Adijiang Adila, Ge Yunlong, Feng Hefa, Yan Yan, Zuo Xin, Wang Haoyu, Zhao Xueyan, Tan Min, Zhang Surong, Xu Xiaona, Chen Lichuan, Wang Chuankui, Li Zongliang, Xiang Dong
Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Institute of Modern Optics and Centre of Single-Molecule Science, Nankai University Tianjin 300350 China
Key Laboratory of Medical Physics and Image Processing of Shandong Province, School of Physics and Electronics, Shandong Normal University Jinan 250358 China
Chem Sci. 2025 Sep 5. doi: 10.1039/d5sc06085k.
The keto-enol tautomerism, involving a reversible isomerization of the molecule, plays a critical role in organic synthesis, biological activity, and molecular-scale charge transport. It is therefore essential to manipulate the process of keto-enol tautomerism. Unlike typical ketones, β-diketones exist dominantly in the enol form and it is a great challenge to realize enol-keto tautomerism due to the formation of intramolecular hydrogen bonds in the enol form. Here, monitoring of the conductance evolution of thousands of single-molecule junctions, we demonstrated that the enol → keto transformation can be significantly promoted by confined ultraviolet (UV) irradiation at an extremely low intensity (1‰ of sunshine) employing antenna electrodes. Our study reveals that the conductance of the enol form is an order of magnitude larger than that of the keto form although both have similar molecular lengths and identical anchoring groups, and the enol form shows a current rectification behaviour which is completely absent in the keto form. Supported by UV-vis measurements, wavelength-dependent conductance measurements, and theoretical calculations, the mechanism for the enol → keto transformation promoted by the gap-electrode-confined optical field was elucidated, offering a new strategy to regulate the tautomerism processes at the single molecule level, and implying a potential multi-functional application of β-diketones in the fabrication of rectifiers and synchronous switches.
酮-烯醇互变异构涉及分子的可逆异构化，在有机合成、生物活性和分子尺度电荷传输中起着关键作用。因此，控制酮-烯醇互变异构过程至关重要。与典型酮不同，β-二酮主要以烯醇形式存在，由于烯醇形式中分子内氢键的形成，实现烯醇-酮互变异构极具挑战性。在此，通过监测数千个单分子结的电导演变，我们证明了采用天线电极在极低强度（阳光强度的1‰）的受限紫外（UV）照射下，烯醇→酮的转变可得到显著促进。我们的研究表明，尽管烯醇形式和酮形式具有相似的分子长度和相同的锚定基团，但烯醇形式的电导比酮形式大一个数量级，并且烯醇形式表现出酮形式完全不存在的电流整流行为。在紫外-可见光谱测量、波长依赖电导测量和理论计算的支持下，阐明了间隙电极受限光场促进烯醇→酮转变的机制，为在单分子水平调控互变异构过程提供了一种新策略，并暗示了β-二酮在整流器和同步开关制造中的潜在多功能应用。
