Theoretical Study Of The Structure And Chemical Bond Properties Of Bimetallic Actinide-platinum Complexes

Heterobimetallic actinide-transition metal complexes have abundant active centers and likely metal-metal bonding interaction,which make their electronic structures rather complicated and electronic transition extremely diversified.Recently,the ultilzation of inverse trans influence（ITI）has successfully guided to synthesize novel actinide complexes that are supposed to thermodynamically unstable,enriching actinide chemistry.Those complexes,however,are mainly limited to the involvement of high-valence actinide and/or metal-ligand multiple bond.Examples containing both low oxidation state actinide and metal-metal single bond remain rare.In the thesis,density functional theory（DFT）was employed to explore families of actinide-group 10 metal complexes supported by bidentate phosphinoaryl oxide ligands.Firstly,a series of uranium-group 10 metal complexes of bidentate phosphinoaryl oxide ligands have been designed by varying TM（Ni,Pd and Pt）,uranium oxidation state（IV and III）and axial donor（I,Br,Cl,F,Me₃SiO and Vacant）.Calculations demonstrate an intrinsic TM→U dative single bond.The order of bond strength of U-Ni>U-Pt>U-Pd is suggested by QTAIM（quantum theory of atoms in molecule）data,interaction energy(E_int),formal shortness ratios（FSR）and bond orders calculated at various levels of theory,revising the previous result where U-Pt is the weakest.It is further evidenced by relativistic effects of heavy metal,natural orbital population and electronic spectroscopy.Regarding U-Ni complexes with different axial donors,metal-metal distances are found to be linearly correlated with QTAIM data/E_int/bond orders.Experimental UV-vis-NIR spectra were well reproduced by time-dependent DFT calculations.Complicated visible-light absorption bands,whose understanding remains unclear for many experimentally known heterobimetallic complexes,were rationalized in the work,along with NIR bands assigned as 5f→5f transitions.Secondly,over twenty actinide-transition metal complexes have been designed via extending uranium to other actinide like thorium,protactinum,neptunium and plutonium.The relativistic DFT study of structural,bonding and electronic properties reveals the order of ITI stabilizing actinide-metal bond.Computed electron affinity values,related to the electrochemical reduction,linearly correlate with experimentally measured reduction potentials.Although showing the same ITI order for X donors as a previous study did,the regularity built by the electrochemical reduction does not work for actinide changes.The reduction is primarily of an actinide-based mechanism with minor participation of transition metal and phosphinoaryl oxide except for thorium-nickel complexes.Changes of molecular properties upon reduction were also addressed.