| The main purpose of this paper is to study cyclic alkanes(C3-C6)freeradical ions and Fluorine-substituted benzene radical ions．By means of theB3LYP Density Functional Theory,we did a calculation and into theirmolecular structure,electronic states and the Spin Nature(isotropic hyperfinecoupling constants of a proton(H)value)．Compared with the documentconclusion before,we obtained some new conclusions,Here we will discuss theresearch in this paper by a presenting representatve example of the ionic freeradical．In recent 30 years the neutral free radical has been put much attention by thetheory and experiment chemistries．That is because of their high activity,whichoften acted as an intermediate or initiator in many chemical reactions．Manychemical reactions and life processes have a close relationship with the formationand presence of free radicals,So the reaction induced by free radical plays animportant role in medicine,biochemistry,polymer science,atmosphericchemistry and many other fields．Because of the properties of lack in electronic,the free radical compounds usually have a very short lifetime,so the suitableresearch method to study them is rare．Paramagnetic resonance experiment whichis also called electron paramagnetic resonance(EPR)or electronic resonance(ESR)or electronic resonance(EMR)is the most direct,sensitive methods ofdetecting the free radicals．By the methods of DFT,6-311G(d,p)and 6-311+G(d,p)basis set,we optimized the geometry conformation of the neutral moleculesor ions of cyclopropane,cyclobutane,cyclopentane,cyclohexane,also calculatedthe frequency of these species．And we obtained their energy and the stableconfigurations．Based on the stable configurations we calculated the protonhyperfine coupling constants(a(H))by the methods of MP2 and B3LYP,and thebasic ste of EPR-Ⅱ,EPR-Ⅲ．The calculation has predicted that C3H6+ has a(2A1)configuration,that C4H8+ has a C2h(2Bu)configuration,that C5H10+ has aCs(2A') configuration．C6H12+ has a C2h(2AG)configuration．On the basic ofthe optimized configuration we calculatd the hyperfine structure by the methodsof B3LYP and MP2(full)．The isotropic hyperfine coupling constants of C3H6-,C4H8-,C5H10-,C6H12- haven't been reported up to now．In this paper,wecalculated and predicted the isotropic hyperfine coupling constants (H) and the most stable configuration of them．For the ions of fluorbenzene we obtain theirstable configuration by methods of B3LYP and standard optimization-basedgroups On the basis of their stable configuration,we have calculated isotropichyperfine coupling constants(aH)values by Mp2 and B3lyp．The innovations of this paper are:(1)We calculated the possible stablestructure of the molecule or ion of Cycloalkane by DFT method,and obtained afew new stabile configurations．For instance,form a calculation of Cyclopentane(c-C5H10),we concluded that the most stable configuration is a folded C2configuration．form a calculation of cyclohexane(c-C6H12),we got two stableconfiguration:diagonalization(chair)and C2(vessel type)．Based on the stablemolecular configuration,we got the stable configuration of its ion,and wecalculated isotropic hyperfine coupling constants(H)values．(2)Form ourcalculation,we predicted the free radical ion's structure of fluorbenzene．andalso obtained isotropic hyperfine coupling constants(aH)values．Which lead usto conclution．(3)Through a lot of theothetic methods of the free radical anion andexperimental calculation of basis set,we found a better method to calculate thehyperfine structure of anion system．We thinks that an additional dispersionfunction(+)is necessary when calculating the free radical anion．... |
