Quantum Chemical Study Of The Novel Superhalogen And Its Construction Of Superacid

We systematically studied structure and properties of novel non-classical superhalogen and composite superacids constructed from superhalogen.The main contents,included the design of the novel superhalogen and its verification,construction organic superacid via the protonation of superacid,the calculation of gas phase acidity and the dissociation constants?pK_a?.The first chapter mainly describes the background and significance of superhalogen and superacids.including the main characteristics of superhalogen and superacids,important applications,and recent research progress of the theoretical and experimental.In the second chapter,we introduce the utilized theoretical methods,including the ab initio and density functional methods.In the third chapter,combined ab initio and DFT study is performed in this work to explore the superhalogen properties of polynuclear structures with the ligands of–OH,–OOH and–OF.According to high-level CCSD?T?results,all the structures here are superhalogens whose properties are superior to the corresponding mononuclear ones.Therefore the superhalogen properties of the anions here are still promising and they have an important advantage of high safety,which is crucial for practical applications.An increased degree of structural versatility is imposed by these non-halogen ligands because of the various ways in which they connect the central atoms and their multiple orientations.It is important that this increased versatility will bring new factors,e.g.,the larger spatial extent of the whole cluster and the existence of intra-molecular hydrogen bonds,which should favour high VDE values.These new factors may play an important role in the future search for novel superhalogens.?B97XD,?HF+MP2?/2 as well as M06-2X are capable of providing accurate VDE values,close to the CCSD?T?results.Due to the good balance between the accuracy and efficiency,these methods could provide reliable predictions on large systems which cannot be treated with CCSD?T?or even with the OVGF.In the fourth chapter,the construction route of organic superacids from the combination of organic superhalogens and protons is verified to be a rational one based on a systematic theoretical study covering different planar conjugated backbones,e.g.,[C₅H₅]^-and[BC₅H₆]^-,and electron-withdrawing substituents,e.g.,–F,–CN and–NO₂.In both the gas phase and the solution phase,the acidities of the composites here have a consistent strengthening with the increase of the vertical electron detachment energy of the superhalogen part.Decomposition of the acidity into different contributions further verifies the dominant role of the superhalogen part in the variation of the acidity.Thus,tuning of the acidity of systems of this type could be achieved via rational design of the constituent part of the superhalogen.