to useSingle crystal diffractometerTo cultivate high-quality single crystals, it is necessary to start from multiple aspects such as solvent selection, crystal growth methods, sample pretreatment, environmental control, solvent system optimization, molecular structure characteristics, and operational details. The following are specific explanations:

　　1、 Solvent selection and properties

1. Moderate solubility: The solubility of the solvent in the sample should be moderate. If the solubility is too high, it can easily lead to clustered crystals, while if it is too low, it cannot provide enough solute for crystal growth.

2. Moderate volatility: The volatility of the solvent is crucial for single crystal growth. If the volatility is too high, the solvent will evaporate rapidly, which may lead to rapid crystal growth and a decrease in quality; If the volatility is too low, the growth cycle will be too long and the efficiency will be low.

3. Transparency and temperature conductivity: The solvent should have good transparency to facilitate observation of the crystal growth process; Meanwhile, the temperature conductivity should be good to facilitate the control of the temperature during the production of supersaturated solutions and crystal growth processes.

4. Single solvent and mixed solvent:

Single solvent system: If a solvent with moderate solubility and volatility for the sample can be found, it can be directly used for single crystal cultivation.

Mixed solvent system: When a single solvent cannot meet the requirements, two or more solvents can be selected to create a mixed solvent system with moderate solubility and volatility for the sample. For example, CH ₂ Cl ₂/C ₂ H ₅ OC ₂ H ₅, THF/C ₂ H ₅ OC ₂ H ₅, etc.

　　2、 Crystal growth method

1. Slow solvent evaporation method:

Principle: By slowly evaporating the solvent, the solution reaches a supersaturated state from unsaturated to saturated, resulting in the precipitation of single crystals.

Applicable conditions: Suitable for situations where the sample size is moderate (10-25mg is optimal).

Operation points: Select a solvent with a moderate boiling point (60-90 ℃), gently filter the sample solution with cotton balls, and avoid introducing filter paper fibers into the filtrate; Seal the container with plastic wrap and use a fine needle to poke the hole to control the evaporation rate.

2. Liquid phase diffusion method:

Principle: It enters the good solvent through slow evaporation or liquid-liquid diffusion of poor solvent, changes solubility, and causes crystal precipitation.

Applicable conditions: Suitable for situations with small sample sizes.

Operation points: Adopt layer by layer method, with poor solvent on the upper layer, mixed solvent buffer layer in the middle, and good solvent solution on the lower layer; The optimal ratio of good solvent to poor solvent is 1:2-1:4.

3. Gas phase diffusion method:

Principle: Similar to liquid-phase diffusion method, but solvent transfer is achieved through gas-phase diffusion.

Applicable conditions: It is also applicable to situations where the sample size is small.

Operation points: Choose a suitable solvent system, such as DMF/C ₂ H ₅ OC ₂ H ₅, MF/hexane, etc.

4. Other methods:

Cooling method: By reducing the temperature and solubility, the solution is brought to a saturated and supersaturated state.

Hydrothermal or solvothermal methods: Suitable for compounds that are particularly insoluble, they react under high temperature and pressure conditions to form compounds and grow crystals.

Molten droplet method: Quickly harvest single crystals from molten droplets, suitable for certain specific compounds.

　　3、 Sample pretreatment and purity

1. Sample purity: The purity of the compound should be ensured as much as possible before crystallization, generally reaching 95% or above. But if purification is not possible, it can also be achieved through multiple cultivation.

2. Sample pretreatment: After the sample is dissolved, it should be filtered to remove impurities. When filtering, avoid using filter paper. Instead, gently stuff a small ball of cotton into the lower part of the dropper for filtration.

　　4、 Environmental control and observation

1. Quiet environment: When cultivating single crystals, they should be placed in a place where no one touches them to avoid vibration affecting crystal growth.

2. Regular observation: Generally, it is sufficient to observe once or twice a day, and do not touch the bottle during observation. You can use a flashlight with high brightness to shine and observe the size and luster of the crystal.

3. Timely replacement of solvent system: For obviously ineffective solvent systems (such as the precipitation of large amounts of flocculent solids or powders), the solvent system should be replaced and re cultured in a timely manner.

　　5、 Exploration of solvent system and supersaturation

1. Multi solvent system test: If the sample size is large, it is recommended to evenly divide the sample into multiple parts and test multiple solvent systems at the same time to reduce the cultivation time.

2. Record and Summary: Keep records of each cultivation, including solvent system, temperature, observation results, etc., in order to summarize lessons learned.

　　6、 The Influence of Molecular Structure Characteristics on Crystal Growth

1. Rigid structure: Compounds with rigid structures (such as benzene rings) are more likely to precipitate single crystals than compounds with flexible structures.

2. Alkyl chain length: It is difficult to cultivate single crystals with alkyl chains exceeding 4 carbons in the compound structure.

3. Type of substituent: Chlorinated substituents are generally prone to grow into single crystals.

4. The influence of tert butyl: It is best not to have tert butyl in the molecule, as it is prone to disorder and affects the quality of single crystal analysis.