Oxygen Analog Research Articles

Insights Into the Gas-Phase Structure and Internal Dynamics of Diphenylsilane: A Broadband Rotational Spectroscopy Study.

The rotational spectrum of diphenylsilane was investigated using chirped-pulse Fourier transform microwave spectroscopy in the frequency range of 2-8 GHz. The lowest energy structure of diphenylsilane has C point group symmetry with the C symmetry axis coinciding with the -inertial axis of the molecule. Through the assignment of the main isotopologue as well as singly substituted heavy-atom isotopologues, including C, Si, and Si, we were able to obtain a comprehensive gas-phase structure of diphenylsilane. The structure of diphenylsilane was compared with its oxygen analogue, diphenylether, including a discussion of the barrier height to the large-amplitude motion of the phenyl rings. Furthermore, the structural comparison was extended to include a range of C-Si bond lengths and bond angles from other organosilicon molecules where the silicon atom is bonded to aliphatic and/or aromatic moieties.

Aromatic Difluoroboron β-Ketoiminate Complexes: Effect of Substituents on Mechanofluorochromism and Polymorphic Behavior.

Aromatic difluoroboron β-ketoiminate complexes (ketimBF2) are structural nitrogen-containing analogues of aromatic difluoroboron β-diketonates (diketBF2). Aggregation-induced emission (AIE) and polymorphic behavior allow ketimBF2 to exhibit mechanofluorochromic (MFC) properties. A detailed comparative study of the luminescence of a wide range of ketimBF2 with H- and CH3-substituents of nitrogen atom and diketBF2 with various substituents of the chelate ring (methyl, phenyl, toluoyl, anisoyl, biphenyl, naphthyl, anthracyl) in the solid state was carried out. As a result, regularities of the influence of substituents on the luminescent and MFC properties for 21 dyes have been established. Replacing one oxygen atom in diketBF2 with nitrogen atom in the chelate ring (H-substituted ketimBF2) changes the nature of the molecular stacking in crystals, which is manifested in different MFC properties. The introduction of a methyl group into the chelate ring (CH3-substituted ketimBF2) induces steric hindrance, which prevents the efficient formation of supramolecular structures and, consequently, leads to the shortest-wavelength monomeric emission in the solid state in comparison with oxygen and H-substituted nitrogen analogues. Methoxy derivative of H-substituted ketimBF2 exhibits non-reversible fluorochromic switching after annealing and can be used as temperature indicator to control unauthorized heating of temperature-sensitive substances during transportation and storage.

Synchronous Fluorescence Spectrometry (SFS) with Multivariate Calibration for the Determination of Polycyclic Aromatic Hydrocarbons (PAHs) and Their Oxygen Analogs in Printer Toner

Synchronous molecular fluorescence with multivariate calibration was investigated to assay seven polycyclic aromatic hydrocarbons (PAHs) and three oxygenated derivatives (O-PAHs) in printer toner. Great sensitivity and a good data compression capacity were achieved; therefore, a relatively small number of factors were used. Correlation coefficients above 0.95 for the calibration functions were obtained, and recoveries lie between 70 and 130% in analyzing synthetic samples (13 PCs). For the real samples assayed, recoveries between 81 and 125% were obtained when compared to the results obtained by gas chromatography – tandem mass spectrometry (GC-MS/MS). Despite a certain loss in accuracy when compared to chromatography, the proposed methodology is faster, simpler, and lower in cost. The multivariate tool proved to be an expeditious alternative for screening toner in relation to the presence and abundance of PAHs and derivatives.

Visible‐Light‐Mediated Oxidative Desulfurization‐Oxygenation in Cyclic Thio‐Amide

AbstractVisible‐light assisted a very simple and mild protocol for photocatalytic oxidative transformation of thioamide to amide group has been realized in cyclic system. For this purpose 5‐arylalkylidene‐rhodanine derivatives were chosen as model substrates to afford thiazolidine‐2,4‐diones. Light mediated reactions are intrinsically beneficial, since activation occurs by cleanest energy source light. Here K2S2O8 is used as terminal oxidant which does not leave any hazardous and corrosive waste to discard after the reaction fostering the practices of green chemistry. This is the first report of conversion of thioxo group in rhodanine derivatives into the corresponding oxygen analogue by visible light photo‐catalytic method. The reaction was very general since various 5‐arylalkylidene‐rhodanines underwent the reaction smoothly affording high product yields. Moreover, the broadness of this protocol was further established by applying this reaction on other systems like 3,4‐dihydropyrimidine‐2(1H)‐(thio)ones.

Convenient transformation of thioamides and thioketones to their oxygen analogues with singlet oxygen generated from trans-5-hydroperoxy-3,5-dimethyl-1,2-dioxolan-3-yl ethaneperoxate

ABSTRACT An efficient method for the oxidative transformation of thioamides and thioketones to their oxygen analogues with singlet oxygen is reported. Singlet oxygen was produced in situ from the fragmentation of the trans-5-hydroperoxy-3,5-dimethyl-1,2-dioxolane-3-yl ethaneperoxate in the presence of KOH, and it has been explored as an effective oxidant for oxidative desulfurization of thioamides and thioketones. This protocol provides amides and ketones in excellent yields (80–90%) at room temperature under mild conditions. The thioamides reacted very well with this reagent system. The conjugation of neighboring NH and C=S groups appears to enhance yields for thioamides. Further investigation showed that this reagent system is also an efficient system for deprotection of thionoesters to esters.

Benzo[d][1,2,3]oxadithiole 2-Oxide

A simplified synthesis of the title compound is reported and its 1H and 13C NMR data are fully assigned including determination of H–H and C–H coupling constants. Its X-ray structure has been determined for the first time. NMR data are also presented for the oxygen analogue.

Recent Advances in the Palladium‐Catalyzed Synthesis of Unnatural Tryptophans

AbstractUnnatural tryptophans are introduced to explore and engineer the dynamics, function and properties of modified proteins because of intrinsic fluorescence decay, participation in various π‐system interactions, and high occurrences of tryptophan nucleolus in proteins. Due to its role in protein stability and utility as a fluorophore, it becomes a useful unit for protein studies. Several unnatural tryptophans including the oxygen and sulfur analogues have been constructed as endogenous tryptophan analogues to modify the fluorescent character with minimal perturbation to the native structure, while others have been synthesized to probe the cellular mechanisms of protein synthesis. A number of efficient methods for the construction of this important building block, including Larock indolisation, Heck coupling, Negishi coupling and Sonagashira coupling followed by cyclisation have been widely studied and patented as well, by different research groups. Surprisingly, there is a scarcity of any comprehensive reviews on palladium catalyzed synthesis of unnatural tryptophans. Therefore, we summarized the development of different palladium catalysts, ligands and synthetic approaches for the unnatural tryptophans from 2005 to the most recent results. To the best of our knowledge, this is the first review on the synthesis of unnatural tryptophans.

Chemistry, Metabolism and Neurotoxicity of Organophosphorus Insecticides: A Review

Organophosphorus compounds (OPs) are phosphoric acid derivatives represented by the formula (R2XP=O/S), R as organic groups; however, they need not contain a direct carbon-phosphorus bond. The organophosphorus compounds can be categorized into three classes, viz., organophosphates, carbamates nerve agents. The OPs having application as insecticides are generally phosphorothioates (i.e., containing P=S bond). These sulfur analogs are first bioactivated (in vivo) and converted to oxygen analogs responsible for exerting toxic action. These organophosphorus compounds are esters, fluorides, anhydrides, and amides of phosphoric, phosphorothioate, and phosphorodithioic acids. The toxicity of OPs is related to their molecular structure, metabolism in the targeted organisms, concentration, mode of decomposition, application, ingestion in organisms, etc. Exposure to OPs leads to the appearance of neurological symptoms followed by acute poisoning by targeting the target primarily, acetylcholine (AChE). However, secondary targets and other harmful effects besides nerve system problems are also reported. Organophosphates poison insects and other animals, including birds, amphibians, and mammals. These chemicals can have neural effects (Neurotoxicity), non-neuronal effects, or acute toxicity, which may also result in fatality. Their uncontrollable widespread became a significant threat to the environment; thus, corrective measures have been essential to save living beings and the environment from further damage.

Determination of Polycyclic Aromatic Hydrocarbons (PAHs) and Sulfur, Nitrogen, and Oxygen Analogs in Fumes from Heated Asphalt by High-Performance Liquid Chromatography – Diode Array Detection (HPLC-DAD)

Polycyclic aromatic hydrocarbons (PAHs), as well as their sulfur (S-PAHs), oxygen (O-PAHs), and nitrogen (N-PAHs) analogs were evaluated in the fumes of asphalt samples produced in Brazilian refineries. The fumes were generated using a laboratory-constructed device for extraction and collection (DEC). Two previously published methodologies for PAHs and S-PAHs evaluation by high-performance liquid chromatography with diode array detection (HPLC-DAD) were employed, together with a new methodology for O and N-PAHs. A total of 54 compounds were assessed. The samples included 31 compounds within the scope of this study, and the emissions were highly dependent upon the heating temperature and asphalt source.

Increasing the Sodium Metal Electrode Compatibility with the Na3 PS4 Solid-State Electrolyte through Heteroatom Substitution.

Rechargeable batteries are essential to the global shift towards renewable energy sources and their storage. At present, improvements in their safety and sustainability are of great importance as part of global sustainable development goals. A major contender in this shift are rechargeable solid-state sodium batteries, as a low-cost, safe, and sustainable alternative to conventional lithium-ion batteries. Recently, solid-state electrolytes with a high ionic conductivity and low flammability have been developed. However, these still face challenges with the highly reactive sodium metal electrode. The study of these electrolyte-electrode interfaces is challenging from a computational and experimental point of view, but recent advances in molecular dynamics neural-network potentials are finally enabling access to these environments compared to more computationally expensive conventional ab-initio techniques. In this study, heteroatom-substituted Na3 PS3 X1 analogues, where X is sulfur, oxygen, selenium, tellurium, nitrogen, chlorine, and fluorine, are investigated using total-trajectory analysis and neural-network molecular dynamics. It was found that inductive electron-withdrawing and electron-donating effects, alongside differences in heteroatom atomic radius, electronegativity, and valency, influenced the electrolyte reactivity. The Na3 PS3 O1 oxygen analogue was found to have superior chemical stability against the sodium metal electrode, paving the way towards high-performance, long lifetime and reliable rechargeable solid-state sodium batteries.

Synthesis, computational and experimental pharmacological studies for (thio)ether-triazine 5-HT6R ligands with noticeable action on AChE/BChE and chalcogen-dependent intrinsic activity in search for new class of drugs against Alzheimer's disease

Alzheimer's disease is becoming a growing problem increasing at a tremendous rate. Serotonin 5-HT6 receptors appear to be a particularly attractive target from a therapeutic perspective, due to their involvement not only in cognitive processes, but also in depression and psychosis. In this work, we present the synthesis and broad biological characterization of a new series of 18 compounds with a unique 1,3,5-triazine backbone, as potent 5-HT6 receptor ligands. The main aim of this research is to compare the biological activity of the newly synthesized sulfur derivatives with their oxygen analogues and their N-demethylated O- and S-metabolites obtained for the first time. Most of the new triazines displayed high affinity (Ki < 200 nM) and selectivity towards 5-HT6R, with respect to 5-HT2AR, 5-HT7R, and D2R, in the radioligand binding assays. For selected, active compounds crystallographic studies, functional bioassays, and ADME-Tox profile in vitro were performed. The exciting novelty is that the sulfur derivatives exhibit an agonistic mode of action contrary to all other compounds obtained to date in this chemical class herein and previously reported. Advanced computational studies indicated that this intriguing functional shift might be caused by presence of chalcogen bonds formed only by the sulfur atom. In addition, the N-demethylated derivatives have emerged highly potent antioxidants and, moreover, show a significant improvement in metabolic stability compared to the parent structures. The cholinesterase study present micromolar inhibitory AChE and BChE activity for both 5-HT6 agonist 19 and potent antagonist 5. Finally, the behavioral experiments of compound 19 demonstrated its antidepressant-like properties and slight ability to improve cognitive deficits, without inducing memory impairments by itself. Described pharmacological properties of both compounds (5 and 19) allow to give a design clue for the development of multitarget compounds with 5-HT6 (both agonist and antagonist)/AChE and/or BChE mechanism in the group of 1,3,5-triazine derivatives.

Mannich reaction involving 6-amino-4-methyl2-(thio)oxo-1,2-dihydropyridine-3,5-dicarbonitriles

The reaction of (1-ethoxyethylidene)malononitrile with cyanoacetamide or cyanothioacetamide yielded 6-amino4-methyl-2-(thio)oxo-1,2-dihydropyridine-3,5-dicarbonitriles. The resulting pyridine derivatives enter into an aminomethylation reaction with an excess of formaldehyde and primary amines with the formation of previously unknown 8-methyl-6-oxo-3-R-1,3,4,6-tetrahydro-2 H -pyrido[1,2- a ][ 1,3,5]triazine-7,9-dicarbonitriles. Further treatment of 6-amino-4-methyl-2-thioxo-1,2-dihydropyridine-3,5-dicarbonitrile and its oxygen analogue with excess formaldehyde leads to the formation of 3,10-dimethyl-1,8-dithioxo-5,6,12,13-tetrahydro-1 H ,8 H -dipyrido[1,2- a :1’,2’- e ][1,3,5,7]tetrazocin-2,4,9,11-tetracarbonitrile and 6,6’-[methylenedi(imino)]bis(4-methyl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile), respectively. These compounds show a pronounced antidote effect against the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) in laboratory and field experiments on sunflower seedlings. Also, 6-amino-4-methyl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile exhibits pronounced anticorrosion properties and is an adsorption-type corrosion inhibitor. The mechanism of anti-corrosion action was studied in detail using X-ray photoelectron spectroscopy.

Theoretical insights on pyrene end-capped thiophenes/furans and their suitability towards optoelectronic applications

Organic semiconductors are attractive candidates for the development of flexible and efficient optoelectronic devices. In this work, we have studied the pyrene end-capped thiophene derivatives with different number of oligomeric rings and substituted with their oxygen analogue furan. Results indicate that the molecular planarity varies with the substitution of furan rings and the number of rings play a role on optoelectronic property of the systems. All the systems have shown ambipolar behavior, but the high charge barrier in the case of electrons could limit the device performance. Further, in photovoltaic analysis the increment in oligomeric ring has substantially reduces the open circuit voltage and the fill factor. However, the introduction of furan has improved the overall light harvesting efficiency. With the proper choice of material and device engineering the shorter systems can be considered for photovoltaics, where as the longer derivatives can be considered for light emitting device applications.

3-Methyl-1-phenyl-4-thioacetylpyrazol-5-one

The novel compound 3-methyl-1-phenyl-4-thioacetylpyrazol-5-one is obtained in excellent yield via a thionation of the corresponding oxygen analogue. The product is isolated in pure form using column chromatography and is characterised using 1D and 2D NMR experiments, ATR IR and HRMS spectra, and single-crystal XRD.

D-A-D-based Unsymmetrical Thiosquaraine Dye for the Dye-Sensitized Solar Cells†.

In dye-sensitized solar cell, modulating the electronic properties of the sensitizer by varying the donor, π-spacer, acceptor and anchoring groups help optimizing the structure of the dye for better device performance. Here, a donor-acceptor-donor-based unsymmetrical thiosquaraine sensitizer (SQ5S) has been designed and synthesized. Photophysical, electrochemical, theoretical and photovoltaic characterizations of SQ5S dye have been compared with its oxygen analog, SQ5. The incorporation of the sulfur atom in the acceptor unit of SQ5S dye showed an intense peak at 688 nm, which was 38 nm of red-shifted and showed the panchromatic light harvesting response with the onset of 850 nm compared with SQ5 dye. The LUMO and HOMO energy levels are well aligned with the conduction band of TiO2 and the redox potential of electrolyte for the charge injection and the dye-regeneration processes, respectively. Photovoltaic efficiency of 1.51% (VOC 610 mV, JSC 3.07 mA cm-2 , ff 81%) has been achieved for SQ5S dye, whereas SQ5 showed thedevice performance of 5.43% (VOC 723 mV, JSC 9.3 mA cm-2 , ff 80%). The decreased device performance for the dye SQ5S has been attributed to the favorable intersystem crossing process associated with the photoexcited SQ5S that reduces the driving force for the charge injection process.

Differential Metabolomics Reveals Pathogenesis of Pestalotiopsis kenyana Causing Leaf Spot Disease of Zanthoxylum schinifolium.

Pepper leaf spot is a common disease of Zanthoxylum schinifolium. When it is serious, it directly affects the growth of Z. schinifolium, making the plant unable to blossom and bear fruit, which seriously restricts the development of the Z. schinifolium industry. Therefore, the pathogenic mechanism of leaf spots should be explored to provide a basis for a comprehensive understanding of the disease. Using liquid chromatography-mass spectrometry (LC-MS) technology combined with the data-dependent acquisition, the full spectrum analysis of pathogen mycelium samples was carried out. Partial least squares discriminant analysis (PLS-DA) was used to reveal the differences in metabolic patterns among different groups. Hierarchical clustering analysis (HCA) and PLS-DA were used to reveal the relationship between samples and metabolites, which reflected the metabolomics changes of Pestalotiopsis kenyana in the logarithmic growth phase of mycelia, the stable growth phase of mycelia, the massive spore stage, the induction culture conditions of PDA and Z. schinifolium leaves, and the possible pathogenic substances were selected for pathogenicity detection. PLS-DA had a strong predictive ability, indicating a clear analysis trend between different groups. The results of the metabolomics analysis showed that the differential metabolites of pathogenic bacteria were abundant at different stages and under different medium conditions, and the content of metabolites changed significantly. There were 3922 differential metabolites in nine groups under positive and negative ion modes, including lipids and lipid molecules, organic acids and their derivatives, organic heterocyclic compounds, organic oxygen compounds, carbohydrate polyketides, nucleosides, nucleotides, and analogs. The results of the pathogenicity test showed that the leaves treated with 3,5-dimethoxy benzoic acid, S-(5-adenosy)-l-homocysteine, 2-(1H-indol-3-yl) acetic acid, l-glutamic acid, and 2-(2-acetyl-3,5-dihydroxy phenyl) acetic acid showed different degrees of yellowish-brown lesions. This indicated that these substances may be related to the pathogenicity of P. kenyana, and the incidence was more serious when treated with 3,5-dimethoxybenzoic acid and S-(5-adenosy)- l -homocysteine. This study provides a basis for further analysis of differential metabolites and provides a theoretical reference for the prevention and treatment of Z. schinifolium leaf spot.

Bis(thio)carbohydrazone Luminogens with AIEE and ACQ Features and Their In Silico Investigations with SARS-CoV-2.

Herein, we report two novel multidentate luminogen proligands bis(3,5‐diiodosalicylidene) carbohydrazone (H4L1) and bis(3,5‐diiodosalicylidene) thiocarbohydrazone (H4L2), which are suitable candidates for biomedical applications. Though the thiocarbohydrazone H4L2 shows aggregation caused quenching (ACQ), the carbohydrazone H4L1 exhibits stronger fluorescence due to aggregation induced emission enhancement (AIEE). Molecular docking studies of H4L1 and H4L2 along with four similar (thio)carbohydrazones with the active sites of SARS‐CoV‐2 main protease 3CLpro reveals that the thiocarbohydrazones, in general, are showing better propensity compared to their oxygen analogues. Both the thiocarbohydrazones and the carbohydrazones, however, exhibit better binding potential at the active sites than that of some of the repurposed drugs such as chloroquine, hydroxychloroquine, lopinavir, ritonavir, darunavir and remdesivir. Also, the carbohydrazone H4L1 can be a better bioprobe compared to H4L2 as the former is found to have better binding potential with SARS‐CoV‐2 spike glycoprotein along with AIEE feature.

A Terphenyl Supported Dioxophosphorane Dimer: the Light Congener of Lawesson's and Woollins' Reagents.

Thermolysis of a 1,3‐dioxa‐2‐phospholane supported by the terphenyl ligand AriPr4 (AriPr4=[C6H3‐2,6‐(C6H3‐2,6‐iPr2)]) at 150 °C gives [AriPr4PO2]2 via loss of ethene. [AriPr4PO2]2 was characterised by X‐ray crystallography and NMR spectroscopy; it contains a 4‐membered P−O−P−O ring and is the isostructural oxygen analogue of Lawesson's and Woollins’ reagents. The dimeric structure of [AriPr4PO2]2 was found to persist in solution through VT NMR spectroscopy and DOSY, supported by DFT calculations. The addition of DMAP to the 1,3‐dioxa‐2‐phospholane facilitates the loss of ethene to give AriPr4(DMAP)PO2 after days at room temperature, with this product also characterised by X‐ray crystallography and NMR spectroscopy. Replacement of the DMAP with pyridine induces ethene loss from the 1,3‐dioxa‐2‐phospholane to provide gram‐scale samples of [AriPr4PO2]2 in 75 % yield in 2 days at only 100 °C.

Chalcogen bearing tetrasubstituted zinc (II) phthalocyanines for CT26 colon carcinoma cells photodynamic therapy

The synthesis and photochemical properties of six new lipophilic chalcogen tetrasubstituted zinc (II) phthalocyanines and their corresponding water-soluble cationic derivatives were investigated for CT26 colon carcinoma cells photodynamic therapy. Sulfur and selenium phthalocyanines Q-bands are red shifted around 10 nm with respect to the Q-band of oxygen phthalocyanines. The introduction of Se atoms in peripheral position generates non-significant shifts in the absorption spectrum compared to S-bearing phthalocyanine. In addition, Q-band absorption coefficient of selenium phthalocyanines showed to be higher than their respective sulfur and oxygen analogs, which is relevant for dosing in PDT studies. The fluorescence emission maximum wavelength showed the same trend regards to the presence of chalcogen atoms, O < Se < S. All phthalocyanines are efficient singlet oxygen generators with values in the range 0.42–0.75. In most cases, increasing the atomic number of chalcogen atoms produces a rise of singlet oxygen production efficiency. The replacement of O for S or Se atoms cause a red shifting around 20 nm of triplet-triplet maximum absorption wavelength and the introduction of Se atoms causes a significant shortening of τT. The photodynamic effect was evaluated on CT26 colon carcinoma cells. Oxygen phthalocyanines triggered cell death both in the absence or presence of light, whereas sulfur and selenium phthalocyanines diminished cell viability in a concentration dependent manner only after light exposure. S-bearing phthalocyanines showed the best photodynamic efficiency among all novel phthalocyanines.

Adventures in 1,3-Selenazole Chemistry

AbstractThe synthesis of 1,3-selenazoles and related compounds, including 2,4,5-trisubstituted, 2,4-disubstituted, 4,5-disubstituted, 4-substituted 1,3-selenazoles, and parent unsubstituted 1,3-selenazole, is highlighted. Emphasis is also given on 2-benzoyl-1,3-selenazoles which can be functionalized by Knoevenagel reactions or by rearrangements via their corresponding oximes. Syntheses of bis-, tris-, and tetrakis(1,3-selenazoles) are discussed as well. 1,3,4-6H-Selenadiazines are available from selenosemicarbazides and can undergo ring-contraction or deselenation reactions. Most syntheses rely on the application of selenocarboxylic amides, selenourea and related building blocks which are conveniently available by reaction of the corresponding oxygen analogues with P4Se10.1 Introduction2 Selenocarboxylic Amides3 2,4,5-Tri- and 2,4-Disubstituted 1,3-Selenazoles4 Bis(1,3-selenazoles)5 2-Amino-1,3-selenazoles6 2-Unsubstituted 1,3-Selenazoles7 1,3,4-Selenadiazines8 Conclusions