The Theoretical Studies On The Structure, Hyperfine Coupling Constants And Electron Spin Density Of Some Small Molecules And Their Ions

The purpose of this paper is to study the structure and topological properties of electron density of radical cations containing N atoms,interstellar molecules and interstellar molecular ions by quantum chemistry and topological analysis of electronic density.Meanwhile,we study the hyperfine coupling constants and spin density of the atom in the ions.Moreover,It provides the theoretical foundation for the further research of electronic spin paramagnetic resonance spectrum.In this thesis,the linear relation between hyperfine coupling constants and spin density of N atom which was included in the organic radical cations was discussed. And the hyperfine coupling constants and spin density of interstellar molecular ions were predicted.There are six chapters altogether.The theoretical and experimental research on organic radical cations containing N and interstellar molecular ions in recent years were summarized in the first chapter.In the second chapter,the application of quantum chemistry,the theory Atoms in Molecular theory(AIM),the basic principle of electron spin resonance was summarized.In the third chapter,two calculation methods were used to obtain stable structure of organic radical cations containing N atoms,and find the linear relation between hyperfine coupling constants and spin density of N atom.In the fourth chapter,three calculation methods were used to get the hyperfine coupling constants with different symmetries of CH₃OH,CH₃OH⁺,CH₃OH^-,CH₃SH,CH₃SH⁺,CH₃SH^-,also study on their topological properties of electronic density.In the fifth part,three calculation methods were used to obtain the hyperfine coupling constants with different symmetries of CH₃CN,CH₃CN⁺,CH₃CN^-,CH₃NC,CH₃NC⁺,CH₃NC^-,also study on their topological properties of electronic density.In the sixth part,two calculation methods were used to study the hyperfine coupling constants with different symmetries of CH₂CHCN,CH₂CHCN⁺,CH₂CHCN^-,CH₃CH₂CN,CH₃CH₂CN⁺,CH₃CH₂CN^-,also study on their topological properties of electronic density. The innovations of this work are:1.There is a linear relation between the hyperfine coupling constants and electron spin density of N atom which is included in the organic radical cations.2.The stable structure and hyperfine coupling constants of molecular ions which have been predicted to exist possibly in interstellar space.The results of these calculations will provide new theoretical information for the observation of radio astronomy and the discovery of new interstellar molecules.3.The electron spin densities and integral net charge of interstellar molecular ions were studied using the topological analysis of electronic density.