I Have a Research Support System

Xu Qiu was very interested in introducing the cyano group. He had investigated the knowledge related to cyanide before, and it happened to be used at this time.

"Inorganic cyanide, such as inorganic salts such as sodium cyanide and potassium cyanide, is indeed very toxic, and a small dose will cause farts.

However, if the cyano group is to be used, the organic cyanide is used, which is relatively less toxic. For example, the commonly used acetonitrile solvent is only moderately toxic.

The principle of cyanide poisoning is that free cyanide ions can inhibit the activity of various enzymes in cells in the body, causing the cells to die of hypoxia and suffocation, and the amount of organic cyanide dissociated into cyanide ions in the body is not large.

Even so, if you directly contact or inhale a large amount of organic cyanide vapor, there are still great dangers, including the introduction of fluorine atoms, which also involves the use of fluorine reagents.

In short, I just make a suggestion, and how to do it depends on your own ideas. "

"Okay, I'll think about it again," Chen Wanqing nodded, "Let's synthesize the C4 molecule according to the existing design today."

A502 Laboratory.

The DEBUFF that reduced work efficiency has disappeared, and Xu Qiu is full of energy, preparing necessary equipment such as glass instruments and magnetic stirrers.

The two improvement paths he chose were fused cyclization and the introduction of heteroatoms - selenium.

For the newly synthesized 3D-PDI molecules, the central core unit and the surrounding PDI molecules are connected by "one" carbon-carbon single bond.

The carbon-carbon single bond can be rotated, so the molecular structure is not fixed, forming a variety of molecular conformations, which will destroy the conjugated structure of the entire molecule, which is not conducive to the charge transport within the molecule.

The fused cyclization is to connect the nuclear unit and the surrounding PDI molecules through "two" carbon-carbon single bonds, which can stabilize the molecular conformation and improve the conjugation of the molecule.

For example, if two people hold hands, just holding hands with one hand, it is very convenient to move around, and many postures can be unlocked;

But if both hands are pulled together, the posture of the two people will be restricted, and it will be very difficult to play any tricks.

The idea of ​​fused cyclization is essentially imitating the spherical structure of fullerene C-60.

The entire molecule of C-60 is a condensed ring structure, and the conjugated system on the surface of the sphere is connected as a whole, and the ability of charge transport is very strong.

Another method of introducing selenium atoms is an idea Xu Qiu found based on existing literature, which can be regarded as putting new wine in old bottles.

In organic photovoltaic materials, the introduction of sulfur, selenium, fluorine and other elements may improve the photoelectric performance of the material. It is difficult to introduce fluorine atoms here, so he finally chose selenium.

As for the specific principle of photoelectric performance improvement, there is no unified statement in the academic circle.

Many questions are unanswered at this stage, but it does not prevent people from applying them.

...

Start experimenting.

The first reaction is the photocyclization of PDI3-B-5.

The raw material used is PDI3-B-5, iodine is used as a catalyst, the solvent is toluene, the conditions are normal temperature and light, and the reaction time is 24 hours.

First redistill the toluene, then add the remaining tens of mg of PDI3-B-5 material in the reaction vial.

The reaction of small molecules does not require a high amount of solvent, so Xu Qiu added 15 ml of double-distilled toluene to the reaction flask to dissolve the raw materials.

Next, 1 mg of elemental iodine was added.

Finally, put the device under the irradiation of high-pressure mercury lamps. Many street lamps on the street are high-pressure mercury lamps, which have the advantages of low cost, high luminous efficiency, long life, and power saving.

This reaction should be the simplest reaction since Xu Qiu did the synthesis experiment. It took almost no effort, and it was completed without any danger.

The only downside is that the response time is a little longer, and it takes a whole day to wait.

The second reaction is the selenization reaction of PDI3-B-6, which is divided into two steps. The first step is to introduce a nitro group at the bay position of the PDI molecule, and the second step is to replace the nitro group with a selenium atom.

In the first step of the reaction, the raw materials are PDI3-B-6 and concentrated nitric acid, the solvent is dichloromethane, the condition is normal temperature, and the reaction time is 8 hours.

This time, instead of redistilling the solvent, add the weighed PDI3-B-6 material and 10 ml of dichloromethane directly into the reaction flask.

Then, dissolve 3 ml of fuming nitric acid in 5 ml of dichloromethane. The so-called fuming nitric acid is a liquid with a nitric acid concentration of 90%-97.5%. Extremely strong, it can be used as rocket fuel.

Because of the high danger of fuming nitric acid, Xu Qiu deliberately put on an extra layer of gloves when taking it, and pulled the glass of the fume hood to the bottom, and then unscrewed the cap of the reagent bottle.

Even so, there is still a hint of sour taste leaking out.

After the prepared fuming nitric acid was dissolved, Xu Qiu slowly dripped the solution into the reaction bottle, adding drop by drop, but only 0.3ml was added.

Finally, add a magnetic stir bar and stir at room temperature.

Two responses were submitted and it took less than an hour.

The reaction route was designed by Xu Qiu himself, and the reaction conditions were summarized based on literature.

Although most organic reactions have relatively general reaction conditions in textbooks, for specific and highly specialized molecules, such as the synthesis reaction of PDI, the guidance of literature is of great significance.

If there is no literature reference, it may take three to five days, or even a week or two, to just explore the conditions.

However, his molecular structure is only similar to that in the literature after all, not exactly the same.

Therefore, Xu Qiu has no idea about whether he can get the desired result in the end.

As for using the power of the system, such as the simulation laboratory I, it is not very suitable.

Currently he has Simulation Lab II, and Simulation Lab I is rarely used.

The main advantage of the latter is that it can be accelerated, and such a reaction time of 24 hours, forcibly spending 2400 points to accelerate to verify the feasibility is too cost-effective;

If the reaction time is relatively short, there is no need to speed up, because there is a fixed time cost for investing in the reaction, so it is better to invest in reality.

The only remaining advantage of Simulation Lab I may be that it does not need to consume materials, which can save experiment costs.

But materials like PDI are cheap and can be made at will.

Save money or something, it doesn't exist.

After submitting two responses, Xu Qiu wandered around the lab for a while, seeing that neither of the seniors and juniors seemed to need his help, and returned to the office.

...

Time passed, and it was night.

Because of the big lightbulb of senior sister, Xu Qiu and Han Jiaying didn't act too presumptuously in the office, and spent most of their free time writing reviews seriously.

At present, Xu Qiu's progress is very fast. He has completed the second part of the PDI content he is in charge of, and is integrating with the A-D-A part that the senior sister is in charge of.

According to the school girl's words, she was a little bit close, and she didn't know if it was true or not.

The first nitration reaction time of the second reaction is up.

Xu Qiu went to the laboratory for post-reaction processing.

He was dumbfounded when he saw the results of the spotting.

One, two, three... sample points.

"Fuck."

"Brother, what's the matter?"

"The experiment failed."

"Do you need my help?"

"No, you can continue to pass the pillar."

"Okay."

Xu Qiu is very calm, he knows that the failure of experiments is the main theme of scientific research.

It's just that he hasn't tasted such a taste for a long time, and he really misses it.

‘Now that the fact has happened, the most urgent task is to find the reason for the failure of the experiment, and then improve the experimental route or method. '

'So, what's the problem? '

Xu Qiu shrunk his nose, smelling the faint smell of solvent in the air.

This is a unique smell in organic laboratories, because there are a lot of solvents that have been opened, even if there is a gasket on the bottle cap, a small amount of solvent will escape from the gap.

Therefore, the ventilation of the laboratory is very necessary, otherwise chronic poisoning is unavoidable in such an environment for a long time.

Even wearing a gas mask, solvent vapors can still penetrate the body through the surface of the skin.

The laboratory is not a suitable place for thinking, so Xu Qiu greeted the junior girl and returned to the office.

Chen Wanqing was wearing earphones to watch the show, she looked up at Xu Qiu, then lowered her head, and locked her eyes on the computer screen again.

Xu Qiu washed his hands, returned to his desk, turned on the computer, checked the synthesis route of his reaction, and began to analyze:

The conditions for nitration substitution with fuming nitric acid are already very violent. It stands to reason that PDI molecules should not be able to resist the attack of nitric acid molecules, and it is easy to obtain trinitro-substituted products.

Each PDI molecule has two reaction sites at the same position, because it is on the same side, only one nitro group can be added, even if...

No, not two reactive sites, but three, because the central benzene ring and the PDI molecule next to it are connected by a single bond, which means that there is an additional bay-positioned reactive site on the other side.

Among the three reaction sites, the outer one has a high chance of being substituted, while the inner one has low reactivity due to steric hindrance, but it is not low, that is, three, four, five, and six substitutions may be formed.

It turns out that there are so many possible products, no wonder there will be a row of sample points on the spot plate.

How to improve it?

Either change the nitration reaction and replace it with other groups, or weaken the conditions of the nitration reaction to reduce the reactivity of the central high-steric hindrance region, or reduce the number of reaction sites for each PDI molecule to two.

The third option, it seems...just right for the photocyclization reaction.

If photocyclization is carried out first, so that the central position of the molecule becomes a fused ring connection, and then nitration is carried out, there is no need to worry about the inner reaction site, because it has disappeared.

Hey, it's a pity that this pot of reaction raw materials is lost.

After finding out the reason, Xu Qiu returned to the laboratory.

First dispose of the failed reaction, and then look at the other pot, the iodine-catalyzed photocyclization reaction.

He clicked on the board and looked at it. The raw material spots were relatively shallow. Although there were two or three shallow sample spots, the color of the main product spots was relatively dark, which meant that the current production rate had almost exceeded 50%.

There is a high probability of success, Xu Qiu is determined.