Dynamics Study Of HgBr₂ And Imidazoles Molecular System

In this paper,the molecular dynamics of HgBr₂ reaction system and Imidazoles molecular system were studied.The reaction mechanism of the HgBr₂ system and fluorescence sensing mechanism of the Imidazoles system were explained in detail at the molecular level.HgBr₂ reaction system has important research significance in atmospheric physics,atmospheric chemistry and earth environment.The molecular dynamics characteristics of Br+HgBr?Hg+Br₂ reaction are studied emphatically and its reaction mechanism is researched and clarified from both scalar and vector properties based on quasi-classical trajectory theory and corresponding calculation program on the ground state potential energy surface of the system.It is well known that for the dynamics of collision reaction system,not only the scalar properties of the reaction system,but also the vector properties of the system,such as velocity,angular momentum and their vector correlation,should be studied.The results of quasi-classical trajectory calculation show that Br+HgBr?Hg+Br₂ is a typical insertion reaction.During the collision process of reactant molecules,a collision complex with a certain lifetime will be formed.For scalar properties,with the increase of collision energy E_c,the reaction probability and integral cross section decrease,which is due to the deep potential well in the reaction path and the insertion reaction mechanism.The distribution characteristics of product vibration states show that most of the available energy in the reaction process is released in the form of vibration energy at lower collision energy,while only a small portion of the energy can be transferred to the product's vibration energy at higher collision energy.For the vector properties,the product tends to scatter forward in the whole scattering angles;the direction of the product rotation angular momentum j?is perpendicular to the reactant velocity vector k,but the alignment effect is rather weak;when E_c=20 kcal/mol,the product rotation angular momentum j?distributes in the positive direction of the y axis;while when E_c=40 kcal/mol,the alignment of j?along the y axis is not obvious.At the same time,the angular momentum conservation law and related models were used to explain the polarization of products in the reaction system.For the complex molecular system of Imidazoles,we have studied the excitation dynamics of the probe molecule 2-?2-tert-butyldiphenylsiloxy?phenyl-4,5-diphenyl-1-p-tolyl-1H-imidazole by using density functional theory and time-dependent density functional theory.2-?2-tert-butyldiphenylsiloxy?phenyl-4,5-diphenyl-1-p-tolyl-1H-imidazole is a fluoride ion fluorescence sensor probe molecule with high efficiency,sensitivity and responsiveness synthesized recently.The theoretical calculation data of electron absorption and fluorescence emission have been obtained by optimizing the ground and excited state of the probe and the product molecules.The fluorescence sensing mechanism of the probe molecule in fluoride ion detection was elucidated through the study of excited state dynamics.In the process of detecting fluoride ions,the addition of fluoride ions leads to the fragmentation of the Si-O bond of the probe and the formation of Compound-1^–and another product.Then the anionic compound Compound-1^–captures a hydrogen ion from the solution and forms the product Compound-1?enol form?.After being excited by light,intramolecular proton transfer occurs in the excited enol form,forming keto form Compound-1-e.And then the keto form relaxes back to the ground state through radiating fluorescence.At the same time,because this process is exothermic,the fluorescence emission spectra of Compound-1 are obviously red-shifted compared with that of Probe.