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After submitting the last step of ICIN-2F/Cl, Xu Qiu began to deal with the reaction product of the first step of IDTT, which is the TT-B-TT structure with two ester groups connected to the central benzene ring (B).

The dot-plate developing agent used dichloromethane and petroleum ether at a volume ratio of 1:1. The results showed that the main product dots were relatively deep, and the yield should not be low. After all, it was synthesized for more than 24 hours.

Xu Qiu judged that this kind of reaction that requires a long reaction time may be more suitable for microwave reactors, and it is estimated that the reaction time can be shortened a lot, so you can try it later.

Wu Shengnan also had experience with columns before, but he had never used this kind of advanced high-pressure liquid chromatography machine. He used to pass columns by hand. It might take a day to pass a column. Now that she sees this kind of machine, it is natural His eyes were shining, and he exclaimed, There is such a magic weapon.

Previously, this reaction product stayed in the previous step of passing through the column, and the sample mixing has been completed, and now it can be directly loaded on the column.

Xu Qiu chose two relatively clean ones from the disposable blank columns used before, and completed the sample with Wu Shengnan.

Speaking of this kind of disposable blank silica gel column, Xu Qiu contacted the manufacturer before, and originally wanted to buy a batch. After all, it is very convenient to use, but after asking about the price, the large one is a few hundred yuan, and the small one is better. Dozens of Ruanmei coins, after thinking about it, I still didn’t buy it. It would take up to ten minutes more to fill the pillars by myself, which would save a few hundred yuan. Let’s save some money for Teacher Wei.

After installing the column, Xu Qiu explained to Wu Shengnan while operating the instrument: Our high-pressure liquid chromatograph can achieve a flow rate of 30-60 ml per minute...

The solvent used refers to the developing agent when spotting the plate, and dichloromethane and petroleum ether were selected as the A/B solvents.

Passing through the column was relatively smooth. The two columns of Xu Qiu and Wu Shengnan took a total of more than three hours, and the products were separated and purified. The final yield of the two materials obtained was about 80%.

During this period, Xu Qiu redistilled the tetrahydrofuran (THF) solvent in advance at the same time, and made preparations for the next reaction. Han Jiaying returned from the cryogenic physics laboratory with liquid nitrogen.

Xu Qiu also obtained the device efficiency of the H21 and H22 systems of the junior sister. At the same time, the H22 donor material with sulfur atoms and thiophene side chains was introduced, and the performance was better. Combined with the IDT-T(EH)-ICIN acceptor unit of the senior sister, The highest efficiency reached 7.62%.

Although the increase in efficiency is not large compared to H1x and the original FTAZ materials, the more important thing is to enrich the selection of donor libraries. Afterwards, new acceptor materials will come out, which can be combined with a large number of donor materials at once. Combined, it is easier to achieve a breakthrough in efficiency. This kind of material optimization is difficult to achieve overnight and requires long-term accumulation and trial and error.

With liquid nitrogen, Xu Qiu continued the second step of synthesis of IDTT units, low temperature reaction, and n-butyllithium was used to introduce side chains and hydroxyl groups.

In the field of organic synthesis, there are different ways to achieve the same one-step reaction. For example, in this step, Grignard reagents are also used in the literature, that is, organometallic compounds containing magnesium halides are used to replace the role of n-butyllithium. , the conditions are relatively mild, carried out at THF reflux temperature.

However, the yield of the Grignard reagent reaction was relatively low, only about 30%. In addition, Xu Qiu was more experienced in low-temperature reactions involving n-butyllithium, so he did not change the reaction conditions hastily.

It was the first time for Wu Shengnan to use n-butyllithium, so Xu Qiu gave a demonstration first.

First, liquid nitrogen and absolute ethanol are stirred in a bowl-shaped Dewar to obtain a low-temperature device that can maintain about minus 78 degrees Celsius.

Then, 2.4 grams, that is, 10 mmoles of 1-bromo-4-hexylbenzene, were dissolved in 30 milliliters of redistilled THF solvent, and the reaction bottle was placed under the condition of minus 78 degrees Celsius under the condition of stirring. in cryogenic devices.

Next, 4.2 ml, that is, 10 mmoles of n-butyllithium in n-hexane (concentration: 2.4 M), was slowly injected drop by drop into the reaction flask through a syringe.

After maintaining the low temperature and stirring for one hour, about 1 mmol of the product synthesized in the first step of the IDTT unit was dissolved in 80 ml of THF solvent, and slowly injected drop by drop into the reaction flask.

Finally, the temperature of the reaction vessel was allowed to warm slowly to room temperature and stirred overnight.

Compared with the previous reaction involving malononitrile involving cyanide, the low-temperature reaction of n-butyllithium is much easier for Xu Qiu. Just be careful not to let it be in the air when extracting the n-butyllithium solution. Spontaneous combustion is fine.

The reaction was successfully completed, and Wu Shengnan next to Xu Qiuchao said: This reaction is done, let's continue to deal with the reaction of ICIN derivatives.

Okay. Wu Shengnan nodded, thinking silently in his heart: Working with Xu Qiu, I really don't have a moment to rest. I feel like I have been experimenting all day. No wonder just an undergraduate can publish so many articles. Although it is very hard, But it’s all worth it as long as it pays off.”

Xu Qiu didn't know what the postdoctoral senior sister was thinking. He focused on the reaction devices in the fume hood, and calculated the reaction time of the last step of ICIN-2F/Cl in his mind. It should have exceeded the expected reaction time by more than an hour. , the problem should not be big, and the reaction yield may even be higher.

However, in order to make this reaction more fully, malononitrile is 2 times excess relative to IN-2F/Cl, that is to say, even if the yield is 100%, there will still be a portion of malononitrile, which needs to be Malononitrile disposed of.

As for why IN-2F/Cl is not doubled, it is because IN-2F/Cl is finally synthesized through three-step reactions, and the chemical raw material of malononitrile is very cheap, and the industrial grade is sold by the ton. Yes, tens of thousands of dollars per ton...

High toxicity does not mean cheap. In fact, many highly toxic and dangerous substances are very cheap to buy from laboratories, and they are also easy to handle.

Let’s not talk about the rudimentary ones of disfiguring people by pouring concentrated sulfuric acid. Basically, there will be similar reports every once in a while.

In the poisoning case of Shanghai University that caused a lot of noise before, a medical graduate student was dissatisfied with his roommate because of trivial matters in life, and finally poisoned his roommate, using the highly toxic reagent N-dimethylnitrosamine.

There is another piece of news. It was also a female medical student who stabbed her boyfriend dozens of times. The knife avoided the vitals and was finally identified as a minor injury.

The conclusion is not to easily offend medical students (dog heads).

Xu Qiu has checked the treatment method of malononitrile. For organic cyanide (nitrile), it will be hydrolyzed under acidic conditions to form ammonium salt and carboxylic acid. Malononitrile reacts with hydrogen chloride and water to form malonic acid and ammonium chloride.

Xu Qiu poured the reactant into 30 ml of water, then added hydrochloric acid, kept the pH value of the mixed liquid between 1-2, and stirred for fifteen minutes. At this time, the product ICIN-2F/Cl had been precipitated. Filter through a funnel, wash the product with water and petroleum ether, and dry it in a vacuum oven to obtain a crude product. Among them, ICIN-2F is a pale yellow solid.

In the evening, Xu Qiu chose to stay in Zhangjiang again overnight, and purified the three products of ICIN-2F/2Cl/DM through the column, and finally obtained about 5 grams/5 grams/10 grams of products, with a yield of 70-80%.

This busy work, it was past twelve o'clock in the evening.

On Friday, Han Jiaying left her two materials, H21 and H22, in the Handan campus. She asked senior sister Chen Wanqing to help prepare the devices, and then came to Zhangjiang with Wu Shengnan. The junior sister mainly came to accompany Xu Qiu. After all, she wrote Articles can be written anywhere.

It is worth mentioning that since Han Jiaying’s H22 donor material and Chen Wanqing’s IDT-T(EH)-ICIN acceptor material are both new materials, even if the device performance based on these two materials is not low, it can reach 7.6%. Nor will it be reported directly.

On the one hand, the donor and acceptor materials are all new materials, so it is not clear whether the improvement in device performance is caused by the donor material or the acceptor material; on the other hand, the most important point is that the two new materials It is completely possible to publish two articles, and it is too wasteful to put them together.

After making preparations before the experiment, Xu Qiu and Wu Shengnan continued yesterday's reaction, the synthesis of D units such as IDTT.

Today's experiment pressure is not great, because the three A units have been synthesized, and only the D unit is left.

In the fume hood, the liquid nitrogen in the Dewar bottle has completely evaporated, leaving only a small amount of residual ethanol.

In a fume hood with good air circulation, solvents such as ethanol with a low boiling point evaporate relatively quickly.

Just like drying a damp quilt, even if the sun is covered in cloudy weather, drying the quilt outside is faster than at home, because of the effect of wind.

Xu Qiu poured the reaction liquid in the reaction bottle into water to wash, then extracted with dichloromethane, dried over anhydrous magnesium sulfate, and rotary evaporated to remove the solvent to obtain a crude product.

Immediately afterwards, Xu Qiu directly put the crude product into a reaction bottle, poured 50 ml of acetic acid and 1 ml of concentrated sulfuric acid, heated to 130 degrees Celsius, and refluxed for two hours.

This step reaction is the dehydration and cyclization reaction involving sulfuric acid, which converts the TT-B-TT structure into a TTTBTTT structure, and the target product is the IDTT unit. Compared with the TTBTT structure of the IDT unit, there is an extra T on both sides of the IDTT , the linear conjugate length is also changed from 5 to 7.

As for Wu Shengnan's reaction, it is to convert the TT-BDT-TT unit into TTTBDTTTT, and BDT is actually the structure of TBT, and the target product is the structure of TTTTBTTTT, which has one more T unit than the IDTT unit on both sides, linear The conjugate length is 9.

Of course, the positions of the side chains in the structures synthesized by Xu Qiu and Wu Shengnan are not the same, so the change trend of the specific performance is still unclear. Only after the specific product is obtained and the performance test can be known.

Two hours later, Xu Qiu shut down the reaction and started the post-reaction treatment, which was also washed with a large amount of water, then extracted with n-hexane, dried, and mixed with silica gel.

When referring to the literature, Xu Qiu found that unlike the usual petroleum ether/dichloromethane system, the other party used a mixed solvent of n-hexane/dichloromethane to pass through the column.

Then, after carefully looking at the author's work unit, it was from the beautiful country, Xu Qiu suddenly realized.

Although petroleum ether has an ether in its name, it is not an ether compound at all, but a metaphor to describe its light weight and volatile characteristics. It is a common name used in the petrochemical industry. The main components are pentane and hexane , Octane, these are mixtures of saturated fatty alkanes with 5-7 carbon atoms.

Petroleum ether and n-hexane are similar in polarity, both are very low polarity solvents, and theoretically they can replace each other when passing through the column.

Domestic petroleum ether is more expensive than n-hexane. It is said that the opposite is true abroad, and n-hexane is cheaper than petroleum ether. Therefore, domestic literature mostly uses petroleum ether, while foreign literature mostly uses n-hexane.

Anyway, Xu Qiu couldn't figure out why pure n-hexane was more expensive than the mixture of petroleum ether in foreign countries, but it didn't matter.

In the afternoon, Xu Qiu still chose the petroleum ether/dichloromethane system he was familiar with, and processed the product through the column.

Finally, successfully separated and purified to obtain IDTT material, Wu Shengnan also obtained a BDT-based D unit with a conjugate length of 9, which she named FN.

Returning to the A501 office, Xu Qiu washes his hands while thinking about the next experiment. He still has two steps to react:

Formylation reaction of IDTT unit to obtain IDTT-CHO;

The reaction of IDTT-CHO with several ICIN derivatives yielded the final ADA-type non-fullerene acceptor material.

For these two steps, the senior sister already has a lot of synthesis experience, and Xu Qiu has a system, so the senior sister's experience is his experience, and it is not difficult for him.

However, no matter how simple the reaction is, it takes time to synthesize it.

If the synthesis is forced, one day of overtime on Saturday and another day of work on Sunday, two or three final products can be synthesized, but the time is too fast.

Xu Qiu glanced at Han Jiaying who was working at his desk, and the other party raised his head as if aware of it, and blinked his cute big eyes.

The two looked at each other for a while, and Xu Qiu felt that something in his heart was melted.

How to say that sentence, it's like suddenly having a weakness and suddenly having an armor.

Let's talk about the experiment next week...