TY - JOUR A1 - Krüger, Tobias A1 - Linker, Torsten T1 - Synthesis of gamma-spirolactams by Birch reduction of arenes JF - European journal of organic chemistry N2 - A convenient method for the synthesis of gamma-spirolactams in only three steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of chloroacetonitrile affords nitriles in moderate to good yields. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and anthroic acid. Subsequent catalytic hydrogenation proceeds smoothly with PtO2 or Raney Ni as catalysts and lactams are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation at different pressures, affording products with 0, 1, or 2 double bonds. Overall, more than 15 new gamma-spirolactams have been synthesized in analytically pure form. KW - Arenes KW - Birch reduction KW - Hydrogenation KW - Lactams KW - Synthetic methods Y1 - 2021 U6 - https://doi.org/10.1002/ejoc.202100056 SN - 1099-0690 VL - 2021 IS - 10 SP - 1585 EP - 1591 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Fudickar, Werner A1 - Metz, Melanie A1 - Mai-Linde, Yasemin A1 - Krüger, Tobias A1 - Kelling, Alexandra A1 - Sperlich, Eric A1 - Linker, Torsten T1 - Influence of functional groups on the ene reaction of singlet oxygen with 1,4-cyclohexadienes JF - Photochemistry and photobiology : the official journal of the American Society for Photobiology N2 - The photooxygenation of 1,4-cyclohexadienes has been studied with a special focus on regio- and stereoselectivities. In all examples, only the methyl-substituted double bond undergoes an ene reaction with singlet oxygen, to afford hydroperoxides in moderate to good yields. We explain the high regioselectivities by a "large-group effect" of the adjacent quaternary stereocenter. Nitriles decrease the reactivity of singlet oxygen, presumably by quenching, but can stabilize proposed per-epoxide intermediates by polar interactions resulting in different stereoselectivities. Spiro lactams and lactones show an interesting effect on regio- and stereoselectivities of the ene reactions. Thus, singlet oxygen attacks the double bond preferentially anti to the carbonyl group, affording only one regioisomeric hydroperoxide. If the reaction occurs from the opposite face, the other regioisomer is exclusively formed by severe electrostatic repulsion in a perepoxide intermediate. We explain this unusual behavior by the fixed geometry of spiro compounds and call it a "spiro effect" in singlet oxygen ene reactions. Y1 - 2021 U6 - https://doi.org/10.1111/php.13422 SN - 0031-8655 SN - 1751-1097 VL - 97 IS - 6 SP - 1289 EP - 1297 PB - Wiley CY - Malden, Mass. ER - TY - JOUR A1 - Schwarze, Thomas T1 - Determination of Pd2+ by fluorescence enhancement caused by an off-switching of an energy- and an electron transfer JF - ChemistrySelect N2 - In this paper, we introduce a fluorescent dye 1, which is able to detect selectively Pd2+ by a clear fluorescence enhancement (FE) in THF. In the presence of eight Pd2+ equivalents, we observed a fluorescence enhancement factor (FEF) of 28.3. The high Pd2+ induced FEF can be explained by an off switching of multiple quenching processes within 1 by Pd2+. In the free dye 1 a photoinduced electron transfer (PET) and energy transfer (ET) takes place and quenches the anthracenic fluorescence. The coordination of eight Pd2+ units by the alkylthio-substituted porphyrazine receptor suppresses the PET and ET quenching process and the anthracenic fluorescence is switched on. KW - Palladium ion KW - electron transfer KW - energy transfer KW - fluorescence KW - porphyrazine Y1 - 2021 U6 - https://doi.org/10.1002/slct.202003975 SN - 2365-6549 VL - 6 IS - 3 SP - 318 EP - 322 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sand, Patrick A1 - Schmidt, Bernd T1 - Pd-catalyzed oxidative sulfoalkenylation of acetanilides and traceless removal of the catalyst directing group JF - ChemistrySelect N2 - The palladium-catalyzed oxidative Heck-reaction, also referred to as Fujiwara-Moritani-reaction, has been investigated for the synthesis of styrenylsulfonyl compounds. Acetanilides and vinylsulfonyl compounds undergo dehydrogenative coupling reactions in moderate to quantitative yields, using benzoquinone as the oxidant of choice. Potassium peroxodisulfate, which had previously been identified as a superior oxidant for the coupling with acrylates, did not provide any coupling products with these olefins. Traceless removal of the catalyst directing group through a deacetylation-diazotation-coupling (DDC) sequence was demonstrated for 2-arylethene sulfones. KW - arenes KW - C− H activation KW - Heck reactions KW - Palladium KW - sulfones Y1 - 2021 U6 - https://doi.org/10.1002/slct.202101009 SN - 2365-6549 VL - 6 IS - 14 SP - 3563 EP - 3567 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Raju, Rajarshi Roy A1 - Koetz, Joachim T1 - Inner rotation of Pickering Janus emulsions JF - Nanomaterials : open access journal N2 - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles. KW - Janus droplets KW - Pickering emulsions KW - magnetic manipulation KW - gold nanoparticles KW - magnetite nanoparticles Y1 - 2021 U6 - https://doi.org/10.3390/nano11123312 SN - 2079-4991 VL - 11 IS - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Hermanns, Jolanda A1 - Keller, David T1 - School-related content knowledge in organic chemistry BT - How does the Bachelor and Master studies? JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society N2 - In this paper the development, use, and evaluation of tasks based on the construct of school-related content knowledge are described. The tasks were used in seminars on organic chemistry for bachelor and master preservice chemistry teachers at a German university. For the evaluation a questionnaire with open and closed items was used. The tasks were rated by the preservice chemistry teachers as relevant for their future profession as a chemistry teacher if the content of the tasks is part of the school curriculum. If the content does not belong to the school curriculum, they rated the nature of the tasks still as relevant; they seem to recognize the importance of conceptual knowledge for their future profession. However, the master's preservice teachers argued with this conceptual knowledge more often than the bachelor's preservice teachers. Although the study is cross-sectional, a certain shift from the focus on the content to conceptual knowledge from bachelor's to master's preservice teachers can be observed. KW - Organic Chemistry KW - Second-Year Undergraduate KW - Analogies/Transfer Y1 - 2021 U6 - https://doi.org/10.1021/acs.jchemed.0c01415 SN - 0021-9584 SN - 1938-1328 VL - 98 IS - 3 SP - 763 EP - 773 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Picconi, David T1 - Nonadiabatic quantum dynamics of the coherent excited state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline JF - Photochemical & photobiological sciences N2 - The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone.
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. KW - Excited state proton transfer KW - Quantum dynamics KW - Nonadiabatic effects KW - Spectroscopy KW - Coherences Y1 - 2021 U6 - https://doi.org/10.1007/s43630-021-00112-z SN - 1474-905X SN - 1474-9092 VL - 20 IS - 11 SP - 1455 EP - 1473 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Hermanns, Jolanda A1 - Keller, David T1 - How do preservice chemistry teachers rate tasks following the construct of school-related content knowledge in a concept-orientated course on organic chemistry? JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society N2 - In this paper, we describe a study on tasks following the construct of school-related content knowledge. We know from previous studies that such tasks were rated by the preservice chemistry teachers as important for their future profession. Those studies were conducted in a traditional course on organic chemistry which was organized around chemical families. Therefore, we used and evaluated the tasks again in a new course on organic chemistry which is organized around basic concepts in organic chemistry. The results of this evaluation show that the students rate the tasks equally well but use other arguments for their rating. They do not focus only on the content of the tasks and whether this content belongs to the school curriculum or not. The students of the conceptual course rated the content more often (95%) as important for their future profession compared with the students in the traditional course (57%). Both groups of students rated the importance of the nature of the task the same way. KW - Organic chemistry KW - Second-Year undergraduate KW - Alcohols KW - Curriculum KW - Molecular structure KW - Organic structure KW - Students Y1 - 2021 U6 - https://doi.org/10.1021/acs.jchemed.1c00593 SN - 0021-9584 SN - 1938-1328 VL - 98 IS - 11 SP - 3442 EP - 3449 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hermanns, Jolanda T1 - The task navigator following the STRAKNAP concept BT - Development, application, and evaluation of a new scaffold to support nonmajor chemistry students while solving tasks in organic chemistry JF - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society N2 - Educational Scaffolding was first mentioned in 1976 by Wood et al. Several examples for scaffolding in chemistry are also known from the literature. As written scaffolds, stepped supporting tools to support students while solving problems in organic chemistry were developed, applied, and evaluated. Although the students rated the tool as very helpful, a think-aloud study showed that the support given by this scaffold was not sufficient. As a further development of stepped supporting tools, task navigators were therefore developed, applied, and evaluated. This new scaffold gives tips on strategy, knowledge, and application of knowledge after the STRAKNAP concept. The evaluation of this tool shows that the students rated the tool as being very helpful. A think-aloud study showed that the scaffold supports the students while they solve a problem. Because of the stepwise construction of the task navigators and the providing of the knowledge needed for the application, the students can solve parts of the task successfully even if they do not solve all parts correctly; the students can always start from scratch. When students use the tool regularly, their knowledge of organic chemistry increases compared to students who did not use the tool at all. The task navigator is not only a scaffold for the content of the task but also for the development of methodological competences on the field of strategies and applying knowledge. KW - First-Year Undergraduate/General KW - Organic Chemistry KW - Distance KW - Learning/Chemistry Education Research Y1 - 2021 U6 - https://doi.org/10.1021/acs.jchemed.0c01162 SN - 0021-9584 SN - 1938-1328 VL - 98 IS - 4 SP - 1077 EP - 1087 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Krüger, Tobias A1 - Bramborg, Andrea A1 - Kelling, Alexandra A1 - Sperlich, Eric A1 - Linker, Torsten T1 - Birch Reduction of Arenes as an Easy Entry to γ-Spirolactones JF - European journal of organic chemistry N2 - A convenient method for the synthesis of γ-spirolactones in only 2–3 steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of ethylene oxide affords hydroxy acids, which undergo direct lactonization during work-up. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and dicarboxylic acids. Subsequent hydrogenation proceeds smoothly with Pd/C as catalyst and saturated γ-spirolactones are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation with Raney nickel or Wilkinson's catalyst to obtain products with 1 double bond. Overall, more than 30 new γ-spirolactones have been synthesized in analytically pure form. KW - Arenes KW - Birch reduction KW - Hydrogenation KW - Lactones KW - Synthetic methods Y1 - 2021 U6 - https://doi.org/10.1002/ejoc.202101018 SN - 1434-193X SN - 1099-0690 VL - 2021 IS - 46 SP - 6383 EP - 6391 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Neffe, Axel T. A1 - Zhang, Quanchao A1 - Hommes-Schattmann, Paul J. A1 - Lendlein, Andreas T1 - Ethylene oxide sterilization of electrospun poly(L-lactide)/poly(D-lactide) core/shell nanofibers JF - MRS advances N2 - The application of polymers in medicine requires sterilization while retaining material structure and properties. This demands detailed analysis, which we show exemplarily for the sterilization of PLLA/PDLA core-shell nanofibers with ethylene oxide (EtO). The electrospun patch was exposed to EtO gas (6 vol% in CO2, 1.7 bar) for 3 h at 45 degrees C and 75% rel. humidity, followed by degassing under pressure/vacuum cycles for 12 h. GC-MS analysis showed that no residual EtO was retained. Fiber diameters (similar to 520 +/- 130 nm) of the patches remained constant as observed by electron microscopy. Young's modulus slightly increased and the elongation at break slightly decreased, determined at 37 degrees C. No changes were detected in H-1-NMR spectra, in molar mass distribution (GPC) or in crystallinity measured for annealed samples with comparable thermal history (Wide Angle X-Ray Scattering). Altogether, EtO emerged as suitable sterilization method for polylactide nanofibers with core-shell morphology. Y1 - 2021 U6 - https://doi.org/10.1557/s43580-021-00058-5 SN - 2059-8521 VL - 6 IS - 33 SP - 786 EP - 789 PB - Springer CY - Cham ER - TY - JOUR A1 - Rethfeldt, Nina A1 - Brinkmann, Pia A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Köllner, Nicole A1 - Altenberger, Uwe A1 - Löhmannsröben, Hans-Gerd T1 - Detection of Rare Earth Elements in Minerals and Soils by Laser-Induced Breakdown Spectroscopy (LIBS) Using Interval PLS JF - Minerals N2 - The numerous applications of rare earth elements (REE) has lead to a growing global demand and to the search for new REE deposits. One promising technique for exploration of these deposits is laser-induced breakdown spectroscopy (LIBS). Among a number of advantages of the technique is the possibility to perform on-site measurements without sample preparation. Since the exploration of a deposit is based on the analysis of various geological compartments of the surrounding area, REE-bearing rock and soil samples were analyzed in this work. The field samples are from three European REE deposits in Sweden and Norway. The focus is on the REE cerium, lanthanum, neodymium and yttrium. Two different approaches of data analysis were used for the evaluation. The first approach is univariate regression (UVR). While this approach was successful for the analysis of synthetic REE samples, the quantitative analysis of field samples from different sites was influenced by matrix effects. Principal component analysis (PCA) can be used to determine the origin of the samples from the three deposits. The second approach is based on multivariate regression methods, in particular interval PLS (iPLS) regression. In comparison to UVR, this method is better suited for the determination of REE contents in heterogeneous field samples. View Full-Text KW - LIBS KW - rare earth elements KW - minerals KW - PCA KW - iPLS regression Y1 - 2021 U6 - https://doi.org/10.3390/min11121379 SN - 2075-163X VL - 11 SP - 1 EP - 17 PB - MDPI CY - Basel, Schweiz ER - TY - JOUR A1 - Balderas-Valadez, Ruth Fabiola A1 - Pacholski, Claudia T1 - Plasmonic Nanohole Arrays on Top of Porous Silicon Sensors BT - A Win-Win Situation JF - ACS applied materials & interfaces N2 - Label-free optical sensors are attractive candidates, for example, for detecting toxic substances and monitoring biomolecular interactions. Their performance can be pushed by the design of the sensor through clever material choices and integration of components. In this work, two porous materials, namely, porous silicon and plasmonic nanohole arrays, are combined in order to obtain increased sensitivity and dual-mode sensing capabilities. For this purpose, porous silicon monolayers are prepared by electrochemical etching and plasmonic nanohole arrays are obtained using a bottom-up strategy. Hybrid sensors of these two materials are realized by transferring the plasmonic nanohole array on top of the porous silicon. Reflectance spectra of the hybrid sensors are characterized by a fringe pattern resulting from the Fabry–Pérot interference at the porous silicon borders, which is overlaid with a broad dip based on surface plasmon resonance in the plasmonic nanohole array. In addition, the hybrid sensor shows a significant higher reflectance in comparison to the porous silicon monolayer. The sensitivities of the hybrid sensor to refractive index changes are separately determined for both components. A significant increase in sensitivity from 213 ± 12 to 386 ± 5 nm/RIU is determined for the transfer of the plasmonic nanohole array sensors from solid glass substrates to porous silicon monolayers. In contrast, the spectral position of the interference pattern of porous silicon monolayers in different media is not affected by the presence of the plasmonic nanohole array. However, the changes in fringe pattern reflectance of the hybrid sensor are increased 3.7-fold after being covered with plasmonic nanohole arrays and could be used for high-sensitivity sensing. Finally, the capability of the hybrid sensor for simultaneous and independent dual-mode sensing is demonstrated. KW - optical sensors KW - porous silicon KW - surface plasmon resonance KW - plasmonic KW - nanohole arrays KW - bottom-up fabrication Y1 - 2021 U6 - https://doi.org/10.1021/acsami.1c07034 SN - 1944-8244 SN - 1944-8252 VL - 13 IS - 30 SP - 36436 EP - 36444 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hermanns, Jolanda T1 - Training OC BT - A new course concept for training the application of basic concepts in organic chemistry JF - Journal of chemical education N2 - The course design "Training OC" for training the application of basic concepts consists of four topics: formula language, structure-property relations, reaction mechanisms, and complex tasks that the students should solve with the conceptual knowledge they acquired in the first three topics. A main goal of the course was to enable the students to solve reaction mechanisms. To achieve the goals of the course, several games were specially designed and used. The course was conducted at a German university with ca. 30 students who participated voluntarily. The course was evaluated by several tools: students' products were collected in the course, there were two pre/post-tests, and additionally, interviews on the strategy of designing reaction mechanisms were conducted. The performance of the teacher and the self-assessment of the students were also part of the evaluation. The results of the written exam were compared with the results of the bachelor chemistry major students. The course "Training OC" was rated very well by the students. They were of the opinion that they learned the application of basic concepts taught in this course. This is supported by the results of the evaluation and the written exams. The course concept of Training OC will therefore become a permanent part of the course "Organic Chemistry I" which will be redesigned for the next round in 2020-21. KW - Second-Year Undergraduate KW - Organic Chemistry KW - Humor/Puzzles/Games KW - Collaborative/Cooperative Learning Y1 - 2020 U6 - https://doi.org/10.1021/acs.jchemed.0c00567 SN - 0021-9584 SN - 1938-1328 VL - 98 IS - 2 SP - 374 EP - 384 PB - American Chemical Society. Division of Chemical Education CY - Washington ER - TY - JOUR A1 - Kwesiga, George A1 - Sperlich, Eric A1 - Schmidt, Bernd T1 - Scope and applications of 2,3-oxidative aryl rearrangements for the synthesis of isoflavone natural products JF - The journal of organic chemistry N2 - The reaction of flavanones with hypervalent iodine reagents was investigated with a view to the synthesis of naturally occurring isoflavones. In contrast to several previous reports in the literature, we did not observe the formation of any benzofurans via a ring contraction pathway, but could isolate only isoflavones, resulting from an oxidative 2,3-aryl rearrangement, and flavones, resulting from an oxidation of the flavanones. Although the 2,3-oxidative rearrangement allows a synthetically useful approach toward some isoflavone natural products due to the convenient accessibility of the required starting materials, the overall synthetic utility and generality of the reaction appear to be more limited than previous literature reports suggest. Y1 - 2021 U6 - https://doi.org/10.1021/acs.joc.1c01375 SN - 0022-3263 SN - 1520-6904 VL - 86 IS - 15 SP - 10699 EP - 10712 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Photooxygenation of naphthalene JF - ChemPhotoChem N2 - The photooxygenation of naphthalene to the corresponding endoperoxide (EPO) under various conditions is described. Substantial conversion is only observed at -10 degrees C and after more than two days, indicating that the [4+2] cycloaddition of singlet oxygen to this acene proceeds much more slowly than corresponding reactions of substituted naphthalenes, a rate constant of k = 5.4 +/- 0.3 M(-1)s(-1) was determined by competition kinetics. Another problem is the thermal lability and photochemical cleavage of the naphthalene EPO. We investigated the mechanism of this radical process depending on the light source and sensitizer in comparison to known cyclohexadiene EPO. Thus, bisepoxides and keto epoxides are formed after homolysis of the O-O bond by irradiation with sodium lamps or blue LEDs and subsequent cyclization. This process is accelerated by the sensitizers methylene blue and 9,10-dicyanoanthracene, indicating an electron transfer mechanism. Finally, the cleavage of the peroxidic bond is inhibited with red LEDs, and photooxygenation under such conditions affords 20 % EPO. Thus, we could demonstrate that contrary to literature statements singlet oxygen does indeed react with naphthalene. KW - naphthalene KW - photooxygenation KW - reaction mechanisms KW - reactive KW - intermediates KW - singlet oxygen Y1 - 2021 U6 - https://doi.org/10.1002/cptc.202100097 VL - 5 IS - 11 SP - 1004 EP - 1008 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Bauch, Marcel A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Stereoselective [4+2] Cycloaddition of Singlet Oxygen to Naphthalenes Controlled by Carbohydrates JF - Molecules : a journal of synthetic chemistry and natural product chemistry N2 - Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form. KW - singlet oxygen KW - photooxygenation KW - naphthalenes KW - carbohydrates KW - stereoselectivity KW - auxiliary control KW - [4+2] cycloaddition Y1 - 2021 U6 - https://doi.org/10.3390/molecules26040804 SN - 1420-3049 VL - 16 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bäckemo, Johan Dag Valentin A1 - Liu, Yue A1 - Lendlein, Andreas T1 - Bio-inspired and computer-supported design of modulated shape changes in polymer materials JF - MRS communications / a publication of the Materials Research Society N2 - The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap. KW - Additive manufacturing KW - Biomimetic KW - Shape memory KW - Modelling KW - Polymer Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00056-6 SN - 2159-6867 VL - 11 IS - 4 SP - 462 EP - 469 PB - Springer CY - Berlin ER - TY - JOUR A1 - López-Salas, Nieves A1 - Albero, Josep T1 - CxNy BT - new carbon nitride organic photocatalysts JF - Frontiers in Materials N2 - The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials. KW - CXNY KW - carbon nitrides KW - C2N KW - C3N KW - C1N1 KW - C3N5 KW - photocatalysis Y1 - 2021 U6 - https://doi.org/10.3389/fmats.2021.772200 SN - 2296-8016 VL - 8 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Lendlein, Andreas A1 - Heuchel, Matthias T1 - Shape-memory polymers designed in view of thermomechanical energy storage and conversion systems BT - Effective temporary shape fixation by strain-induced formation of supramolecular nanostructures enables high energy density one-way shape-memory polymers JF - ACS central science KW - Actuators KW - Deformation KW - Energy KW - Energy storage KW - Polymers Y1 - 2021 U6 - https://doi.org/10.1021/acscentsci.1c01032 SN - 2374-7951 VL - 7 IS - 10 SP - 1599 EP - 1601 PB - American Chemical Society CY - Washington ER -