Study on the Synthesis of Charge Transfer Complex of Nifedipine and Tetracyanoethylene

Purposes: To construct a new method for the determination of nifedipine and apply it to the determination of in vitro drugs in order to achieve simple and accurate quantitative detection. Procedures: A charge transfer complex of nifedipine tetracyanoethylene was constructed, and the fluorescence intensity changes of the complex and nifedipine were compared. Screen the effect of drug dosage, reaction time and reaction temperature on the fluorescence intensity of the system. Results: Nifedipine is a substance with its own fluorescence characteristics, but its own fluorescence intensity is not as high as expected. Through the addition of tetracyanoethylene, it is found that the fluorescence intensity of nifedipine has been greatly enhanced, combined with ultraviolet A new absorption peak was found in the spectrum, indicating that the two were successfully complexed. Conclusions: The experiment successfully synthesized the nifedipine charge transfer complex, and constructed a new method for the determination of nifedipine content, which is of great significance for the determination of the content of drugs in vitro.


Introduction
Since my country's entry into a well-off society, the awareness, treatment, and control rates of hypertension have been quite low. Hypertension has seriously threatened the physical and mental health of the human body [1][2][3] . Therefore, the prevention, diagnosis and treatment of this disease has been widely adopted by the whole society attention. In medicine, hypertension is characterized by the continuous increase of arterial blood pressure, which can be accompanied by the occurrence of organ function or organic damageAccording to whether the cause is clear, it can be divided into two types: primary hypertension and secondary hypertension. Surgical treatment and medical treatment are targeted treatment methods based on the conditions caused by the cause. Usually, antihypertensive drug therapy is the more common treatment. Nifedipine, as a kind of antihypertensive drug, plays an important role in the treatment of hypertension. Up to now, scientific researchers have worked tirelessly to develop a variety of blood pressure lowering drugs. While these drugs enter the human body to exert their efficacy, they also produce certain toxic side effects that affect health [4] . Therefore, it is of great significance to establish an optimized analytical method for the determination of nifedipine drug content [5][6][7] . There are many methods to determine the content of nifedipine. This project mainly uses fluorescence analysis to determine the content of nifedipine. As a commonly used analytical method in the laboratory, fluorescence analysis is simple and efficient. It is more widely used than mass Absolute ethanol. Preparation of nifedipine standard solution, and 5×10 -3 mol/L tetracyanoethylene standard solution Accurately measure 2.5 mL of tetracyanoethylene and an appropriate amount of nifedipine solution in a 10 mL colorimetric tube, dilute to volume with absolute ethanol, shake well, heat in a constant temperature water tank at 40°C for 40 minutes, and cool the sample to room temperature. Measure the excitation wavelength at 435 nm, record the fluorescence intensity, and repeat the above operation method for comparison.

Spectral Analysis of the Charge Transfer Reaction of Nifedipine
Scan the fully reacted nifedipine-tetracyanoethylene charge transfer complex, and measure the fluorescence spectra of nifedipine working solution and tetracyanoethylene working solution under the same conditions as a control group. Place the fully reacted test solution in a quartz cuvette, use distilled water as a calibrated UV spectrophotometer to scan the UV characteristic peaks, and use equal amounts of nifedipine working solution and tetracyanoethylene working solution as controls , Draw the absorption spectra of the three, and determine the location of the strong absorption peak of the charge-transfer complex.

Single Factor Experiment
The best effect of fluorescence intensity was determined by single factor experiment to investigate the dosage of tetracyanoethylene, the dosage of nifedipine, the reaction temperature and the reaction time. 2.3.2. The impact of nifedipine dosage. Take 1-8 mL of nifedipine solution and add it to a colorimetric tube containing 0.5 mL of tetracyanoethylene, make the volume constant with ethanol, shake well, and heat in a water bath at 40°C for 40 min at a constant temperature, and measure at 435 nm. Its fluorescence intensity determines the best dosage of nifedipine.

The influence of reaction temperature.
According to the experimental method, under the condition that other experimental conditions are fixed, the fluorescence intensity of the charge transfer reaction between nifedipine and tetracyanoethylene in a water bath at 30°C-60°C is measured to determine the optimal temperature required for the experiment.

Effect of reaction time.
Under the determined temperature conditions, different time periods with a reaction time of 10 min-50 min were selected to observe the fluorescence spectrum to determine the best time.  Figure 1. It can be seen from the picture that the nifedipine solution itself has certain fluorescence characteristics. When nifedipine interacts with tetracyanoethylene to form a charge-transfer complex, the fluorescence intensity of the complex is significantly enhanced. Take out the completely reacted test solution in a quartz cuvette, use distilled water as a calibrated UV spectrophotometer to scan the UV characteristic peaks, and take equal amounts of nifedipine working solution and tetracyanoethylene working solution as controls Group, draw the absorption spectra of the three as shown in Figure 2. Nifedipine has a characteristic absorption around 400 nm, tetracyanoethylene has a characteristic absorption around 250 nm, and the complex has a characteristic absorption around both wavelengths. The characteristic absorption indicates the formation of charge transfer complex.