Theoretical Investigation On The Decomposition Of Nitroimidazole?methylnitroimidazole And Trinitrotoluene Triggered By Low Energy Electrons In Gas Phase

When the radiation occurs.The single strand or double strand of DNA will be broken.When biological tissues are exposed to high-energy radiation,the molecules would be ionized,thereby generating a large number of secondary low-energy electrons that attached and interacted with biomolecules,causing the breakage of certain chemical bonds in the molecules.low-energy electrons not only induce radiation damage to DNA molecules and certain biological tissues,but also induce damage to certain chemical molecules,thus resulting in the breakage of chemical bonds in the molecules.In this paper,quantum chemical methods were mainly introduced into present investigation of the dissociative electron attachment of Nitroimidazole,Methylnitroimidazole and Trinitrotoluene,which were implemented on the Gaussian 09 and Multiwfn package suits.This article is divided into four chapters.In the first chapter,the brief history and prospects of application for quantum chemistry are first described.Then,the progress of dissociative electron attachment was also briefly introduced.Finally,the principle achievements of this article were illustrated.The second chapter predominantly deployed the knowledge of quantum chemistry.In the light of the above theories,this article made great contributions to theoretically detailed exploration of the selected research system in Chapters 3 and 4.In the third chapter,the target of this article is analyse the decomposition mechanism of Nitroimidazole and Methylnitroimidazole which was induced by low-energy electrons.Using density functional theory calculated under UCAM-B3LYP/aug-cc-p VTZ level.The neutral molecules of 4-Nitroimidazole(4NI),1-Methyl-4-Nitroimidazole(Me4NI)and 1-Methyl-5-Nitroimidazole(Me5NI)were optimized.The vertical electron affinity,adiabatic electron affinity of molecule,vertical detachment energy of anions,the configuration changes of mentioned molecules during the chemical reactions and the dipole moment and charge distribution before and after low-energy electrons attached were systematicallyanalyzed,thus,the location of the breakage of the chemical bond was determined.The results indicated that low-energy electrons are attached to the lowest unoccupied orbitals of 4NI,Me4 NI,and Me5 NI,forming a ?-type single electron occupied molecular orbital.The origination of hydrogen radicals is due to N-H bond in 4NI is easily to dissociate into fragment and the C-NO2 bond dissociates to generate NO2 radical is more difficult than dissociating NO2-,In addition,the reaction involves not only the breakage of single bonds,but also the more complicated bond breaking process.Finally,it was confirmed that Me4 NI is more accept an electron to induce the breakage of intramolecularly chemical bonds.In chapter four,the mechanism of low-energy electron-induced decomposition of Trinitrotoluene in gas phase under the B3LYP/aug-cc-p VDZ level was investigated.Using above method,the vertical electron affinity and adiabatic electron affinity of Trinitrotoluene were calculated.The alternations of the configurations during the reaction,the changes of the dipole moments before and after the low-energy electrons attached to TNT were analyzed and discussed.The changes of electron density on the surface of the molecules during transient anion formation were analyzed by Multiwfn program.The frontier molecular orbital analysis shows that low-energy electrons attached to the lowest unoccupied molecular orbital of TNT and formed ?-conjugated single electron occupied molecular orbital.In addition,the decomposition energy of transient anion into NO2 radicals is larger,when compared with the corresponding energy of anion transient anion into NO2-.The process of other bonds is more complex,which required more further investigations.The calculation results confirmed that low-energy electrons plays an significant role in inducing the breakage of chemical bonds in TNT molecules.