Showing papers on "Benzophenone published in 2021"

New multifunctional benzophenone-based photoinitiators with high migration stability and their applications in 3D printing

Abstract: In this paper, seven new photoinitiators based on the benzophenone scaffold are specifically designed for photopolymerization under mild conditions upon light-emitting diode (LED) irradiation, i.e. four benzophenone-triphenylamine photoinitiators (denoted as BT1–BT4) and three benzophenone-carbazole photoinitiators (denoted as BC1–BC3). Noticeably, these structures have never been reported in the literature except for BT4, so these molecules have been specifically designed for photopolymerization applications. Remarkably, various combinations of chemical groups were investigated in this work to determine the effects of the substitution patterns on their photoinitiation abilities. The formation of benzophenone-triphenylamine and benzophenone-carbazole hybrid structures not only contributes to red-shift of the absorption maxima but also strongly enhances their molar extinction coefficients. The different compounds showed high photoinitiation abilities upon irradiation with an LED@405 nm, and the free radical photopolymerization of acrylates and the cationic polymerization of epoxides could be promoted with high final function conversions (e.g. 77% for the BT3/iodonium salt/amine system in free radical photopolymerization). Remarkably, these new PIs are also able to sensitize sulfonium salts upon irradiation @405 nm. Markedly, because of the benzophenone moiety, a monocomponent Type II PI behavior could be observed, e.g. these compounds could initiate the polymerization alone. Remarkably, benzophenone-triphenylamine compounds BT2, BT3 and BT4 exhibited better hydrogen abstraction abilities as Type II photoinitiators than the benchmark and commercial photoinitiator 2-isopropylthioxanthone in the absence of amines as well as in the presence of amines. Furthermore, the interaction between the photoinitiators and the different additives was investigated by steady state photolysis and fluorescence quenching experiments. The free radical generation in the BT3/amine system was confirmed by the electron spin resonance-spin trapping technique, and the chemical mechanisms related to the polymerization efficiency are discussed. In addition, the migration stability of BT3 was investigated, which was excellent due to its high molecular weight and its trifunctional character. Finally, the three-component photoinitiating system based on BT3 was successfully applied in 3D printing and the 3D patterns showed a good spatial resolution.

Benzophenone Accumulates over Time from the Degradation of Octocrylene in Commercial Sunscreen Products

Abstract: Benzophenone is a mutagen, carcinogen, and endocrine disruptor. Its presence in food products or food packaging is banned in the United States. Under California Proposition 65, there is no safe harbor for benzophenone in any personal care products, including sunscreens, anti-aging creams, and moisturizers. The purpose of this study was to determine (1) if benzophenone was present in a wide variety of commercial sun protection factor (SPF)/sunscreen products, (2) whether benzophenone concentration in the product increased over time, and (3) if the degradation of octocrylene was the likely source for benzophenone contamination. Benzophenone concentration was assayed in nine commercial sunscreen products from the European Union and eight from the United States (in triplicate), including two single ingredient sources of octocrylene. These same SPF items were subjected to the United States Food and Drug Administration (U.S. FDA)-accelerated stability aging protocol for 6 weeks. Benzophenone was measured in the accelerated-aged products. Sixteen octocrylene-containing product lines that were recently purchased had an average concentration of 39 mg/kg benzophenone, ranging from 6 mg/kg to 186 mg/kg. Benzophenone was not detectable in the product that did not contain octocrylene. After subjecting the 17 products to the U.S. FDA-accelerated stability method, the 16 octocrylene-containing products had an average concentration of 75 mg/kg, ranging from 9.8 mg/kg to 435 mg/kg. Benzophenone was not detectable in the product that did not contain octocrylene. Benzophenone was detected in the pure octocrylene manufactured ingredient. Octocrylene generates benzophenone through a retro-aldol condensation. In vivo, up to 70% of the benzophenone in these sunscreen products may be absorbed through the skin. U.S. FDA has established a zero tolerance for benzophenone as a food additive. In the United States, there were 2999 SPF products containing octocrylene in 2019. The safety of octocrylene as a benzophenone generator in SPF or any consumer products should be expeditiously reviewed by regulatory agencies.

A Copper-Containing Polyoxometalate-Based Metal-Organic Framework as an Efficient Catalyst for Selective Catalytic Oxidation of Alkylbenzenes.

Abstract: A copper-containing polyoxometalate-based metal-organic framework (POMOF), CuI12Cl2(trz)8[HPW12O40] (HENU-7, HENU = Henan University; trz = 1,2,4-triazole), has been successfully synthesized and well-characterized. In addition, the excellent catalytic ability of HENU-7 has been proved by the selective oxidation of diphenylmethane. Under the optimal conditions, the diphenylmethane conversion obtained over HENU-7 is 96%, while the selectivity to benzophenone is 99%, which outperforms most noble-metal-free POM-based catalysts. Moreover, HENU-7 is stable to reuse for five runs without an obvious loss in activity and also can catalyze the oxidation of different benzylic C-H with satisfactory conversions and selectivities, which implied the significant catalytic activity and recyclability.

Novel A-π-D-π-A structure two-photon polymerization initiators based on phenothiazine and carbazole derivatives

Abstract: Two-photon polymerization additive manufacturing has great demand for new and efficient two-photon initiators. Acetylene bridged A-π-D-π-A initiator molecules based on phenothiazine and carbazole were designed and synthesized via Sonogashira coupling reaction utilizing benzophenone and fluorenone as electron-donating groups. The ultraviolet-visible absorption spectra, fluorescence emission spectra, two-photon absorption cross section, two-photon fluorescence properties, as well as their photoinitiation properties as initiators, were studied. The results showed that different electron donors and acceptors directly affect the photophysical properties of molecules, and their effects are interrelated. Among them, under the action of femtosecond laser, the two-photon absorption cross section of the molecule with phenothiazine as the donor and benzophenone as the acceptor can reach 327 GM at 780 nm. Two-photon polymerization experiments have also proved that it can indeed initiate trimethylolpropane triacrylate photopolymerization for micro-/nano-manufacturing. The scanning rate reached 2000 μm s−1 at a laser power of 30 mW during the polymerization process, and the complete and clear three-dimensional structures were obtained. The highest resolution of the complete three-dimensional structure was about 280 nm.

Unlocking the Water Trimer Loop: Isotopic Study of Benzophenone‐(H2O)1‐3 Clusters with Rotational Spectroscopy

Abstract: Examined here are the structures of complexes of benzophenone microsolvated with up to three water molecules by using broadband rotational spectroscopy and the cold conditions of a molecular jet. The analysis shows that the water molecules dock sideways on benzophenone for the water monomer and dimer moieties, and they move above one of the aromatic rings when the water cluster grows to the trimer. The rotational spectra shows that the water trimer moiety in the complex adopts an open-loop arrangement. Ab initio calculations face a dilemma of identifying the global minimum between the open loop and the closed loop, which is only solved when zero-point vibrational energy correction is applied. An OH⋅⋅⋅π bond and a Burgi-Dunitz interaction between benzophenone and the water trimer are present in the cluster. This work shows the subtle balance between water-water and water-solute interactions when the solute molecule offers several different anchor sites for water molecules.

Theoretical Determination of Rate Constants from Excited States: Application to Benzophenone.

Abstract: A cost-effective method of theoretically predicting electronic-transition rate constants from the excited states of molecules is reported. This method is based on density functional theory calculations of electronic states and quantitative rate constant determination with the Fermi golden rule. The method is applied to the theoretical determination of the excited-state decay mechanism of photoexcited benzophenone, a representative molecule in photochemistry and biochemistry. Calculated rate constants for benzophenone are quantitatively consistent with experimental ones, which validates the reliability of our rate constant calculation. The calculated population kinetics indicate that S1 → T2 → T1 → S0 is the predominant decay pathway.

Electrochemical Oxidative C(sp3)-H/N-H Coupling of Diarylmethanes with Sulfoximines or Benzophenone Imine.

Abstract: Herein, we report an efficient electrochemical method for the synthesis of N-alkylated sulfoximines by electrochemical oxidative C(sp3)-H/N-H coupling of sulfoximines and diarylmethanes. In addition, we used the same conditions for electrochemical dehydrogenative amination of diarylmethanes with benzophenone imine as an aminating agent. The reactions showed good functional group tolerance and afforded the corresponding products in moderate to good yields without the use of a stoichiometric oxidant, a metal catalyst, or an activating agent.

Effects of molecular architecture of photoreactive phospholipid polymer on adsorption and reaction on substrate surface under aqueous condition.

Abstract: Water-soluble photoreactive polymers with both phosphorylcholine and benzophenone groups were synthesized for the reaction between the polymers and the substrate in aqueous medium. To control the polymer architecture, the living radical polymerization method was applied to the copolymerization of 2-methacryloyloxyethyl phosphorylcholine and benzophenone methacrylates. These polymers possess various architectures, such as linear polymers, polymers with hydrophobic terminals, and 4-armed star-like polymers, that could promote their adsorption on the substrate surfaces. Additionally, two types of benzophenone groups were examined. Due to the bulky phosphorylcholine group, tetra(ethylene oxide) group as a spacer between polymer main chain and benzophenone group was considered. These polymers could adsorb on the surface in an aqueous medium, followed by reaction on the surface via photoirradiation depending on the chemical structure of the benzophenone group. The thickness of the polymer layer depended on the polymer architecture, i.e. a polymer with a hydrophobic terminal could form a thick layer. After modification, the contact angle by air in the aqueous medium decreased, compared to that on the base substrate. This was due to the hydrophilic nature based on the phosphorylcholine groups at the surface. The amount of proteins adsorbed on the surface also decreased because of the surface modification. These findings indicated that these water-soluble photoreactive polymers could be applied for the safer and effective surface modification of substrates via conventional photoirradiation without using an organic solvent.

Determination of Photoinduced Radical Generation Quantum Efficiencies by Combining Chemical Actinometry and 19F NMR Spectroscopy

Abstract: We introduce a general and relatively straightforward protocol aimed at determining the absolute photoinduced radical generation efficiency via NMR monitoring. This approach relies on the use of a radical scavenger probe that combines a nitroxide moiety that specifically reacts with radicals and a trifluoromethyl group used as a 19F NMR signaling unit. Using an LED source, whose fluence is precisely determined by a chemical actinometry procedure also described herein, the method is used to determine the radical photogeneration quantum yields of three well-known polymerization initiators: azobisisobutyronitrile (AIBN), 4,4'-bis(N,N-diethylamino)benzophenone (BDEBP, a derivative of Michler's ethyl ketone), and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (MAPO). The overall good agreement with values previously reported in the literature proves the robustness of this new method. We then extended the study to the precise measurement of the quantum yield of free-radical photogeneration on a newly synthesized photoinitiator used for two-photon direct laser writing. This study highlights the potential of this methodology for the quantitative determination of photoinduced radical generation efficiency used in many fields of applications.

Ketone Number and Substitution Effect of Benzophenone Derivatives on the Free Radical Photopolymerization of Visible-Light Type-II Photoinitiators.

Abstract: Three novel visible-light absorbing benzophenone-based hydrogen acceptors (BPD-D, BPDM-D and BPDP-D) were designed on the basis of a donor-benzophenone-donor structural backbone. Mono or diketone units and double diphenylamine electron-donating groups in para-or meta-positions were introduced to comprehend the electronic and structural effects on free radical photopolymerization (FRPP). Such a structural change leads not only to a red-shift of the absorption maxima but strongly enhances their molar extinction coefficients compared to the commercial phototinitiators such as benzophenone (BP) and 4,4'-bis(diethylamino) benzophenone (EMK). In addition, excellent melting points and thermal decomposition temperatures were achieved for those novel compounds. Further, the photochemical reaction behavior was studied by cyclic voltammograms (CV), photolysis and electron spin resonance (ESR) spectroscopy. Finally, benzophenone derivatives in combination with an amine (TEA, triethylamine) as a co-initiator were prepared and initiated the FRPP of trimethylolpropane trimethacrylate (TMPTMA) using a UV lamp as a light source. When used in stoichiometric amounts, the BPDP-D/TEA had the best double bond conversion efficiency among all the compounds studied, and were even superior to the reference compounds of BP/TEA and EMK/TEA. The results and conclusions could provide the fundamental rules applicable for the structural design of benzophenone derivative-based photoinitiators.

Sulphate radical oxidation of benzophenone: kinetics, mechanisms and influence of water matrix anions

Abstract: Benzophenone (BP) is an emerging contaminant that is widely distributed in soil, groundwater, sediment and surface water. In this study, the degradation kinetics, mechanisms, and influence of anion...

Design, Synthesis and Antimicrobial Activity Evaluation of New Bisimidyl Sulfonamido Ketone Comprising Drug component

Abstract: This work involved design and synthesis of four new compounds which their molecules contain three biologically active segments, including β-lactam containing drug, cyclic imide and sulfonamido group. Synthesis of the compounds was performed by several steps. In the first step, compound (1) bis[N-phenyl phthalamic acid] ketone was synthesized via reaction of aniline with benzophenone 3,3’,4,4’-tetra carboxylic dianhydride. In the second step, compound (1) was dehydrated by fusion to give the corresponding bis phthalimide (2) which in turn was introduced in reaction with chloro sulfonic acid. The third step involved producing compound (3), the corresponding bis phthalimidyl benzene sulfonyl chloride. Compound (3) is the important key compound from which the target compounds (4-7) were prepared through its reaction with different β-lactam containing drugs. Antibacterial and antifungal activities of compounds (4-7) were screened and the results indicated that they have high biological activity.

Raman Spectra of Persistent Radical Anions from Benzophenone, Fluorenone, 2,2'-Bipyridyl, 4,4'-Di-tert-butyl-2,2'-dipyridyl, and Anthracene: Excellent Agreement between DFT and Experiment for Highly Delocalized Radical Systems.

Abstract: We report detailed Raman spectra for the neutral and radical anion forms of benzophenone, fluorenone, 2,2'-bipyridyl, 4,4'-di-tert-butyl-2,2'-dipyridyl, and anthracene. Density functional theory (DFT) predictions for the Raman spectra of these molecules give additional insight into the assignment of each vibrational mode. While the use of DFT has been problematic in quantifying the thermochemistry of highly delocalized radicals, we find that DFT-predicted spectra using the popular B3LYP functional are in excellent agreement with the observed Raman spectra. In the case of the two bipyridyl compounds, the Raman spectra allowed us to conclude that the cis form of the radical anion complexed to a sodium cation was the preferred configuration. Benzophenone and fluorenone radical anions gave a significantly weakened C═O bond stretching vibrational frequency as expected from the population of an antibonding π* orbital. For benzophenone, the C═O vibration dropped from 1659 to 1403 cm-1 upon reduction. Similarly, fluorenone showed a C═O vibration observed at 1719 cm-1 for the neutral form that decreased to 1522 cm-1 for the radical anion. The structurally rigid anthracene showed relatively smaller Raman band shifts upon single-electron reduction as the π* orbital is more equally delocalized on the entire structure. In total, we correlated 65 DFT-predicted vibrational modes for the neutral molecules with an overall error of 7.1 cm-1 (root-mean-square errors (RMSEs)) and 67 DFT-predicted vibrational modes for radical anions with an overall error of 9.9 cm-1. These comparisons between theory and experiment are another example to demonstrate the power of DFT in predicting the identity and geometry of molecules using Raman spectroscopy.

In Situ Monitoring of a Quasi Solid-State Diffusion-Driven Cocrystallization in the Diphenylamine–Benzophenone System

Abstract: Diphenylamine reacts with benzophenone in the solid state through the formation of a eutectic liquid intermediate, from which the final product, in the form of a hydrogen-bonded cocrystal, is final...