Calculation Of Organic Inorganic Lanthanide Metal Compounds And Metal Multiple Bonds

Although attempts to synthesize divalent uranium molecules were begun three decades ago,molecular U?II?species isolable in solution have been not achieved until recent years.In this thesis,relativistic density functional theory has been employed to investigate[(U^II)₂?L?]?L is an octadentate polypyrrollic tetraanion?.The structures in various electron spin states?singlet,triplet,quintet,septet and nonet?were optimized.Short distances of U-U?2.32².67??,large bond order?2.95³.90?and high stretching vibrational frequencies(180²63 cm^–1)were calculated.Energetic calculations find that its triplet state is the ground state.It has the electronic configuration of?⁴?²?²,primarily contributed by U?5f?character.Structural and molecular-orbital analyses suggest a slightly weak uranium-uranium quadruple bond,which is confirmed by the quantum theory of atoms in molecule?QTAIM?calculations.Further comparison with analogues[(U^III)₂?L?]²⁺and[(U^IV)₂?L?]⁴⁺was also addressed.It is found that the uranium oxidation state is able to tune the energetic matching between the highest-energy occupied orbital of ligand and the adjacent low-energy metal-based orbital,as well as correlates with the electron transfer between metal and ligand and the diuranium multiple bond number.In addition to the inorganic N-donor polypyrrolic macrocycle,organic cyclopentadienyl ligand has been widely used in the actinide coordination chemistry.In the second part of the thesis,we computationally explored structural and redox properties of complexes[Cp³An^mX]ⁿ?An=U,Np and Pu;m=III and IV;X=Vac,CO,NO,N₂,CO₂,F^–,Cl^–,Br^–and I^–;n=-1,0 and 1?.Mayer bond orders of U-X were calculated between 0.20 and 1.50.The assocation with QTAIM analyses attributes U-N?NO?to a covalent double bond,while a dative single bond for other U-X.Considering both solvation and spin-orbit coupling effects,the reduction potential?E⁰?was calculated upon reducing complex from+IV oxidation state to+III.For cases of X=halogen,the calculated E⁰ value increases in going from F,Cl,Br to I,which indicates the increased reducing ability of complex.When X is small neutral molecule,their E⁰values were calculated to be larger than those of halides,where the E⁰ of X=NO is the largest one.Along with U,Np and Pu,their E⁰ values were calculated to be increasing,which well reproduce the experimentally measured results of An^IV/An^III ions.