The change of light regulated configuration of [organic] aromatic oligomeric fold

Some of our common biological macromolecules, such as DNA, protein microtubules, the shell protein of tobacco mosaic virus and so on, contain high-level spiral structure This complex multi-level structure not only endows these macromolecules with specific functions, but also can store specific "information" in them In the past two decades, chemists have become more and more interested in this folding phenomenon, and attempt to synthesize unnatural oligomers with specific structures to explore the life process in organisms Therefore, a new research field, foldaber chemistry, is born, which exists in the intersection of physical chemistry, organic chemistry, chemical biology and supramolecular chemistry In the past two decades, folding bodies based on various driving forces such as hydrogen bond, hydrophobic interaction, donor receptor interaction, ligand interaction and free radical interaction have been developed Not only that, scientists also regulate the folding process of folding bodies through various external stimuli, and apply them to nanotechnology, molecular machines, memory storage materials, transmembrane transport and other fields What's more, foldables have shown good application prospects in reaction catalysis, antibacterial and antiviral research and functional regulation of biomacromolecules Figure 1 The composition, structure and different configuration of oligomeric fold (picture source: angel Chem Int ed.) recently, Dr Yann Ferrand, the first university of Bordeaux, France, and Professor Ivan HUC, University of Munich, Germany, jointly reported an aromatic oligomer fold (Figure 1c) They found that when 1,8-azaanthracene was incorporated into the aromatic oligomer to form a folding body, they would tend to form a parallel stacking structure due to π - π stacking (Fig 1b) Anthracene will undergo [4 + 4] cycloaddition reaction under light, so the author infers that the folding body can also undergo conformational transformation by light, and the existence of this transformation is confirmed by means of NMR, single crystal diffraction, molecular simulation, etc This achievement was published in German Applied Chemistry (DOI: 10.1002 / anie 201902378) under the title of "light controlled conformal switch of an organic oligoamidefoldamer" The composition of aromatic oligofoldable 3 is relatively simple, which is mainly divided into central link part, photoresponse structure part and polymer part Among them, the central link part is composed of derivatives of 1,3-diamino-4,6-dinitrobenzene (Fig 1D, t), the light response part is composed of derivatives of 1,8-diazoanthene (Fig 1D, a h), and the polymer part is composed of three aromatic compounds (Fig 1D, QPN), and the aromatic oligomeric foldable 3 with photoresponsiveness was obtained by amido condensation Due to the complex structure of 3, the author first used 1 (Fig 1E) with similar structure but no oligomer for preliminary test The NMR results show that under the light of 320-390 nm, compound 1 can basically completely transform into cycloaddition product 2 within 20 minutes (Fig 2, left) Similar to the reaction of anthracene monomer, cycloaddition reaction product 2 can also be reversed into 1 under the condition of heating (right of Fig 2), but different from anthracene, the same effect can not be obtained by light After confirming that the foldable precursor can carry out photoreaction, the author plans to carry out similar research on the photoresponsiveness of 3, but before that, the author found that there are many conformations of 3 in the solution, and confirmed the existence of these conformations by single crystal diffraction (Fig 3a) Through the analysis of single crystal structure and molecular simulation results, it is found that no matter which configuration, the two anthracene structures are in parallel state, but there is a certain deviation, so they are not the ideal spatial configuration for cycloaddition reaction In spite of this, 3 will undergo cycloaddition reaction after being illuminated, and the product is 4 (Fig 3C), but the reaction will take 4 hours to complete Fig 3 A) the conversion between different configurations of foldable 3; b) the NMR spectra of foldable 3 under different illumination time; c) the crystal structure of photoaddition product 4 (picture source: angel Chem Int ed.) Full text author: bappaditya gole, Brice Kauffmann, Victor maurizot, Ivan Hu C, and Yann Ferrand.