Ab initio design of several nitrogen-containing organic dyes and their tautomerism based on quantum mechanical calculations

(M.SC) Thesis for Master's Degree

Orientation: Organic

Abstract of the thesis (including summary, objectives, implementation methods and obtained results):

Computational chemistry using computer software is a powerful tool in the design of molecules with special properties Computational chemistry is a general and general term that includes a wide range of methods and approximations and solves chemistry problems using mathematical laws and theory. Today, quantum mechanical calculation methods are considered as an important tool in chemical research because they have the ability to calculate and predict the energy of the structure and other features in the molecule. In fact, computational chemistry is a branch of science related to the analysis and measurement of properties of materials that cannot be directly measured, and they benefit from sciences such as mathematics and statistics, while the obtained results complement the information obtained from chemical experiments.

Among the software and programs that are used in this research are Gaussin 98, Gaussview, and Chemoffice software.

by these softwares, the design of several groups of nitrogen-containing organic dyes and their tautomerism, as well as the effect of exochrome groups in terms of stability, is done based on Ab initio quantum mechanics calculations by DFT command, opt+freq, HF/6-31G, the value of HF formation energy, HOMO energy, the highest filled molecular orbital (orbital that acts as an electron donor, which is the same external the most filled layer with the highest energy level), the LUMO energy level of the lowest empty molecular orbital (the orbital that acts as an electron acceptor, the innermost empty layer with the lowest energy level) and ?max and the H-L difference are calculated.

For this purpose, the structure of the desired compounds is first drawn, and then the structure of the compounds is optimized by using the relevant software and also choosing the appropriate command, and in the next step, the amount of formation energy of the compounds is checked. .

The aim of this research is to investigate the effect of heteroatoms on the stability of organic dyes, in such a way that by replacing some heteroatoms and calculating HF for the tautomerism of each molecule, the stability of tautomers is determined. Textile, plastic, paper making and . are used.

Color has existed since the beginning of the history of human life, so that early humans and cave dwellers used red soil as red color, white mud as white color, and black coal as black color. The use of color at the beginning of human civilization was for its attractiveness and beauty and it is said that it dates back to five thousand years before Christ. The Egyptians were the first creators of blue color from copper sulfate, red color from mercury sulfur, and yellow color from arsenic. Henry Perkin, a chemistry student at Royan College, was discovered. He tried to structure the drug guinein from aniline (a chemical found in coal) and as a result of the experiment, a thick black sludge was produced. He tried to dye silk with it, which was a stable color resistant to washing and fading against light.

After the discovery of the first synthetic dye in the middle of the 19th century, chemists became interested in discovering the relationship between the dye and its molecular structure. In recent years, the issue of the origin of color in organic molecules has been scientifically analyzed. In addition to that, the knowledge of colors and how to create them, nowadays, is very important in design..

In the early days of dye synthesis chemistry, there was very little knowledge about the structure of organic molecules. After Kekule's hypothesis about the structure of benzene was proposed, organic chemistry made rapid progress. New colors in the market have been created from Kekule's research method on the molecular structure of benzene in 1868.

At the beginning of the 20th century, synthetic colorants were completely replaced with natural colors

2-1-1 General definition of color

The dyeing industry has a long history. Many consumer products in advanced societies are dyed in order to have a beautiful appearance with general appeal and acceptable for final consumption.

Colors are diverse in terms of application and they may be classified according to their chemical structure or application methods, for example, in dyeing and printing textile products, plastic dyeing, etc., but none of the methods of classifying colors is completely satisfactory, because there may be several types of colors that have different physical properties and also how to use them. have the same chemical structure. However, the use of each of these classifications in turn is necessary and helpful in many situations.

Fundamentals of color chemistry

1-2-1 Physical definition of color

Color is a change in symptoms that appear when the retina of the eye is affected by electromagnetic radiation. They are stimulated in the wavelength range of 380 to 760 nm. White light means radiation that is spread almost uniformly in the range of 400 to 800 nm. If it passes through a prism, it breaks down into color spectrums, so that seven colors: violet, blue, indigo, green, yellow, orange, red, can be easily recognized in it. Computational Chemistry is a general term that includes a wide range of approximation approaches. Use rules to solve problems with mathematics and theoretical chemistry deals. Today, quantum mechanical computation methods are important tools in researches related to chemical science because they have the ability to calculate and predict the energy of the molecular constructs and other specialties of the molecules. This analysis helps to understand which molecules are appropriate for laboratory researches or what molecules have required stability to form. in fact Computational chemistry is a branch of science in relation to the measurement and analysis of the properties of materials that are not directly measurable and use sciences such as mathematics and statistics while results complete the data come from chemical experiments.

Including software and programs that are used in these researches are Gaussian 98 and Gaussview and Chemoffice.

By these softwares, design and evaluation of some classes of nitrogen-containing organic dyes and Tautomery survey and also effect of oxochrom groups in terms of their impact on the stability based on Ab initio quantum mechanical calculations are done. By order DFT, opt+freq, HF/6-31G can calculate content of energy to form HF, energy of HOMO-highest occupied molecular orbital-(orbital that acts as an electron donor to fill the outermost layer of the highest energy level), energy level of LUMO-lowest unoccupied molecular orbital-(orbital acts as an electron receiver, the innermost empty layer with the lowest energy level), ?max, and H-L difference.

Therefore, the structure of the compounds is plotted first. And then using the relative softwares and select the appropriate commands, structures of compounds would be optimal. In the next step, the formation energy is investigated