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Molecules (Basel, Switzerland) Feb 2020The exceptional reactivity of the azide group makes organic azides a highly versatile family of compounds in chemistry and the material sciences. One of the most... (Review)
Review
The exceptional reactivity of the azide group makes organic azides a highly versatile family of compounds in chemistry and the material sciences. One of the most prominent reactions employing organic azides is the regioselective copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition with alkynes yielding 1,2,3-triazoles. Other named reactions include the Staudinger reduction, the aza-Wittig reaction, and the Curtius rearrangement. The popularity of organic azides in material sciences is mostly based on their propensity to release nitrogen by thermal activation or photolysis. On the one hand, this scission reaction is accompanied with a considerable output of energy, making them interesting as highly energetic materials. On the other hand, it produces highly reactive nitrenes that show extraordinary efficiency in polymer crosslinking, a process used to alter the physical properties of polymers and to boost efficiencies of polymer-based devices such as membrane fuel cells, organic solar cells (OSCs), light-emitting diodes (LEDs), and organic field-effect transistors (OFETs). Thermosets are also suitable application areas. In most cases, organic azides with multiple azide functions are employed which can either be small molecules or oligo- and polymers. This review focuses on nitrene-based applications of multivalent organic azides in the material and life sciences.
Topics: Alkynes; Azides; Catalysis; Cross-Linking Reagents; Cycloaddition Reaction; Humans; Materials Science; Molecular Structure; Nitrogen; Photochemical Processes; Photolysis; Triazoles
PubMed: 32102403
DOI: 10.3390/molecules25041009 -
Molecules (Basel, Switzerland) Dec 2020Tea is rich in catechins and aluminum. In this study, the process of catechin photolysis was applied as a model for examining the effects of aluminum chloride (AlCl) on...
Tea is rich in catechins and aluminum. In this study, the process of catechin photolysis was applied as a model for examining the effects of aluminum chloride (AlCl) on the structural changes of catechin and the alteration of aluminum complexes under blue light irradiation (BLI) at pH 8 using liquid chromatography and mass spectrometry techniques. Additionally, the effects of anions on catechin upon the addition of AlCl and treatment with BLI were also studied. In this study, when 1 mM catechin was treated with BLI, a superoxide anion radical (O2•-) was generated in an air-saturated aqueous solution, in addition to forming a dimeric catechin (proanthocyanidin) via a photon-induced redox reaction. The relative percentage of catechin was found to be 59.0 and 95.7 for catechin treated with BLI and catechin upon the addition of 1 mM AlCl treated with BLI, respectively. It suggested that catechin treated with BLI could be suppressed by AlCl, while AlCl did not form a complex with catechin in the photolytic system. However, under the same conditions, it was also found that the addition of AlCl inhibited the photolytic formation of O2•-, and reduced the generation of proanthocyanidin, suggesting that the disconnection of proanthocyanidin was achieved by AlCl acting as a catalyst under treatment with BLI. The influence of 1 mM fluoride (F-) and 1 mM oxalate (C2O42-) ions on the photolysis of 1 mM catechin upon the addition of 1 mM AlCl and treatment with BLI was found to be insignificant, implying that, during the photolysis of catechin, the Al species were either neutral or negatively charged and the aluminum species did not form a complex with anions in the photolytic system. Therefore, aluminum, which is an amphoteric species, has an inherent potential to stabilize the photolysis of catechin in an alkaline conditions, while suppressing the O2•- and proanthocyanidin generation via aluminum ion catalysis in the catechin/Al system under treatment with BLI.
Topics: Aluminum; Aluminum Chloride; Catechin; Chromatography, Liquid; Light; Mass Spectrometry; Photolysis; Plants; Proanthocyanidins; Superoxides; Tea
PubMed: 33348758
DOI: 10.3390/molecules25245985 -
Chemosphere Jun 2017This study investigated the i) kinetics, and ii) proportion of photolysis of 30 relatively stable active pharmaceutical ingredients (APIs) during artificial UV...
This study investigated the i) kinetics, and ii) proportion of photolysis of 30 relatively stable active pharmaceutical ingredients (APIs) during artificial UV irradiation for 28 d in ammonium acetate buffer, filtered and unfiltered river water. Buffer was included to control removal kinetics under stable pH conditions and without particulate matter. Dark controls were used to determine removal due to other processes than photolysis and calculate the proportion of photolysis of the total removal. The removal of each API in each matrix was determined using online solid phase extraction/liquid chromatography tandem mass spectrometry (online SPE/LC-MS/MS). Most APIs transformed during the 28 d of UV irradiation and the dark controls showed that photolysis was the major removal process for the majority of the APIs studied. The half-lives ranged from 6 h (amitriptyline) in unfiltered river water to 884 h (37 d, carbamazepine) in buffer. In unfiltered river water, the proportion of APIs with short half-lives (<48 h) was much higher (29%) than in the other matrices (4%), probably due to additional organic carbon, which could have promoted indirect photolysis. Furthermore, two APIs, memantine and fluconazole, were stable in all three matrices, while alprazolam was stable in buffer and unfiltered river water and four additional APIs were stable in buffer. Considering the relatively long-term UV-exposure, this study enabled the investigation of environmentally relevant half-lives in natural waters. Many APIs showed high persistence, which is environmentally concerning and emphasizes the importance of further studies on their environmental fate and effects.
Topics: Drug Stability; Environmental Restoration and Remediation; Half-Life; Kinetics; Pharmaceutical Preparations; Photolysis; Rivers; Solid Phase Extraction; Tandem Mass Spectrometry; Time Factors; Ultraviolet Rays; Water; Water Pollutants, Chemical
PubMed: 28260657
DOI: 10.1016/j.chemosphere.2017.02.063 -
Environmental Science & Technology May 2023Singlet oxygen (O) is an important reactive species in natural waters produced during photolysis of dissolved organic matter (DOM). Prior studies have demonstrated that...
Singlet oxygen (O) is an important reactive species in natural waters produced during photolysis of dissolved organic matter (DOM). Prior studies have demonstrated that O exhibits a microheterogeneous distribution, with [O] in the interior of DOM macromolecules ∼30 to 1000-fold greater than in bulk solution. The [O] profile for DOM-containing solutions has been determined mainly by the use of hydrophobic probes, which are not commercially available. In this study, we employed a dual-probe method combining the widely used hydrophilic O probe furfuryl alcohol (FFA) and its structural analogue furfuryl amine (FFAm). FFAm exists mainly as a cation at pH <9 and was therefore hypothesized to have an enhanced local concentration in the near-DOM phase, whereas FFA will be distributed homogeneously. The probe pair was used to quantify apparent [O] in DOM samples from different isolation procedures (humic acid, fulvic acid, reverse osmosis) and diverse origins (aquatic and terrestrial) as a function of pH and ionic strength, and all samples studied exhibited enhanced reactivity of FFAm relative to FFA, especially at pH 7 and 8. To quantify the spatial distribution of [O], we combined electrostatic models with Latch and McNeill's three-phase distribution model. Modeling results for Suwannee River humic acid (SRHA) yield a surface [O] of ∼60 pM, which is ∼96-fold higher than the aqueous-phase [O] measured with FFA. This value is in agreement with prior reports that determined 1-3 orders of magnitude higher [O] in the DOM phase compared to bulk solution. Overall, this work expands the knowledge base of DOM microheterogeneous photochemistry by showing that diverse DOM isolates exhibit this phenomenon. In addition, the dual-probe approach and electrostatic modeling offer a new way to gain mechanistic insight into the spatial distribution of O and potentially other photochemically produced reactive intermediates.
Topics: Singlet Oxygen; Amines; Humic Substances; Water; Photolysis; Dissolved Organic Matter
PubMed: 37130219
DOI: 10.1021/acs.est.3c01726 -
Angewandte Chemie (International Ed. in... Aug 2020Guanine radicals are important reactive intermediates in DNA damage. Hydroxyl radical (HO ) has long been believed to react with 2'-deoxyguanosine (dG) generating...
Guanine radicals are important reactive intermediates in DNA damage. Hydroxyl radical (HO ) has long been believed to react with 2'-deoxyguanosine (dG) generating 2'-deoxyguanosin-N1-yl radical (dG(N1-H) ) via addition to the nucleobase π-system and subsequent dehydration. This basic tenet was challenged by an alternative mechanism, in which the major reaction of HO with dG was proposed to involve hydrogen atom abstraction from the N2-amine. The 2'-deoxyguanosin-N2-yl radical (dG(N2-H) ) formed was proposed to rapidly tautomerize to dG(N1-H) . We report the first independent generation of dG(N2-H) in high yield via photolysis of 1. dG(N2-H) is directly observed upon nanosecond laser flash photolysis (LFP) of 1. The absorption spectrum of dG(N2-H) is corroborated by DFT studies, and anti- and syn-dG(N2-H) are resolved for the first time. The LFP experiments showed no evidence for tautomerization of dG(N2-H) to dG(N1-H) within hundreds of microseconds. This observation suggests that the generation of dG(N1-H) via dG(N2-H) following hydrogen atom abstraction from dG is unlikely to be a major pathway when HO reacts with dG.
Topics: Deoxyguanosine; Free Radicals; Hydroxyl Radical; Photolysis; Spectrophotometry, Ultraviolet; Ultraviolet Rays
PubMed: 32365264
DOI: 10.1002/anie.202005300 -
Molecules (Basel, Switzerland) Dec 2018Chloro- and dichloro-methylsulfonyl nitrenes, CH₂ClS(O)₂N and CHCl₂S(O)₂N, have been generated from UV laser photolysis (193 and 266 nm) of the corresponding...
Chloro- and dichloro-methylsulfonyl nitrenes, CH₂ClS(O)₂N and CHCl₂S(O)₂N, have been generated from UV laser photolysis (193 and 266 nm) of the corresponding sulfonyl azides CH₂ClS(O)₂N₃ and CHCl₂S(O)₂N₃, respectively. Both nitrenes have been characterized with matrix-isolation IR and EPR spectroscopy in solid N₂ (10 K) and glassy toluene (5 K) matrices. Triplet ground-state multiplicity of CH₂ClS(O)₂N (|/| = 1.57 cm and |/| = 0.0026 cm) and CHCl₂S(O)₂N (|/| = 1.56 cm and |/| = 0.0042 cm) has been confirmed. In addition, dichloromethylnitrene CHCl₂N (|/| = 1.57 cm and |/| = 0 cm), formed from SO₂-elimination in CHCl₂S(O)₂N, has also been identified for the first time. Upon UV light irradiation (365 nm), the two sulfonyl nitrenes R⁻S(O)₂N (R = CH₂Cl and CHCl₂) undergo concomitant 1,2-R shift to -sulfonlyamines R⁻NSO₂ and 1,2-oxygen shift to -nitroso compounds R⁻S(O)NO, respectively. The identification of these new species with IR spectroscopy is supported by N labeling experiments and quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level. In contrast, the thermally-generated sulfonyl nitrenes CH₂ClS(O)₂N (600 K) and CHCl₂S(O)₂N (700 K) dissociate completely in the gas phase, and in both cases, HCN, SO₂, HCl, HNSO, and CO form. Additionally, ClCN, OCCl₂, HNSO₂, •NSO₂, and the atmospherically relevant radical •CHCl₂ are also identified among the fragmentation products of CHCl₂S(O)₂N. The underlying mechanisms for the rearrangement and decomposition of CH₂ClS(O)₂N and CHCl₂S(O)₂N are discussed based on the experimentally-observed products and the calculated potential energy profile.
Topics: Electron Spin Resonance Spectroscopy; Isomerism; Light; Nitroso Compounds; Photolysis; Quantum Theory; Spectrophotometry, Infrared; Spectrum Analysis; Temperature
PubMed: 30551679
DOI: 10.3390/molecules23123312 -
International Journal of Environmental... Aug 2022The presence of polycyclic aromatic hydrocarbons (PAHs) on firefighters' personal protective equipment is a concern. One form of preventing from these compounds is to...
The presence of polycyclic aromatic hydrocarbons (PAHs) on firefighters' personal protective equipment is a concern. One form of preventing from these compounds is to decontaminate proximity firefighting protective clothing (PFPC). Traditional decontamination methods do not promote total removal of pollutants and alter the properties of PFPC. The objective of this work was to evaluate the effectiveness of white light-photolysis (WLP), an advanced oxidation process (AOP), for removing PAHs from PFPC, while maintaining the integrity of the fabric fibers. Experiments were carried out, varying reaction time and concentration of HO. With WLP (without HO), it was possible to remove more than 73% of the PAHs tested from the outer layer of PFPC in 3 days. The WLP provided the greatest removal of PAHs, compared with the most common mechanical decontamination techniques (laundering and wet-soap brushing). The fibers' integrity after exposure to the white light was evaluated with infrared spectroscopy and scanning electron microscopy/energy dispersive X-ray spectrometry. In addition, a tearing strength test was performed. No remarkable fabric degradation was observed, indicating a possible, routine-compatible, simple, and inexpensive method of decontamination of PFPC, based on photolysis, which is effective in the degradation of PAHs and maintains the integrity of fabric fibers.
Topics: Air Pollutants, Occupational; Firefighters; Fires; Hydrogen Peroxide; Occupational Exposure; Photolysis; Polycyclic Aromatic Hydrocarbons; Protective Clothing
PubMed: 36011697
DOI: 10.3390/ijerph191610054 -
Environmental Research Aug 2019In this work, we investigate the photolysis behavior of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (DDBQ), the only dibrominated benzoquinone detected in treated water so...
In this work, we investigate the photolysis behavior of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (DDBQ), the only dibrominated benzoquinone detected in treated water so far. DDBQ solutions prepared in ultra-pure water were exposed to UV radiation centered at 254 nm (UV), and the photolysis of the parent compound was monitored together with by-product formation. The DDBQ pseudo-first order photolysis rate constants decreased when increasing the initial DDBQ concentration, and this behavior was caused by saturation of absorption. The photodegradation kinetics was found not to depend on pH and 1-butanol addition, but was affected by humic acids and components that occur in both natural waters and treated wastewater. For the first time with this class of compounds, photolysis studies were also performed using natural and treated wastewater matrices, where photodegradation was always found to proceed significantly slower than in ultra-pure water. The implications for the radiation dose that is required to reach a given treatment target are discussed, and a numerical approach by which to foresee the extent of degradation inhibition is provided that should be taken into account when planning the UV treatment of DDBQ. The phototransformation of DDBQ yielded hydroxyderivatives, most likely via a debromination-hydroxylation pathway. In-silico toxicity screening suggested that the transformation of DDBQ into the detected hydroxyderivatives would not eliminate toxicity. Although the monohydroxylated derivative underwent relatively fast transformation, the dihydroxylated compound was found to accumulate during irradiation. As a compromise, the irradiation conditions that produce over 90% degradation of DDBQ in the studied samples, and at the same time keep by-product formation low are discussed.
Topics: Benzoquinones; Kinetics; Photochemical Processes; Photolysis; Ultraviolet Rays; Wastewater; Water; Water Pollutants, Chemical
PubMed: 31150933
DOI: 10.1016/j.envres.2019.05.018 -
Organic Letters May 2019In an ongoing effort to study the environmental fate of endocrine-active steroid hormones, we report the formation of phenolic rearrangement products (3 and 4) with a...
In an ongoing effort to study the environmental fate of endocrine-active steroid hormones, we report the formation of phenolic rearrangement products (3 and 4) with a novel 6,5,8,5-ring system following aqueous photolysis of dienogest (1) and methyldienolone (2). The structures were established by analysis of 2D NMR and HRMS data, and that of 3 was confirmed by X-ray diffraction analysis. These photoproducts exhibit progestogenic and androgenic activity, albeit with less potency than their parent compounds.
Topics: Molecular Structure; Nandrolone; Pharmaceutical Preparations; Photolysis; Steroids
PubMed: 31021644
DOI: 10.1021/acs.orglett.9b00972 -
Molecules (Basel, Switzerland) Aug 2018Ultra-violet (UV) irradiation has a significant impact on the structure and function of proteins that is supposed to be in relationship with the tryptophan-mediated...
Ultra-violet (UV) irradiation has a significant impact on the structure and function of proteins that is supposed to be in relationship with the tryptophan-mediated photolysis of disulfide bonds. To investigate the correlation between the photoexcitation of Trp residues in polypeptides and the associated reduction of disulfide bridges, a series of small, cyclic oligopeptide models were analyzed in this work. Average distances between the aromatic side chains and the disulfide bridge were determined following molecular mechanics (MM) geometry optimizations. In this way, the possibility of cation⁻π interactions was also investigated. Molecular mechanics calculations revealed that the shortest distance between the side chain of the Trp residues and the disulfide bridge is approximately 5 Å in the cyclic pentapeptide models. Based on this, three tryptophan-containing cyclopeptide models were synthesized and analyzed by nuclear magnetic resonance (NMR) spectroscopy. Experimental data and detailed molecular dynamics (MD) simulations were in good agreement with MM geometry calculations. Selected model peptides were subjected to photolytic degradation to study the correlation of structural features and the photolytic cleavage of disulfide bonds in solution. Formation of free sulfhydryl groups upon illumination with near UV light was monitored by fluorescence spectroscopy after chemical derivatization with 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) and mass spectrometry. Liquid cromatography-mass spectrometry (LC-MS) measurements indicated the presence of multiple photooxidation products (e.g., dimers, multimers and other oxidated products), suggesting that besides the photolysis of disulfide bonds secondary photolytic processes take place.
Topics: Chromatography, Liquid; Dimethyl Sulfoxide; Hydrogen Bonding; Light; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Dynamics Simulation; Molecular Structure; Peptides, Cyclic; Photochemical Processes; Photolysis; Spectrometry, Fluorescence; Ultraviolet Rays
PubMed: 30200264
DOI: 10.3390/molecules23092196