Theoretical Study On Triplet Ground State Aromaticity And C-F Bond Activation In Organometallics

Aromaticity,an important concept in organic chemistry,has long attracted the attention of both theoretical and experimental chemists.With the intensive study of aromaticity,different types of aromaticity and aromatic criteria are proposed.For excited state molecules,Baird in 1972 proposed that the annulene in the lowest??*triplet state is aromatic when it has 4n ?-electrons,whereas it is antiaromatic when has[4n+2]?-electrons.There are many related studies on excited state aromaticity,however,the study on triplet ground state aromatic compounds is relatively rare.In addition,few reports on the aromaticity-promoted C-F bond activation are reported.Here we performed the theoretical calculations to investigate the triplet ground state aromaticity and the aromaticity-promoted C-F bond activation,in order to help design organometallic materials applied to photochemical and molecular magnetics and provide new ideas for the activation of C-F bond.The main content includes the following four parts:The first chapter is the introduction part,first,briefly introduces the development and various criteria of aromaticity.Then the current research on the triplet ground state aromaticity and the C-F bond activation are discussed.Finally,the motivations of the projects are proposed.In the second chapter,theoretical studies were carried out to investigate the aromaticity of osmapyridine and osmapyridinium in the lowest singlet and triplet states.The influence of substituents and ligands were considered to tune the energy difference(?EST)of these two compounds.The results show that osmapyridinium with one or two phosphonium substituents can possess triplet ground state character.Furthermore,osmapyridinium with one phosphonium substituent and without substituent display both aromaticity in the lowest singlet and triplet states(adaptive aromaticity).In the third ch apter,the aromaticity of dicupra[8]annulene in th e lowest singlet and triplet states was studied by theoretical calculations.The results demonstrate that dicupra[8]annulene with fluorine substituents has triplet ground state aromaticity.In the fourth chapter,the tautonmerization in Rh compounds was studied by density functional theory calculation to realize the activation of C-F bond.The results reveal that aromaticity can stabilize both the transition states and the products,which promoting the tautomerization to be both thermodynamically and kinetically favorable.