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We report a mechanistic investigation of an aromatic dithioimide (2SS) displaying puzzling yet efficient photochemistry in ether solvents. Perplexingly, 2SS dissolved in ether solvents in a sealed and degassed vial was photochemically converted to the corresponding diimide (2OO), as determined by 1H NMR following product extraction. With no external sources of oxygen in the sample, could the oxygen in 2OO be from the ether itself? To study this unprecedented proposition, we attempt to uncover the ether's involvement in this reaction. As seen by laser‐flash photolysis, 2SS appears to first react with the solvent from its singlet excited state. Following the reaction by NMR under rigorously oxygen‐ and water‐free conditions led to the identification of a photoreductive pathway that quantitatively transformed one thione into a methylene to yield 2SH2. Subsequent oxidation of 2SH2 or irradiation of 2SS under air proved that molecular oxygen was indeed necessary to observe an oxidative pathway leading to 2OO, ruling out the initially proposed involvement of an ether oxygen. An explanation of 2SS desulfurization was further revealed through the study of solvent by‐products by GC‐MS analysis. Supported by DFT calculations, a mechanism is proposed to involve a chain reaction initiated by photochemically generated ether radical. [ABSTRACT FROM AUTHOR]

The present study focuses on the effects of the physicochemical properties of superparamagnetic PEG-modified, positively charged, and negatively charged iron oxide nanoparticles (SPIONs) on their reactivity with hydrogen peroxide. Our hypothesis was that the reactivity of SPIONs in this reaction would depend on their surface properties. The comparative study of the nanoparticles with DLS and TEM revealed the average sizes of PEG-modified, positively charged, and negatively charged SPIONs. We observed that the reactivity of negatively charged SPIONs with hydrogen peroxide was less than that of positively charged SPIONs and that of these second nanoparticles was less than that of PEG-modified SPIONs. This difference in the reactivity of these SPIONs with hydrogen peroxide was attributed to the presence of carboxyl or amine groups on their surface. However, the values of the rate constants of the reactions of PEG-modified, positively charged, and negatively charged SPIONs with hydrogen peroxide showed that the reaction of negatively charged SPIONs with hydrogen peroxide was more rapid than that of PEG-modified SPIONs and the reaction of these second SPIONs with hydrogen peroxide was more rapid than that of positively charged SPIONs. The surface study of the SPIONs using XPS showed that the high-resolution spectra of these nanoparticles changed after reaction with hydrogen peroxide, which indicates their surface modifications. These investigations can help develop more appropriate nanoparticles with controlled physicochemical properties. Key words: superparamagnetic iron oxide nanoparticles, FTIR, DLS, SEM, XPS, oxygen uptake. La presente etude porte sur les effets des proprietes physicochimiques de nanoparticules d'oxyde de fer superparamagetique (SPION, acronyme anglais pour superparamagnetic iron oxide nanoparticles) soit modifiees par le polyethylèneglycol (PEG), chargees positivement ou chargees negativement sur leur reactivite face au peroxyde d'hydrogène. Nous avions pose l'hypothèse que la reactivite des SPIONs dans cette reaction devrait dependre de leurs proprietes de surface. L'etude comparative de ces nanoparticules par diffusion dynamique de la lumière (DDL) et microscopie electronique en transmission (MET) a permis de determiner la taille moyenne des SPIONs modifiees par le PEG, chargees positivement et chargees negativement. Nous avons observe que la reactivite des SPIONs chargees negativement à l'egard du peroxyde d'hydrogène etait moindre que celle des SPIONs chargees positivement, et que celle de ces dernières nanoparticules etait moindre que celle des SPIONs modifiees par le PEG. Nous avons attribue cette difference de reactivite entre ces SPION à l'egard du peroxyde d'hydrogène à la presence de groupes carboxyle et amine à leur surface. Cependant, les valeurs de la constante de vitesse des reactions des SPION-PEGs, des SPIONs chargees positivement et des SPIONs chargees negativement avec le peroxyde d'hydrogène ont montre que la reaction des SPIONs chargees negativement avec le peroxyde d'hydrogène etait plus rapide que celle des SPION-PEGs et que la reaction de ces dernières avec le peroxyde d'hydrogène etait plus rapide que celle des SPIONs chargees positivement. L'etude de surface des SPIONs à l'aide de la spectroscopie de photoelectrons X (XPS) a montre que les spectres à haute resolution de ces nanoparticules avaient change après la reaction avec le peroxyde d'hydrogène, ce qui est revelateur de modifications de la surface. Ces recherches pourront permettre la mise au point de nanoparticules plus appropriees aux proprietes physicochimiques modulables. [Traduit par la Redaction] Mots-cles : nanoparticules d'oxyde de fer superparamagnetique, FTIR, DDL, MEB, XPS, consommation d'oxygène., Introduction The surface modification of nanoparticles (NPs) has attracted significant interest over the last decades. NPs consist of a core and shell with dimensions of 1-100 nm that result in [...]

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Acid-catalyzed deprotection of tert-butoxycarbonyl (t-Boc) pendant groups present in a polymer film is one of the most common chemical reactions in photolithography. We present here a novel method to determine the catalytic chain length of this reaction under different development conditions. We demonstrate this in model PMMA thin films containing triphenylsulphonium triflate as a photoacid generator, acid sensor coumarin 6, t-Boa protected coumarin 4, and base 2-piperidin-l-yl-ethanol (2-PE). Deprotection of the t-Boa group, catalyzed by the photogenerated acid, during the post-exposure bake leads to formation of coumarin 4, a strongly fluorescent molecule whose concentration is monitored using fluorescence. We take advantage of the change in the emission spectra of coumarin 6 upon protonation to monitor acid formation. To quantify the amount of acid, an acid-base titration is done in the polymer film using 2-PE. Knowing the amount of deprotected probe and the amount of acid, we are able to calculate the number of moles of deprotected C4-t-Boc per mol of acid, which is the actual catalytic chain length. Key words: photolithography, chemical amplification, catalytic chain length, fluorescent sensors, photoacid generator. La deprotection acidocatalysee des groupes pendants tert-butoxycarbonyles (t-Boc) presents dans un film de polymere est une des reactions chimiques les plus communes en photolithographie. Dans ce travail, on presente une nouvelle methode pour determiner la longueur de la chaine catalytique de cette reaction dans diverses conditions de developpement. Ceci est demontre dans des films minces modeles de PMMA contenant du triflate de triphenylsulfonium comme generateur photoacide, le detecteur d'acide coumarine 6, la coumarine 4 portant un groupe protecteur t-Boc et la base 2-piperidin-l-yl-ethanol (2-PE). La deprotection du groupe t-Boc, catalysee par l'acide photogenere au cours de la cuisson suivant l'exposition, conduit a la formation de la coumarine 4, une molecule fortement fluorescente dont on peut determiner la concentration par fluorescence. On tire avantage du changement dans le spectre d'emission de la coumarine 6 lors de la protonation pour deceler la formation d'acide. Afin de quantifier la quantite d'acide, on realise un titrage acide-base dans le film de polymere a l'aide du 2-PE. Connaissant la quantite de sonde deprotonee et la quantite d'acide, il est possible de calculer le nombre de moles de C4-t-Boc deprotege par mol d'acide, ce qui correspond a la longueur de la chaine catalytique. Mots cles : photolithographie, amplification chimique, longueur d'une chaine catalytique, detecteurs fluorescents, generateur photoacide. [Traduit par la Redaction]

The photophysical and electrochemical properties for a series of BODIPY dyes with incremental 3‐ and 3,5‐vinyl conjugation, as well as incremental electron‐donating groups (anisole < triphenylamine < ferrocenyl), are presented. Insight into the influence of each vinyl‐conjugated electron‐donating group on both vis‐NIR absorption and fluorescence emission properties is provided. These trends are further corroborated by density functional theory computational analysis. Two of this series containing the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituents exhibit significant absorption cross sections in the biological transparency window justifying further investigation of their photoacoustic emission properties via both optical photoacoustic z‐scan and photoacoustic tomography experiments. Both the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituted BODIPY dyes exhibit quantitative photoacoustic quantum yields. Relative to the commercially available methylene blue and indocyanine green molecular photoacoustic contrast agents, the 3,5‐bis(vinyltriphenylamine)‐derived BODIPY exhibits the greatest photoacoustic emission and contrast upon excited‐state absorption at 685 nm excitation at a low power laser fluence (<20 mJ cm‐2). [ABSTRACT FROM AUTHOR]

The photophysical and electrochemical properties for a series of BODIPY dyes with incremental 3‐ and 3,5‐vinyl conjugation, as well as incremental electron‐donating groups (anisole < triphenylamine < ferrocenyl), are presented. Insight into the influence of each vinyl‐conjugated electron‐donating group on both vis‐NIR absorption and fluorescence emission properties is provided. These trends are further corroborated by density functional theory computational analysis. Two of this series containing the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituents exhibit significant absorption cross sections in the biological transparency window justifying further investigation of their photoacoustic emission properties via both optical photoacoustic z‐scan and photoacoustic tomography experiments. Both the 3,5‐bis(vinyltriphenylamine) and 3,5‐bis(vinylferrocenyl) substituted BODIPY dyes exhibit quantitative photoacoustic quantum yields. Relative to the commercially available methylene blue and indocyanine green molecular photoacoustic contrast agents, the 3,5‐bis(vinyltriphenylamine)‐derived BODIPY exhibits the greatest photoacoustic emission and contrast upon excited‐state absorption at 685 nm excitation at a low power laser fluence (<20 mJ cm‐2). [ABSTRACT FROM AUTHOR]

The photocatalytic hydroboration of alkenes and alkynes is reported. The use of newly‐designed copper photocatalysts with B2Pin2 permits the formation a boryl radical, which is used for hydroboration of a large panel of alkenes and alkynes. The hydroborated products were isolated in high yields, with excellent diastereoselectivities and a high functional group tolerance under mild conditions. The hydroboration reactions were developed under continuous flow conditions to demonstrate their synthetic utility. The reaction mechanism was studied and suggested an oxidation reaction between an in situ formed borate and the Cu‐photocatalyst in its excited state for the boryl radical formation. [ABSTRACT FROM AUTHOR]

We report detailed mechanistic investigations of an iron‐based catalyst system, which allows the α‐C−H oxidation of a wide variety of amines. In contrast to other catalysts that effect α‐C−H oxidations of tertiary amines, the system under investigation exclusively employs peroxy esters as oxidants. More common oxidants (e. g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α‐C−H oxidation products in combination with the described catalyst system. The investigations described herein employ initial rate kinetics, kinetic profiling, DFT calculations as well as Eyring, kinetic isotope effect, Hammett, ligand coordination, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C−H abstraction at a coordinated substrate molecule. This rate‐determining step occurs either through an Fe(IV) oxo pathway or a 2‐electron pathway at an Fe(II) intermediate with bound oxidant. DFT calculations indicate that the Fe(IV) oxo mechanism will be the preferred route of these two possibilities. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3tBu to tBuOOH. Overall, the obtained mechanistic data support a non‐classical, Fe catalyzed pathway that requires substrate binding, inducing selectivity for α‐C−H functionalization. [ABSTRACT FROM AUTHOR]

Evidence is provided for the formation of hydroxyl radicals during lipid peroxidation, a common process associated with oxidative stress. The [alpha]C-H hydrogen abstraction from hydroperoxides formed during lipid autooxidation has led to the formation of ketones and hydroxyl radicals.

A new class of thermally activated chain-breaking antioxidants based on a radical-dimer equilibrium is discovered. It is shown that these dimers can prevent autoxidation in model systems by trapping peroxyl radicals very efficiently, even at temperatures as low as 30 degrees Celsius.

The synthesis and characterization of a series of donor-π-acceptor-π-donor (D-A-D) curcuminoid molecules is presented herein that incorporates π-extended aryl and electron-donating amino terminal functionalization. Computational evaluation shows these molecules possess quadrupolar character with the lowest energy transitions displaying high molar extinction coefficients with broad tunability through manipulation of terminal donating groups. Consistent with their quadrupolar nature, these molecules show varying degrees of solvatochromic behavior in both their absorption and emission spectra, which has been analyzed by Lippert-Mataga and Kamlet-Taft analysis. Photophysical and photoacoustic (PA) properties of these molecules have been investigated by the optical photoacoustic z-scan (OPAZ) method. Selected curcuminoid molecules display nonlinear behavior at a high laser fluence through excited state absorption that translates to the production of an enhanced photoacoustic emission. A relative comparison of "molar PA emission" is also presented with the crystal violet linear optical absorbing/linear PA emitting system being utilized as a standard reference material for OPAZ experiments. Furthermore, PA tomography experiments are presented to illustrate the enhanced PA contrast obtainable via an excited state absorption. [ABSTRACT FROM AUTHOR]

A visible-light-driven Minisci protocol that employs an inexpensive earth-abundant metal catalyst, decacarbonyldimanganese Mn2(CO)10, to generate alkyl radicals from alkyl iodides has been developed. This Minisci protocol is compatible with a wide array of sensitive functional groups, including oxetanes, sugar moieties, azetidines, tert-butyl carbamates (Boc-group), cyclobutanes, and spirocycles. The robustness of this protocol is demonstrated on the late-stage functionalization of complex nitrogen-containing drugs. Photophysical and DFT studies indicate a light-initiated chain reaction mechanism propagated by .Mn(CO)5. The rate-limiting step is the iodine abstraction from an alkyl iodide by .Mn(CO)5. [ABSTRACT FROM AUTHOR]

A visible-light-promoted iridium photoredox and nickel dual-catalyzed cross-coupling procedure for the formation C−N bonds has been developed. With this method, various aryl amines were chemoselectively cross-coupled with electronically and sterically diverse aryl iodides and bromides to forge the corresponding C−N bonds, which are of high interest to the pharmaceutical industries. Aryl iodides were found to be a more efficient electrophilic coupling partner. The coupling reactions were carried out at room temperature without the rigorous exclusion of molecular oxygen, thus making this newly developed Ir-photoredox/Ni dual-catalyzed procedure very mild and operationally simple. [ABSTRACT FROM AUTHOR]

Ni-catalyzed cross-couplings of aryl, benzyl, and alkyl thiols with aryl and heteroaryl iodides were accomplished in the presence of an Ir-photoredox catalyst. Highly chemoselective C-S cross-coupling was achieved versus competitive C-O and C-N cross-couplings. This C-S cross-coupling method exhibits remarkable functional group tolerance, and the reactions can be carried out in the presence of molecular oxygen. Mechanistic investigations indicated that the reaction proceeded through transient Ni(I)-species and thiyl radicals. Distinct from nickel-catalyzed cross-coupling reactions involving carbon-centered radicals, control experiments and spectroscopic studies suggest that this C-S cross-coupling reaction does not involve a Ni(0)-species. [ABSTRACT FROM AUTHOR]

A first approach toward understanding the targeted design of molecular photoacoustic contrast agents (MPACs) is presented. Optical and photoacoustic Z-scan spectroscopy was used to identify how nonlinear (excitedstate) absorption contributes to enhancing the photoacoustic emission of the curcuminBF2 and bis-styryl (MeOPh)2BODIPY dyes relative to Cy3. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of a series of pyrrolic compounds consisting of BODIPY and aza-BODIPY systems are investigated using 532 nm nanosecond laser and the Z-scan technique. Results show that 3,5-distyryl extension of BODIPY to the red shifted MeO2BODIPY dye has a dramatic impact on its nonlinear absorption properties changing it from a saturable absorber to an efficient reverse saturable absorbing material with a nonlinear absorption coefficient of 4.64x10-10m/W. When plotted on a concentration scale per mole of dye in solution MeO2BODIPY far outperforms the recognized zinc(II) phthalocyanine dye and is comparable to that of zinc(II) tetraphenylporphyrin. [ABSTRACT FROM AUTHOR]

Purpose To describe the fabrication, evaluation, and preliminary in vivo safety of a new drug delivery system (DDS) for topical anti–TNF-α antibody administration. Methods: A DDS was fabricated using inverse template fabrication of a hydrophobic three-dimensional porous scaffold (100–300 μm in diameter porosity) loaded with 10% polyvinyl alcohol hydrogel carrying 5 mg/ml (weight/volume) of anti–TNF-α antibody. Drug-loaded DDS was sterilized with 25 kGy of gamma irradiation. Long-term in vitro antibody affinity and release was evaluated at room temperature or 37°C using enzyme-linked immunosorbent assay (ELISA) and protein fluorescence. In vivo clinical and histolopathological assessment was performed by subcutaneous implantation in BALB/c mice for 3 months. Results: Gamma irradiation, repeated dry/wet cycles, and storage at room temperature for 1 year or 37°C for 1 month had no deleterious effects on antibody affinity. Anti–TNF-α release was high during the first minutes of aqueous exposure, followed by stabilization and gradual, low-dose, antibody release over the next 30 days. Histopathologic evaluation of explanted DDS showed a fibrous pseudocapsule and a myxoid acute/chronic inflammation without granuloma formation surrounding the implants. Conclusions: Sustained local delivery of anti–TNF-α antibody is feasible using the described DDS, which provides stability of the enclosed antibody for up to 1 year of storage. Preliminary results show good in vivo tolerance following subcutaneous placement for 3 months. The proposed fabrication and sterilization process opens new possibilities for the delivery of biologic agents to the anterior surface of the eye. Translational Relevance The described DDS will facilitate the treatment of ocular surface diseases amenable to biologic therapy.

We demonstrate the application of solid-state fluorescence spectroscopy for the real-time monitoring and characterisation of solid forms (e.g. polymorphs, solvates, cocrystals) of pharmaceutical molecules. This proof-of-principle study focuses on the pharmaceutical indomethacin which, although poorly fluorescent in solution, in the solid state yields highly fluorescent amorphous, polymorphic, solvate and cocrystal forms. We show that solid forms of indomethacin can be readily distinguished by their fluorescent properties and, by using a simple and readily available experimental set-up, we reveal that fluorescence spectroscopy can be used to quantify amorphous and crystalline forms in a mixture and to monitor the kinetics of their interconversion in situ and in real-time (30 seconds resolution or less). [ABSTRACT FROM AUTHOR]

Cover Feature: Mechanistic Insights into Fe Catalyzed -C-H Oxidations of Tertiary Amines (ChemCatChem 1/2021) Keywords: Iron catalysis; C-H oxidation; kinetics; DFT calculation; mechanistic analysis EN Iron catalysis C-H oxidation kinetics DFT calculation mechanistic analysis 4 4 1 01/18/21 20210112 NES 210112 B The Cover Feature b shows cast iron catalysis: Trialkyl amines cooked with the right recipe will take the oxygen from water to form the corresponding trialkyl amide. Iron catalysis, C-H oxidation, kinetics, DFT calculation, mechanistic analysis. [Extracted from the article]

Interaction of 7-mercapto-4-methylcoumarin with the surface of core–shell CdSe–ZnS quantum dots leads to characteristic absorption and emission bands that are excellent reporters for thiol interactions at the nanoparticle surface. [ABSTRACT FROM AUTHOR]

The cover page of the journal "Angewandte Chemie" is presented.

Die Rädchen von Ir ‐ Photoredox ‐ und Ni ‐ Katalyse …… greifen ineinander und erzeugen eine leistungsstarke Kreuzkupplungsmaschinerie. M. S. Oderinde, J W. Johannes et al. beschreiben in ihrer Zuschrift auf S. 13413 ff. Arylaminierungen mit einem solchen dualen Katalysatorsystem unter Bestrahlung mit einer blauen LED. Die Doppelfunktion des Ir ‐ Komplexes in der Oxidation der Arylamine und der Reduktion von NiII über Außensphären ‐ Einelektronentransfer ermöglicht C ‐ N ‐ Kreuzkupplungen unter erstaunlich milden Bedingungen. [ABSTRACT FROM AUTHOR]

Highly chemoselective photoinduced Ni-catalyzed cross-coupling reactions of aryl, benzyl, and alkyl thiols with aryl and heteroaryl iodides in the presence of an Ir(III)-photoredox catalyst are developed. [ABSTRACT FROM AUTHOR]