In 2009, when Tian Yaming, a 19-year-old from Hengshui, Hebei, left his hometown to report to the Chemistry Department of Shanxi University, he might not have expected that he would spend 15 years studying in chemistry classes.

After completing his undergraduate degree, he successively obtained a master's degree and a doctorate at Shanghai University and the University of Würzburg in Germany, respectively. Currently, Tian Yaming is engaged in postdoctoral research at the University of Regensburg in Germany.

Before his 34th birthday, he received an excellent birthday gift - a first-authored paper published in Science.

Now, he is preparing to contact domestic work units. Despite having published a top journal paper, he appears somewhat modest: "If I can meet the requirements of relevant scientific research institutions in my country, I would be very happy to return to work."

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So, what is the achievement introduced in Tian Yaming's Science paper? It is reported that in this study, he and his current team proposed a new method for synthesizing complex molecules.The working principle of this method lies in: when molecules waiting for a reaction are applied to the surface of water, a thin film is formed on the water surface, thereby creating an "oil-water" interface.

Under the irradiation of light, it will trigger the reactants to react at the interface. For this reaction mode, it utilizes the phenomenon that water-insoluble solid organic molecules can form a thin film on the water surface by lowering the melting point (just like an oil film on the water surface), thereby creating an ideal reaction platform for efficient photochemical conversion.

For the active hydrogen in the reactants, it can form hydrogen bonds with water at the oil-water phase interface, thereby further accelerating the progress of the photochemical reaction.

Research shows that this technology has good applicability and has been demonstrated in more than 160 examples, one of which is the modification of drug molecules. Moreover, this reaction system can achieve a large amount of synthesis under flow phase conditions.

Nowadays, photochemical reactions on the water interface can be carried out without the need for organic solvents or other reaction additives, making the production of chemical products more efficient and environmentally friendly.This strategy provides a new approach for the organic synthesis of water-insoluble organic molecules at the water interface, expanding the application of water in organic synthesis and having a significant impact on photochemistry and organic synthesis in aqueous media.

It is expected that the results of this study will achieve the following applications:

Firstly, for large-scale flow synthesis, using the method of reducing melting point to form an oil phase can accelerate the reaction of organic synthesis, especially the photochemical reactions carried out in aqueous media.

Secondly, for green synthesis and industrial production, to reduce the environmental impact during the preparation of chemicals.

Thirdly, for the design of synthetic routes in drug development and drug production, that is, by accelerating photochemical reactions at the water-oil interface, to improve the efficiency and selectivity of drug modification.In detail, this method can be utilized to improve the solubility and efficacy of drugs, thereby enhancing the therapeutic effects and the efficiency of drug delivery.

Fourthly, it is used in the design and synthesis of functional materials. By controlling the rate and selectivity of photochemical reactions at the water-oil interface, materials with specific structures and properties can be prepared, such as photosensitive materials, catalysts, nanoparticles, etc.

These materials have potential application value in the fields of energy, environment, and electronic devices.

The Road Less Traveled: Using Pure Water as a Photochemical Reaction SolventIt is reported that organic chemists have always avoided using water as a reaction medium. The main reasons are twofold: first, the limited solubility of reactants, and second, the susceptibility of reactants to hydrolysis in water.

However, since 1980, when American chemist Ronald Breslow and his team revealed that water can significantly accelerate the Diels-Alder reaction involving nonpolar compounds, the assumption that "organic reactions require organic solvents to dissolve reactants" has been challenged.

Subsequent studies have shown that for some organic transformations, an aqueous environment can provide faster reaction rates and better selectivity than organic solvents.

In 2005, the team of American chemist and Nobel laureate Karl Barry Sharpless reported a series of organic transformation achievements.

They found that when pure water is used as the sole reaction medium, the reaction rate begins to increase, even surpassing the performance of nonpolar and polar organic solvents.Subsequently, experimental and theoretical research by the Sharpless group confirmed that water has unique properties in accelerating organic reactions. These properties include hydrophobic effects, traditional hydrogen bonding, and anti-hydrogen bonding effects, among others.

At the same time, these properties can have differential impacts on the reaction process under different conditions of "in water" and "on water."

However, despite the widely recognized accelerating properties of water for organic transformations, the use of pure water as a solvent for photochemical reactions is a research area that is rarely explored.

Additionally, by forming chemical bonds between atoms, complex molecules required for the preparation of drugs, pesticides, and high-performance materials can be synthesized using synthetic chemistry methods.

These synthetic reactions typically require organic solvents, metal catalysts, and reagents such as acids or bases. However, not all auxiliary materials and solvents can be recycled, which can lead to the generation of a large amount of waste.Based on the aforementioned challenges, Tian Yaming and his team proposed this method for synthesizing complex molecules.

Inspired by the unique phase transition phenomena of surfaces and interfaces

Tian Yaming said: "Our inspiration comes from the unique phase transition phenomena of surfaces and interfaces, which do not occur within the interior of the material. One of the most famous examples is the phenomenon first predicted by British scientist Michael Faraday in 1842, that is, a thin layer of liquid water formed on the surface of ice."

This liquid water is produced due to the reduction of the melting point at the interface, which makes the ice slippery. After investigating and analyzing the current organic photochemical transformation in aqueous solutions, he and his colleagues began to think: Can this phenomenon of phase transition (melting) behavior at the interface be applied to organic synthetic chemistry?It is important to understand that when two different solid compounds form a mixture, the melting point of the mixture is lower, which allows for the formation of a eutectic system, and this process is significantly influenced by the interactions between the compounds (such as hydrogen bonding).

Based on this, they immediately thought of electron donor-acceptor (EDA, Electron Donor-Acceptor Interaction) complexes.

When two compounds form an EDA complex, the interaction between them may lead to the formation of new molecular structures, which could potentially alter the physical properties of the mixture, such as its melting point.

This is because the formation of an EDA complex typically involves charge transfer or intermolecular interactions, which can affect the cohesive properties of the mixture, leading to the disruption of the compound's lattice structure, causing the molecules in the mixture to be more disordered and loosely arranged, thereby promoting the transition of the substance from solid to liquid.

After determining the direction of research, the research group chose substrates with different electron affinities to design the experiment. To their delight, they found that solid organic molecules, when mixed in certain proportions, could indeed form a eutectic system, and in the presence of water, would form an "oil-water" two-phase system.Due to the presence of hydrophobic interactions, the oil phase further spreads on the water surface, thereby forming a larger oil-water interface, which in turn increases the absorption cross-section of the reactants.

Through a series of experimental optimizations, they successfully carried out photochemical coupling reactions at the oil-water interface without the need for any additives.

Subsequently, they verified the application capability of this reaction system among more than 160 types of reaction substrates. To enhance the application value of this reaction mode, the team built a flow photochemical synthesis apparatus, achieving the synthesis of a larger-scale reaction system.

Next, the research group focused on determining the mechanism of the reaction at the oil-water interface. By using a variety of experimental methods, especially with the help of nuclear magnetic resonance, they obtained key evidence of the reaction occurring at the interface, and thus the research finally came to an end.

Finally, the related paper was published in Science[1] with the title "Accelerated photochemical reactions at oil-water interface exploiting melting point depression."Yaming Tian is the first author, and Burkhard König from the University of Regensburg in Germany serves as the corresponding author.

Next, they will continue to delve deeper into the mechanisms of photochemical reactions at the oil-water interface, exploring more details about the interactions at the interface and the reaction kinetics. Additionally, they will explore the applicability of more types of organic reactions at the oil-water interface.

They will also improve these reactions, such as developing new photocatalytic reaction systems, for use in fields such as synthetic chemistry and medicinal chemistry.