Theoretical Study Of Molecular Structure And Hyperfine Structure Of Radical Ions

The present work is the continuous one, closely connected with Dr. Liu Ya-Jun's. The main species studied are included 1-pentene cation (l-C₅H₁₀⁺), 2-pentene cation(2-C₅H₁₀⁺), 1-hexene cationO-C₆H₁₂⁺), 2-hexene(2-C₆H₁₂⁺), 3-hexene(3-C₆H₁₂⁺), cyclobutane cation(c-C₄H₈+) and bicyclo[2,2,l] hexptane or norbomane and sulfur oxide anions(SO₂^-, SO₃^- ), Whose molecular structure, electronic states, adibatic electron affinities and spin properties(proton isotropic hyperfme coupling constants a(H) values) have been calculated. Here are several representative ions listed to set forth the research course of the present work.Hydrocarbon radical cations form a fundamental class of compounds with a variety of intriguing properties and reactivity intermedium in chemistry and biology chemistry. Many chemists have been attaching importance to them. In previous papers there are many research work about the theoretical study of the ethene and propylene cations, which of the hydrocarbon four and more carbon atoms have been rare, otherwise. Lunell and et al carried out ab intio hyperfme structure studies for radical cations of various kinds of hydrocarbon, and they used the (U)HF (Hartree Fock theory) and (U)MP2(second-order unrestricted Moller-Plesset perturbation theory [12,13]) methods in the geometry optimization calculations and the SDCI method for the hyperfme structure (a(H) calculations.Here density functional theory B3LYP method, together with 6-31G(d,p), 6-31+G(d,p), 6-311G(d,p) and 6-311+G(d,p) basis, has been used. The molecular geometries for various conformations of the pentene and hexene cations have been optimized, and the frequency analysis calculations are performed at the B3LYP/6-311G(d,p) level. The most stable geometries are concluded. l-C₅H₁₀⁺ ion is predicted to have a nonplanar structure, which is in contrast to the previous conclusions based on ab initio calculations. At the same time, except for the planar 2-C₅H₁₀⁺ , the nonplanar geometry is found, but itsenergy is close to the planar one. Based on the B3LYP optimized geometries, the proton isotropic hyperfine coupling constants ( hfcc's ), a(H) values have been calculated at the B3LYP and MP2(full) levels. The calculated isotropic hfcc results of 2-C₅H₁₀⁺ and 3-C₆H₁₂⁺ are in good agreement with experimental data and more accurate than the previous theoretical results. No experimental hfcc data are available for 1-C₅H₁₀⁺, l-C₆H₁₂⁺ and 2-C₆H₁₂⁺ ions. The hfcc's and the most stable structures for three are predicted in the present work. The potential e0nergy surface of the cyclobutane(c-C₄H₈) radical cation has been explored at the B3LYP method with all the kinds of standard basis sets. The electron vertical and adiabatic affinities calculations are very near to the experimental data. At B3LYP level the parallelogram and rhombus and rectangle geometries of its radical cation(c-C₄H₈+) are optimized. It is concluded that the parallelogram geometry, not the thomboidal one, is the most stable one energetically. And the isotropic proton hyperfine coupling constants(a(H)) of pucked parallelogram geometry are in good agreement with experiment.Sulfur oxide compunds have previously been proposed as important intriguing substances and reactive intermediate in oxidation process. Experimentally, the gas isolated SO₂^- and SO₃^- species were reported, together with their molecular structure and hyperfine coupling constants. The adiabatic electron affinities of the corresponding neutral molecules were also determined on the experiment. In the present work the molecular geometries, the proton isotropic hyperfine coupling constants (hfcc) of SO₂^- and SO₃^-, and the adiabatic electron affinities(AEAs) of the corresponding neutral molecules have been calculated by performinig the quadratic CI calculations including single and double substitutions (QCISD) with the 6-311G(d), 6-311+G(d), 6-311G(2d) and 6...