Institut de Science et d'Ingénierie Supramoléculaires , Université de Strasbourg , 8 allée Gaspard Monge , 67000 Strasbourg , France.
J Am Chem Soc. 2018 Jun 20;140(24):7647-7657. doi: 10.1021/jacs.8b03633. Epub 2018 Jun 12.
We implement sensitized alkoxyamines as "photodynamic covalent bonds"-bonds that, while being stable in the dark at ambient temperatures, upon photoexcitation efficiently dissociate and recombine to the bound state in a fast thermal reaction. This type of bond allows for the photochemically induced exchange of molecular building blocks and resulting constitutional variation within dynamic reaction networks. To this end, alkoxyamines are coupled to a xanthone unit as triplet sensitizer enabling their reversible photodissociation into two radical species. By studying the photochemical properties of three generations of sensitized alkoxyamines it became clear that the nature and efficiency of triplet energy transfer from the sensitizer to the alkoxyamine bond as well as the reversibility of photodissociation crucially depends on the structure of the nitroxide terminus. By employing the thus designed photodynamic covalent bonding motif, we demonstrate how to use light energy to shift a dynamic covalent reaction network away from its thermodynamic minimum into a photostationary state. The network could be repeatedly switched between its minimum and kinetically trapped out-of-equilibrium state by thermal scrambling and selective photoactivation of sensitized alkoxyamines, respectively.
我们将敏化烷氧基胺作为“光动力共价键”-在室温黑暗条件下稳定的键，在光激发下，能够有效地解离，并在快速热反应中重新结合到束缚态。这种键允许光化学诱导的分子构建块的交换和动态反应网络中的结构变化。为此，烷氧基胺与作为三重态敏化剂的呫吨单元偶联，从而能够将其可逆光解为两种自由基物种。通过研究三代敏化烷氧基胺的光化学性质，我们清楚地表明，三重态能量从敏化剂向烷氧基胺键的转移的性质和效率以及光解的可逆性，关键取决于氮氧自由基末端的结构。通过采用这种设计的光动力共价键模体，我们展示了如何利用光能将动态共价反应网络从其热力学最小状态转移到光稳定状态。通过热重排和选择性敏化烷氧基胺的光激活，分别可以将网络在其最小和动力学捕获的非平衡状态之间反复切换。
