In the 1950s, because the conditions and equipment for the theoretical calculation methods were quite limited, many chemists were committed to synthesizing a larger number and variety of objects. In order to discover better dyeing Cambodia, he has a large amount of time to understand the structure-activity relationship of these organic compounds for a large number of new organic molecules that emerge. So he began to seek answers in the field of computational chemistry, which is the original background of the generation of ideas. In the early 1950s, quantum chemical calculation was still in its infancy, and the complete calculation of molecules was limited to the ancestral training of the diatomic two-electron system. The method of learning is based on a wide range of calculations, and after years of interviews, he began to imagine quantum chemistry methods for the calculation of the electronic spectra of dye molecules. This required considerable courage, because at the time, even a simple molecular spectrum such as ethylene was difficult to explain. They believe that in the new theory, electron repulsion integrals must be introduced in order to predict molecules quantitatively. In 1952, 3 proposed a zero differential overlap approximation, 061; 1 said magic, based on 200 clusters, 38 in the state 1. Machine dye points 1. Found, to. The experimental value of the atomic single-center electron mutual exclusion integral The difference between the valence ionization potential and the electron affinity potential replaces the theoretical calculated value, and a result closer to the experimental value than the ab initio can be obtained. 3, and quantum mechanical integration The quantitative method has brought a major breakthrough to the theory of 7 electrons. In the same year, they introduced the work of Xinjia plus 9 at the State University Molecular and Molecular Spectroscopy Seminar. This work was followed by the administration of the corpse in 193. In the 1 magazine, the basic theory of the same theory studied in 3 is similar to the gizzard method, and it is mainly used to treat conjugated electron molecular systems. Like it, it is different from 10 Li 0, etc., it overcomes the serious defect of completely neglecting the interaction between the two electrons in the 10 gal 0 method, that is, the method considers the interaction of electricity generation. Assuming that the 7 electricity moves independently in a certain average potential field composed of real and other 7 electrons, each elementary electron has the same effective 1 operator of a single electron, so each atom in the available system is perpendicular to the molecular plane The ruler track is a basis function with 9 edges. ， ┕ Hook Shao 5 缱 glaze master, swollen and elegant Li Chi through minimizing the energy of the system to get the 8,083 equation for solving the orbital. On the basis of B, approximate, its matrix element is 1. In other words, the matrix element of the 41 river 1 ratio 0 matrix form, the physical meaning of the matrix expression is as follows: the real integral Coulomb integral, which is often used to exchange integrals for resonance integrals, and is often used to be in surnames, located in 9 and 9, respectively, in the overlapping area The kinetic energy of the electrons and the real attraction energy of the positively charged molecules, 9 is the number of 51 electrons widely distributed in the factory. , The original Guanghe factory. 71 atomic bond levels between atoms. 7B; the orbit and the individual electricity are subject to the repulsion and exchange of 1 electron from the other party; 7, the exchange between the electronic factory and the 7 electron 5 in the heavy state.
The 7-electron theory to solve the 3 equation with the above matrix element is the method. In the actual calculation of the Dan method, it is coincident that the elements 4, 5, and in the matrix element are not directly calculated in theory, but instead Handle empirical parameters. Therefore, parameterization occupies a very important position in the method.
2Parameterization of the PPP method Since the method was founded in 1953, a lot of research has been conducted around the empirical parameters of the method. The approximation of matrix elements is different, the method of parametric quantization is also different, and there are many kinds of parametric quantization schemes.
It is clear from the 1 matrix element Ida formula in method 1 that there are 4 main integrals for parameterization, which are real integrals. The exchange integral where the heart coulomb tributary 1. and the two-center coulomb integral 7 mainly involve the nature of the atom itself, called the atomic parameter, 7 is related to the properties of two connected atoms, called the bond parameter. In the 1960s, I once discussed the parameters of some atoms in more detail. In the early 1970s, 1 and 5, the original 1 parameter bond parameters were also bitten to detect some corpses. 4 The 15 parameter was compared in detail. discussion. In the 1980s, I touched, and made a comprehensive review on the color development of organic dye molecules and Dan calculations, and gave out the atomic parameters and bond parameters of some heteroatom azo molecules. muscle. Qiaohe 1: 1 group still maintains the enthusiasm for the research and method trial. 5. He and his colleagues have improved the calculation accuracy of the specific system molecules by studying the integral parameters of the two-center tunzi repulsion. All these work introduce the configuration interaction 0 to Qiao method 3, and improve the accuracy of the method calculation. The ground state molecule's electric conjugate is subjected to a fixed energy, and the town transitions to the excited state. Electrons transition from different low-energy levels; different high-energy levels constitute a configuration. In the orbit approximation, the spin orbit occupancy is used to describe the state of the multi-electron system. Each occupancy can be used. A Fen determinant describes that some of the calculated 3 wave functions are linearly combined to approximate the true wave function of the molecule. This is the configuration interaction. The introduction of the 6130 abbreviation for configuration interaction takes into account the correlation of electrons. 14. It is helpful to improve the calculation results of molecules, especially the calculation results of molecular excited states, and the accuracy of electron spectrum analysis and prediction. This is very important for us to better understand the properties of molecules, such as Using method 1 to calculate the absorption of fulvene 1 to the longest wavelength at 373 and 233, 1 is less, 1 treatment predicts absorption at 3721 and 24. The experimental values ​​are 3731 and 242. It can be seen that the theoretical calculation results and experimental values ​​are very Match up in recent years. Applying the method of 1: 1 to study the application of the 4PPP method such as benzonaphthylidene-based laser dyes such as benzodiazepines, we know that many functional materials, organic dyes, drug molecules, bioactive molecules, etc. generally have a larger 7-electron conjugate The system, because the foundation of the method is to deal with 7 electronic systems, so it has the characteristics of being particularly suitable for processing organic conjugation and mass production. The Dan method organic conjugate molecular research field has achieved great success.
4.1 The application of PPP method in the study of organic dyes Organic dye molecules are mostly organic conjugated molecules, 7 electrons are very active, 7 electron transitions are mainly related to the ultraviolet light of the molecule, and the fluorescent light is dense. Molecular properties such as favorable means, such as using organic conjugated macromolecular dyes and pigments that can have 7 electrons in ten places, have successfully discussed the corresponding ultraviolet spectrum fluorescence spectrum ground state and excited state electron spectrum of these molecules. 0 volumes have published a more detailed review article in the dyes and pigments magazine in 1982. It is pointed out that to predict the color development and spectral properties of organic matter, one should understand the maximum absorption wavelength of molecules in the range of 1 light, 31; 2 absorption The intensity of the band is very helpful for the selection of effective dyes as chromogenic reagents; 3 the jump dipole direction of the absorption band, this property also has certain practical significance for the research of modern liquid crystal display materials. As another example, through the study of the absorption spectrum of the pentaton dye, we can better understand the difference between the ground state and the excited state of such molecules, thus predicting the difference between the photochemical reaction and the general thermochemical reaction that occur in the excited state. The absorption spectrum of azo-type condensable pigments theoretically confirmed that the pyridone-type monomer exists as a hydrazone. Through the study of ultraviolet spectrum of benzoxazole molecules by using the Qi-1 method, we can understand the mechanism of color development. Find the direction of the molecular yield distance, and provide a theoretical basis for progress to find such new thrown material molecules! 3.
4.2 Application, charge method, study molecular electronic structure and reactivity mechanism The reactivity of the molecule and its spectrum are closely related to the electronic structure of the molecule. From the study of the electronic structure of the molecule, we can obtain the total charge density of the original molecule or the atomic group of the molecule and the chemical strength between the original household. For example, 1 polydiacetylene and its phase compounds are 1 class of typical organic semiconductors. For thousands of reasons, there are many theoretical and experimental studies on this type of polymer. good result. 2 Porphyrins play a very important role in the life process. For example, the complexation of transition metal iron and porphyrins constitutes hemoglobin and myosin white. The key ingredients, the mechanism of electron migration in hemoglobin and myoglobin 3's oxygen-seeking cytochromes, have been widely reviewed by people. The characteristics of the electronic structure, charge distribution, charge migration and other properties of these molecules have revealed the direction of the reaction. The mechanism of charge displacement is given. 3 Benzobazole molecules have a wide range of applications in photosensitive materials and laser dyes. We have studied the photophysical properties of these molecules while studying their electronic structures, and obtained useful information.
4.3 The PPP method is used for molecular design, and prediction of new functional materials and new high-performance materials is the goal that people strive to find. The application of the method can, to a certain extent, enable people to understand the properties of some possible new materials without spending a lot of time doing experiments. He also explored the relationship between the increased ring and the long-wave movement of molecular bands after studying the excited state of a series of polyaromatic hydrocarbons. In order to find the ultra-absorption wave type polyaromatic ring organic production materials, people have paid special attention to the direction of the ferromagnet. The design of high spin score 7 is more striking. It is not easy to synthesize a molecule with a large spin property. Because there are many such molecules and the electron conjugate system, you can use the method to study. 03 et al. Studied the electron density, spin density, electron-donating properties and singlet linear intersystem transitions of such molecules using the open shell method, obtained a lot of information about these molecules, and theoretically designed iron Magnet polymer, with a view to obtaining new magnetic crystals 1. We have designed hundreds of possible new molecules based on the calculation and experimental results of benzo and azole molecules After calculating, after analyzing the properties of the singlet energy change of the electronic structure of the designed molecule, the intensity of the oscillator and the molecular transition distance, some new laser dye molecules are predicted.
5 Limitations of the application of the PPP method Because the method only considers 7 electrons in the molecule, the method also has its own limitations. For example, the width of the molecular absorption band cannot be calculated, and the spectrum similar to the experimentally determined spectrum cannot be obtained from theoretical calculations. . 2 Molecules are often in a specific solvent, and the effects of solvent effect and color-assisted effect cannot be solved simply by calculation. 3 Indefinite number of dyes, such as aggregation and intermolecular interactions, can not be used simply, and the method can be solved by calculation.
Now, the applied research of the method has entered many chemical branches. Due to the introduction of semi-empirical parameters in the processing of molecules, phases and corpses consider some experimental influence factors. In some ways, the calculation results and experimental results are obtained. Better consistency. The method can not only study the ultraviolet spectrum, fluorescence spectrum, phosphorus spectrum, etc. of organic dye macromolecules, but also explore all the properties of various functional materials that are closely related to the 7 electrons. Obtaining conclusions that are difficult to obtain in some experiments, and can improve the understanding of the inner nature of molecules, predict the characteristics of some new molecules, and provide a theoretical basis for the search for new materials. It has become a powerful tool for scientific research by experimental chemists. The organic combination with experiments will surely promote the in-depth development of scientific research.
7 Xin Zhong, Pang Xiaoyi, Huang Deyin. Journal of Functional Polymers, 199645978 Zheng Shijun, Sun Jinguo, Chang Guangjie, etc. Spectroscopy and spectral analysis. 1993, 13325
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