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A Visible-Light-Driven Molecular Motor Based on Pyrene
摘要： The aromatic core of an overcrowded alkene-based molecular motor is extended with the goal of inducing isomerization with visible light instead of harmful UV light. In our design, the common naphthalene moiety in the upper half of the motor is changed to pyrene. The photochemical and thermal isomerization processes are studied in detail using DFT calculations as well as NMR and UV/vis spectroscopy. Our studies confirm that extension of the π-system of the upper half successfully leads to a shift of the excitation wavelength into the visible region, while retaining proper rotary function.
关键词： Molecular Switches,Photochromism,Overcrowded Alkenes,Molecular Motors,Pyrene
更新于2025-09-23 15:23:52
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Oxidative and reductive cyclization in stiff dithienylethenes
摘要： The electrochemical behavior of stiff dithienylethenes, undergoing double bond isomerization in addition to ring-closure, has been investigated. Electrochromism was observed in almost all cases, with the major pathway being the oxidatively induced cyclization of the open isomers. The influence of the ring size (to lock the reactive antiparallel conformation) as well as substituents (to modulate the redox potential) on the electrocyclization was examined. In the series of derivatives with 6-membered rings, both the E- and the Z-isomer convert to the closed isomer, whereas for the 7-membered rings no cyclization from the E-isomer was observed. For both stiff and normal dithienylethenes bearing benzonitrile substituents an additional and rare reductive electrocyclization was observed. The mechanism underlying both observed electrocyclization pathways has been elucidated.
关键词： (spectro)electrochemistry,electrochromism,molecular switches,diarylethenes
更新于2025-09-23 15:22:29
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Central-to-Helical-to-Axial-to-Central Transfer of Chirality with a Photoresponsive Catalyst
摘要： Recent advances in molecular design have displayed striking examples of dynamic chirality transfer between various elements of chirality, e.g. from central to either helical or axial chirality and vice versa. While considerable progress in atroposelective synthesis has been made, it is intriguing to design chiral molecular switches able to provide selective and dynamic control of axial chirality with an external stimulus to modulate stereochemical functions. Here, we report the synthesis and characterization of a photoresponsive bis(2-phenol)-substituted molecular switch 1. The unique design exhibits a dynamic hybrid central-helical-axial transfer of chirality. The change of preferential axial chirality in the biaryl motif is coupled to the reversible switching of helicity of the overcrowded alkene core, dictated by the fixed stereogenic center. The potential for dynamic control of axial chirality was demonstrated by using (R)-1 as switchable catalyst to direct the stereochemical outcome of the catalytic enantioselective addition of diethylzinc to aromatic aldehydes, with successful reversal of enantioselectivity for several substrates.
关键词： atropisomers,photoresponsive catalyst,chirality transfer,photoisomerization,dynamic selectivity control,molecular switches
更新于2025-09-23 15:21:01
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New photochromic indoline spiropyrans containing cationic substituent in the 2H-chromene moiety
摘要： New indoline spiropyrans containing conjugated cationic fragments and bulky substituents in the 2H-chromene moiety were synthesized by a simple one-pot method. The structures of the obtained compounds were confirmed by 1H and 13C NMR (including 2D methods) and IR spectroscopy, as well as by element analysis and HRMS. Molecular structure of 1,3,3-trimethyl-60-formyl-80-benzyl-spiro[indoline-2,20-2H-chromene] was refined by single crystal X-ray. A comparative analysis of the spectral and photochromic properties of salt spiropyrans and similar structures without a cationic fragment was carried out. It was found that the introduction of the cationic substituent at the 60-position of the 2H-chromene moiety leads to a significant increase in the photoinduced isomer's lifetime.
关键词： Indolines,Molecular switches,2H-chromenes,Photochromism,Single crystal X-ray analysis,Spiropyrans
更新于2025-09-09 09:28:46