Theoretical Study On The Ligand Effect Of C-O Cross-Coupling Reaction By Ir/Ni Metallaphotoredox Catalysis

The cross-coupling reaction by visible-light-mediated bimetallic cooperative photoredox catalysis greatly increases the possibility of chemists to building carbon-heteroatom chemical bonds,which has a potential development prospects in the field of chemistry and chemical industry.Visible light-mediated photoredox catalysis has gained momentum for the development of new synthetic organic strategies through the implementation of non-traditional oxidation mechanisms,which has become a research focus in recent years.However,due to the limitations of the experimental equipments,many details of the reaction mechanisms need to be further explored.It is worth noting that theoretical calculations of quantum chemistry helps people to understand the mechanism and principle of catalytic reaction.The theoretical method can describe the whole reaction process more thoroughly and deeply,and help to better understand the reaction mechanism.In this paper,photoredox-mediated iridium/nickel dual catalysis for C-O bond cross-coupling reaction and catalyst was studied in detail by means of quantum chemistry theory calculation.In the first chapter,the basic concepts of single-metal catalysis and multi-metal synergistic catalysis,the application of metal and light-mediated bimetallic in the coupling reaction of carbon-carbon and carbon-heterobond are introduced,and the role of ligands in the catalyst is also introduced.The second chapter introduces the theoretical basis and calculation methods,including the introduction of quantum chemistry,transition state theory,redox potential and activation energy barrier of single electron transfer.The third,fourth and fifth chapters of the dissertation are the author's research work during the master's degree.The relevant content is as follows:1.The density functional theory was used to study the ligand effect of metal Ni in the C-O bond cross-coupling reaction catalyzed by Ir/Ni photoredox catalysis.The results show that due to the different coordination of P,N,and O with the nickel center of the metal,the ability of Ni??? to lose electrons is different,and the ability of Ni??? to generate electrons at the same time will also be different,so the difficulty of oxidation addition and reduction elimination is different.First,by comparing the critical energy barriers of reaction potential energy surface of N,O,and P ligands,it can be concluded that N and O bidentate ligands contribute to the processes of oxidative addition and reduction elimination.Subsequently,the difference ??G between the one-step activation energy barrier of oxidative addition and reduction elimination was introduced.When the ??G is smaller,the metal's ability to gain and lose electrons is equal,then the compound of the ligand is more likely to occur in the process of oxidation addition and reduction elimination,so the N-ligand?mobpy?,that is to say,the nickel metal catalyst with N-ligand is more likely to achieve the elementary steps of Ni????Ni????Ni???.By comparing the effects of various ligands on the catalytic ability,this chapter hopes to provide a theoretical basis for the experimental design and development of highly efficient transition metal catalysts.2.The density functional method was used to theoretically study the ligand effect of metal Ir in the cross-coupling reaction of C-O bond by Ir/Ni photocatalysis.The results show that the metal iridium ion complex are composed of main ligands and ancillary ligands.The main ligand mainly regulates the HOMO energy level,and the ancillary ligand mainly adjusts the LUMO energy level.The adjustment of the photocatalyst energy level can make better use of different band light source.Firstly,the Ir??? ground state compound is excited by light to generate the *Ir??? excited state,which causes the first one-electron process to occur with the ground state Ni???complex.According to the calculated redox potential and single-electron activation energy barrier,it can be known that the oxidative quenching process of iridium complexes is greatly affected by the main ligand,and the iridium compound whose main ligand is the donor group is more likely to occur this process.Then,in the second single electron process,the redox reaction of Ni??? and Ir??? is almost barrier free,and the redox potential matches,which is prone to generate Ni??? and Ir???.Then,according to Marcus theory,it is confirmed that the single electron activation energy barrier of iridium complex whose main ligand is a donor group is lower,which is more advantageous for the first single electron process.Finally,the ancillary ligand for the main ligand of the donor group was modified and adjusted to select the appropriate metal Ir complex: the main ligand was [d?CH₃?ppyH],and the ancillary ligand was bipyridine?bpy?.3.Based on the above work,nickel transition metal catalyst and iridium photocatalyst were selected to evaluate the potential energy surface of the synergistic and efficient C-O bond cross coupling reaction.This work not only deepens our understanding of the photocatalysis of C-O bond cross-coupling reaction,but also provides a theoretical reference for the development of novel catalysts,and provides a new understanding and support for the current unknown or elusive mechanism path.