bending mode of aniline. A second type of hydrogen bonding between C≡N group of the host lattice and NH2 of aniline guest was also inferred from the downward shift in ν(C≡N) of the clathrates. The relative strength of H-bonding in the clathrates was found to be Hofmann-(en)2-Type > Hofmann-(en)2-Td-Phenol > Hofmann-(en)2-Td-Aniline. The presence of major peaks corresponding to various modes of guest aniline, ligand en and cyanide group in FT Raman spectra also confirms the formation of clathrates. Attempts to synthesize Ni(en)2M’(CN)4.Aniline (M’=Cd,Zn) resulted in the formation of M’(en)2Ni(CN)4.2Aniline (M’=Cd,Zn) due to the exchange of metal ions and greater stability of Ni(CN)4 unit.

New quinacridone derivatives: Synthesis, photophysical and third-order nonlinear optical properties

A series of quinacridone third-order nonlinear optical chromophores containing phenyl, 4-methoxyphenyl and N,N-bis(4-methoxyphenyl)aniline groups were designed and synthesized. The optical properties, electrical properties, theoretical calculations and Z-Scan of the compounds were measured and analyzed to investigate the relationship between structure and third-order NLO properties. The experimental results showed that the introduction of electron-donating groups at the N-position of quinacridone decreases the energy gap (Egap) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecule, and promotes intramolecular charge transfer (ICT). Quinacridone derivatives containing N, N-bis (4-methoxyphenyl) aniline have good third-order nonlinear optical properties, with the nonlinear absorption coefficient (β) value of 1.4319 × 10−13 and the second-order superpolarizability (γ) of 2.6849 × 10−33 esu.

Synthesis of a Novel Library of 1-Substituted Pyrido[1,2-a]benzimidazoles

The reactivity and synthesis of new analogues of pyrido[1,2-a]benzimidazoles have been explored. Twenty-three derivatives bearing phenoxy, thiophenoxy, aniline, and aryl groups at the 1-position were successfully synthesised in 25–91% yield, via nucleophilic substitution, Buchwald–Hartwig amination, and Suzuki coupling type processes. Solvent free synthetic protocols were employed to achieve the nucleophilic substitution of anilines with electron donating groups or moderately electron withdrawing groups on a sterically demanding intermediate (7a). An unusual polycyclic heterocycle was identified as a side-product during this work: a dimeric bis(pyrido[1,2-a]benzimidazole).

Barbituric Acid Based Fluorogens: Synthesis, Aggregation-Induced Emission, and Protein Fibril Detection.

Fluorescent dyes, especially those emitting in the long wavelength region, are excellent candidates in the area of bioassay and bioimaging. In this work, we report a series of simple organic fluorescent dyes consisting of electron-donating aniline groups and electron-withdrawing barbituric acid groups. These dyes are very easy to construct while emitting strongly in the red region in their solid state. The photophysical properties of these dyes, such as solvatochromism and aggregation-induced emission, are systematically characterized. Afterward, the structure–property relationships of these barbituric acid based fluorogens are discussed. Finally, we demonstrate their potential applications for protein amyloid fibril detection.

CF3 -Pyridinyl Substitution on Antimalarial Therapeutics: Probing Differential Ligand Binding and Dynamical Inhibitory Effects of a Novel Triazolopyrimidine-Based Inhibitor on Plasmodium falciparum Dihydroorotate Dehydrogenase.

The quest for reliable dihydroorotate dehydrogenase (DHODH) inhibitors has engendered the discovery of potential therapeutic compounds at different stages of clinical trials. Although promising, high attrition rates and unfavorable bioactivities have limited their drug developmental progress. A recent structural modification of DSM265, a triazolopyrimidine-based inhibitor, yielded DSM421, derived by the substitution of the SF5 -aniline group on DSM265 with a CF3 -pyridinyl moiety. Consequently, DSM421 exhibited improved pharmacological and pharmacokinetics attributes relative to DSM265. The improved bioactivity mediated by the CF3 -pyridinyl group leaves us with a curiosity to investigate underlying ligand-binding mechanisms and dynamics using computational methods. Presented in this study are insights that clearly explain the effects of structural SF5 -aniline→CF3 -pyridinyl modifications on pfDHODH inhibition. Findings showed that the CF3 -pyridinyl group induced an optimal and stabilized positioning of DSM421 within the binding pocket, allowing for steady and strong intermolecular interactions which favored its stronger binding affinity as estimated and correlated with bioactivity data. These interactions consequently induced a pronounced stabilization of the structural conformation of pfDHODH by restricting residue motions, which possibly underpinned its enhanced inhibitory activity relative to DSM265. Active site interactions of the CF3 -pyrinidyl group with residues Ser236, Ile237, and Phe188 characterized by strong π-π stacking and halogen interactions also stabilized its positioning which altogether accounted for its enhanced inhibitory prowess towards pfDHODH. On the contrary, fewer and weaker interactions characterized DSM265 binding which could explain its relatively lower binding affinity. Findings will facilitate the design of novel pfDHODH inhibitors with enhanced properties.

Investigation of ketonic effect in molecular interactions of 2-methylcyclohexanone with aniline, N-methyl aniline and N,N-dimethyl aniline at various temperatures

Densities (ρ) and speeds of sound (u) and viscosities (η) of binary mixtures of 2-methoxy aniline with aniline, N-methyl aniline and N, N-dimethyl aniline including those of pure liquids, over the entire composition range were measured at temperatures (303.15, 308.15 and 313.15) K and 101.3 kPa. Using the experimental data, the excess volume (VE ) and excess isentropic compressibility (κs E ), deviation in viscosity (Δη), excess partial molar volumes, and and excess partial molar isentropic compressibilities, and of the components at infinite dilution were calculated. These values indicate the formation of intermolecular hydrogen bonding (N-H·····O = C) between the hydrogen atom of amine group of aniline /N-methyl aniline /N, N-dimethyl aniline and the oxygen atom of carbonyl group of 2-methylcyclohexanone in the binary liquid mixtures.

Electronic g-tensors of nanodiamonds: Dependence on the size, shape, and surface functionalization.

The electronic g-tensor dependence on the size, shape, and surface functionalization of nanodiamonds (NDs) is theoretically investigated by selecting dangling bonds and single substitutional nitrogen atoms as a main source of the unpaired electrons. The performed g-tensor calculations reveal that aforementioned paramagnetic impurities introduced into octahedrally shaped ND of C84H64 size behave in a very similar manner as those embedded into a smaller octahedral model of C35H36 size. Since cubic and tetrahedral NDs-C54H48 and C51H52-demonstrate a wider range of g-shift values than octahedral systems, the g-tensor dependence on different shapes can be considered as more pronounced. However, a different surface functionalization scheme, namely, fluorination, results in a much larger variation of the g-shifts, pointing to a significant impact the F atoms have on the local environment of the unpaired electrons in C35F36. A partial surface functionalization of C35H36 with benzoic acid and aniline groups indicates that, in some special cases, these linkers might induce a noticeable spin density redistribution which in turn substantially modifies the g-shift values of the system. Additional infrared (IR) spectra calculations show that some of paramagnetic defects in C35H36 and C35F36 possess clearly expressed signatures which could be useful while analyzing the experimental IR spectra of NDs.

Adsorption properties, the pH-sensitive release of 5-fluorouracil and cytotoxicity studies of mesoporous silica drug delivery matrix

Mesoporous silica materials were investigated as the carriers for pH-sensitive drug delivery systems. Porous silica SBA-15 was first functionalized by anchoring N-[3-(trimethoxysilyl) propyl] aniline groups on the surface. After loading of an antineoplastic agent 5-fluorouracil, the pores were capped by β-cyclodextrin molecules. The studied samples were characterized by N2 adsorption/desorption measurements, thermal analysis, powder X-Ray Diffraction, and Transmission Electron Microscopy. Adsorption properties of 5-fluorouracil were explored via the construction of adsorption isotherms. The amount of 5-FU adsorbed on amine-functionalized SBA-15 was 60 mg per 1 g of solid. The adsorption of 5-fluorouracil on silica was also monitored by microcalorimetry, showing low adsorption enthalpies. Drug release properties from matrices were studied using UV–Visible spectroscopy with the un-blocked and blocked pores configuration to demonstrate the efficiency of the pH-responsive nanovalves and evaluated using different kinetic models. It was shown that no drug release occurred at neutral pH and that more than 80% of drug adsorbed amount was released at pH = 5. Working at the equilibrium, the initial burst of the drug from the silica surface, usually observed in other porous silica drug delivery systems, was avoided. The interaction between the β-cyclodextrin molecules and grafted amine functions were also studied as a function of pH. Finally, the cytotoxicity tests were performed using human glioma U87 MG cells.

Rate Constants and Mechanisms of the Reactions of Cl• and Cl2•– with Trace Organic Contaminants

Cl• and Cl2•- radicals contribute to the degradation of trace organic contaminants (TrOCs) such as pharmaceutical and personal care products and endocrine-disrupting chemicals. However, little is known about their reaction rate constants and mechanisms. In this study, the reaction rate constants of Cl• and Cl2•- with 88 target compounds were determined using laser flash photolysis. Decay kinetics, product buildup kinetics, and competition kinetics were applied to track the changes in their transient spectra. Cl• exhibited quite high reactivity toward TrOCs with reaction rate constants ranging from 3.10 × 109 to 4.08 × 1010 M-1 s-1. Cl2•- was less reactive but more selective, with reaction rate constants varying from <1 × 106 to 2.78 × 109 M-1 s-1. Three QSAR models were developed, which were capable of predicting the reaction rate constants of Cl2•- with TrOCs bearing phenol, alkoxy benzene, and aniline groups. The detection of Cl•-adducts of many TrOCs suggested that Cl• addition was an important reaction mechanism. Single electron transfer (SET) predominated in reactions of Cl• with TrOCs bearing electron-rich moieties (e.g., sulfonamides), and their cation radicals were observed. Cl• might also abstract hydrogen atoms from phenolic compounds to generate phenoxyl radicals. Moreover, Cl• could react with TrOCs through multiple pathways since more than one transient intermediate was detected simultaneously. SET was the major reaction mechanism of Cl2•- reactions with TrOCs bearing phenols, alkoxy benzenes, and anilines groups. Cl2•- was found to play an important role in TrOC degradation, though it has been often neglected in previous studies. The results improve the understanding of halogen radical-involved chemistry in TrOC degradation.

Theoretical Study on Asymmetric [2 + 2] Cycloaddition of an Alkynone with a Cyclic Enol Silyl Ether Catalyzed by a Chiral N,N′-Dioxide-Zn(II) Complex

The reaction mechanism and enantioselectivity of the asymmetric [2 + 2] cycloaddition between an alkynone (R1) and a cyclic enol silyl ether (R2) were studied theoretically by the DFT method at the B3LYP-D3(BJ)/6-311G**(CH2Cl2,SMD)//B3LYP-D3(BJ)/def2-SVP(CH2Cl2,SMD) theoretical level. The noncatalytic reaction occurred via a stepwise mechanism. The first C–C bond was constructed by coupling two pseudo radical centers generated at the most nucleophilic C2 atom in the cyclic enol silyl ether and the most electrophilic terminal Cβ atom in the alkynone, which was responsible for the regioselectivity of the reaction. The counterion NTf2– could stabilize the Zn(II) complex by coordinating to the center metal, forming a high-reactivity hexacoordinate Zn(II)-complex intermediate. The bulky CF3 group in the NTf2– ion adjusted the blocking effect of o-iPr in aniline of the ligand toward the reactive site (that is, the Cβ atom in the alkynone) and induced the si face of the cyclic enol silyl ether to approach the alkynone from its less hindered re face, achieving a high enanotioselectivity of products. The Pauli repulsion between the Zn(II)-associated moiety and cyclic enol silyl ether fragment was the main contributor to the stereodifference of the two competing pathways in chiral N,N′-dioxide-Zn(II)-catalyzed [2 + 2] cycloaddition. The unfavorable steric repulsion between the o-iPr group of aniline in the ligand and tert-butyldimethylsilyl (TBS) in the cyclic enol silyl ether along the re face path translated into a more destabilizing ΔEPauli value, leading to the predominant cycloaddition product (P-RR) observed in experiments. Variation of the linkage and chiral backbone could affect the repulsion among the o-iPr in the ligand, the counterion NTf2–, and substrates, leading to different stereochemical outcomes. These results are in good agreement with experimental observations.

Interaction of dimethyl carbonate with anilines in the presence of potassium methylate: Kinetics and the role of the base

AbstractThe kinetic patterns of the reaction between dimethyl carbonate and anilines in the presence of a potassium methylate as a catalyst were studied. The mechanism of aminolysis was clarified, which includes the detachment of the proton from the amino group of aniline and the subsequent attack of the resulting anion on the carbonyl group of dimethyl carbonate. It is shown that when the reaction occurs in the dimethyl carbonate‐methanol 3:1 system, the process can be described as an irreversible first‐order reaction in the aniline though the target reaction is complicated by side interaction between potassium methylate and dimethyl carbonate. The rate constants of the target reaction with substituted anilines and of the side reaction in the temperature range of 70‐90°C were determined. It is shown that the influence of the substituent on the reaction rate is described by the Hammett equation, with the constant of the reaction series being positive and the best correlation being achieved for σ‐scale. The results obtained are consistent with the proposed mechanism of the reaction and are explained by the facilitation of the aniline deprotonation with increasing acceptor properties of the substituent. Effective activation energies for the reaction of various anilines with dimethyl carbonate are found.