Ene reductases from the Old Yellow Enzyme (OYE) family reduce the C=C double bond in α,β‐unsaturated compounds bearing an electron‐withdrawing group, for example, a carbonyl group. This asymmetric reduction has been exploited for biocatalysis. Going beyond its canonical function, we show that members of this enzyme family can also catalyze the formation of C−C bonds. α,β‐Unsaturated aldehydes and ketones containing an additional electrophilic group undergo reductive cyclization. Mechanistically, the two‐electron‐reduced enzyme cofactor FMN delivers a hydride to generate an enolate intermediate, which reacts with the internal electrophile. Single‐site replacement of a crucial Tyr residue with a non‐protic Phe or Trp favored the cyclization over the natural reduction reaction. The new transformation enabled the enantioselective synthesis of chiral cyclopropanes in up to >99 % ee.

Processing oriented metal–organic frameworks (MOFs) as thin films is a key challenge for their application to device fabrication. However, typical fabrication methods cannot generate precisely oriented crystals on commercially relevant scales (i.e., cm2). This limits access to applications that require anisotropic functional properties (e.g., separation, optics, and electronics). Currently, highly oriented copper‐based MOFs are synthesized via the addition of the organic MOF component to an ethanolic solution of manually aligned Cu(OH)2 nanobelt films. In this work, the optimization of a semi‐automatic method for the fabrication of precisely oriented MOF films that affords a 100% yield of high quality ceramic films at the centimeter scale is reported. This improved fabrication protocol will facilitate the progress of heteroepitaxially grown MOFs for molecular separators and micro‐opto‐electronic devices.

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, a patternable oriented MOF film is designed: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH) 2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylate ligand (Br 2 BDC) into a copper-based MOF Cu 2 L 2 DABCO (DABCO = 1,4-diazabicyclo[2.2.2]octane; L = BDC/Br 2 BDC). The lithographed samples act as diffraction gratings upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, the alignment of the dye in the MOF is demonstrated. By controlling the functional response to light, this MOF patterning protocol can be used for the microfabrication of optical components for photonic devices.

No abstract

En-Reduktasen der "Old YellowE nzyme"(OYE)-Familie reduzieren die C = C-Doppelbindung in a,b-ungesät-tigten Verbindungen, die eine elektronenziehende Gruppe (z. B. eine Carbonyl-Gruppe) Diels-Alder-Reaktionen [5] und andere.[6] Wirb erichten nun über einen neuen Ty pe iner enzymatischen C-C-Bindungsknüpfung,b ei dem durch eine Kombination aus SubstratDesign und Protein-Engineering die asymmetrische reduktive Cyclisierung durch En-Reduktasen ermçglicht wird. EnReduktasen der "Old Yellow Enzyme"(OYE)-Familie sind Enzyme,d ie elektronenarme Olefine reduzieren, wie sie in a,b-ungesättigten Carbonylverbindungen vorliegen. In den letzten Jahren wurde das Synthesepotenzial dieser Enzymfamilie fürb iokatalytische Anwendungen erschlossen. [7,8] Gemäßd em allgemein anerkannten Mechanismus wird vom reduzierten Flavinmononukleotid(FMN)-Cofaktor ein Hydrid auf das b-Kohlenstoffatom übertragen, wobei sich ein Enolat bildet, das danach mithilfe von Ty r-OH, das als Protonquelle fungiert, protoniert wird.[9] Wirv ermuteten, dass wir diese Enzyme füre ine reduktive Carbocyclisierung nutzen (oder modifizieren) kçnnten, wenn wir ihnen Substrate anbieten würden, die ein internes Elektrophil aufweisen, das mit dem entstehenden Enolat unter Ringbildung reagieren kçnnte. [10,11] Fürd ieses Ziel wären Carbonylgruppen, Alkylhalogenide oder Epoxide als Elektrophile denkbar (Schema 1).Da sich die Wildtyp(WT)-Enzyme OPR3 (12-Oxophytodiensäure-Reduktase 3) aus der Tomate (Solanum lycopersicum)und YqjM aus Bacillus subtilis schon in der Biokatalyse fürd ie Reduktion von Alkenen bewährt haben, [12] untersuchten wir, ob diese Enzyme eine reduktive Carbocyclisierung mit Substraten eingehen würden, die verschiedene elektronenziehende Substituenten und w-Halogenalkylgruppen unterschiedlicher Kettenlänge,die zu verschieden großen Ringen führen würden, tragen (Schema 2; Tabellen 1u nd S1 (Hintergrundinformationen)). Schon diese WT-Enzyme

Luminescent Metal-organic Frameworks (MOFs) are known to spontaneously self-assemble on human fingerprints. Here, we investigate the different chemical components of fingerprints and determine that MOF growth is predominantly induced by...

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, we design a patternable oriented MOF film: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylic ligand (Br2BDC) into a copper-based MOF Cu2L2DABCO (L=BDC/Br2BDC). The lithographed samples act as a diffraction grating upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, we demonstrate the alignment of the dye in the MOF. By controlling the functional response to light, this MOF patterning protocol could be used for the microfabrication of optical components for photonic devices.

3D-oriented metal-organic framework (MOF) films and patterns have recently emerged as promising platforms for sensing and photonic applications. These oriented polycrystalline materials are typically prepared by heteroepitaxial growth from aligned inorganic nanostructures and display anisotropic functional properties, such as guest molecule alignment and polarized fluorescence. However, to identify suitable conditions for the integration of these 3D-oriented MOF superstructures into functional devices, the effect of water (gaseous and liquid) on different frameworks should be determined. We note that the hydrolytic stability of these heteroepitaxially grown MOF films is currently unexplored. In this work, we present an in-depth analysis of the structural evolution of aligned 2D and 3D Cu-based MOFs grown from Cu(OH)2 coatings. Specifically, 3D-oriented Cu2L2 and Cu2L2DABCO films (L = 1,4-Benzenedicarboxylic acid, BDC; Biphenyl-4,4-dicarboxylic acid, BPDC, DABCO = 1,4-Diazabicyclo[2.2.2]octane) were exposed to 50% relative humidity (RH), 80% RH and liquid water. The combined use of X-ray diffraction, infrared spectroscopy, and scanning electron microscopy shows that the sensitivity towards humid environments critically depends on the presence of the DABCO pillar ligand. While oriented films of 2D MOF layers stay intact upon exposure to all levels of humidity, hydrolysis of Cu2L2DABCO is observed. In addition, we report that in environments with high water content, 3D-oriented Cu2(BDC)2DABCO recrystallizes as 3D-oriented Cu2(BDC)2. The heteroepitaxial MOF-to-MOF transformation mechanism was studied with in situ synchrotron experiments and time-resolved AFM measurements. These findings provide valuable information on the stability of oriented MOF films for their application in functional devices and highlight the potential for the fabrication of 3D-oriented superstructures via MOF-to-MOF transformations.